i 

 

 

 

A conceptual framework to improve the reporting quality of strength training 

exercise descriptors in anterior cruciate ligament reconstruction rehabilitation 

programs 

Arnold Vlok 

Student no.: 2001028980 

Submitted in fulfilment of the requirements in respect of the PhD degree in Human 

Movement Studies 

in the  

Department of Exercise and Sport Sciences 

in the  

Faculty of Health Sciences  

at the University of the Free State  

 

28 July 2023 

Supervisor: Prof FF Coetzee 

 

 

 



ii 

DECLARATION 

I, Arnold Vlok, declare that the PhD research thesis that I herewith submit at the 

University of the Free State, is my own independent work and has not previously 

submitted at another institution of higher education.  

I, Arnold Vlok, declare that I am aware that the copyright is vested in the University of 

the Free State.  

I, Arnold Vlok, declare that all royalties with regard to intellectual property that was 

developed during the course of and/or in connection with the study at the University of 

the Free State, will accrue to the University.  

I, Arnold Vlok, declare that I am aware that the research may only be published with 

the dean’s approval. 

 

A Vlok          30 July 2023 

I, Prof Derik Coetzee (Study Leader), approve submission of this thesis as fulfilment for 

the requirements of the PhD degree in Human Movement Science, at the University of the 

Free State. I further declare that this thesis has not been submitted as a whole or partially 

for examination purposes before.  

 
____________________  
Prof Frederik F Coetzee  

July 2023  

  

  

 



iii 

 

PRESENTATIONS ARISING FROM THE RESEARCH PROJECT 

 

Final year postgraduate student mid-year research presentations (27 June 2023) 



iv 

ARTICLES PUBLISHED FROM THE RESEARCH PROJECT 

Vlok A, van Dyk N. Coetzee D, Grindem, H. (2022). Exercise descriptors that 

determine muscle strength gains are missing from reported anterior cruciate ligament 

reconstruction rehabilitation programs: a scoping review of 117 exercises in 41 

studies. Journal of Orthopaedic Sports Physical Therapy, 52(2): 100-112.  



v 

ABSTRACT 

Introduction 
Muscle weakness after anterior cruciate ligament reconstruction (ACLR) is persistent and associated 
with abnormal biomechanics, poor knee function, new knee injury and development of osteoarthritis. 
The proposed drivers of persistent muscle weakness after ACLR are changes in muscle morphology, 
atrophy-inducing cytokines in the knee joint, and neurological alterations on a cortical and spinal level. 
The most accessible approach to target muscle weakness is various types of strength training 
exercises. However, another explanation for persistent weakness after ACLR rehabilitation could be 
that programs are not following the best practice for strength training. Failure to improve muscle strength 
after ACLR could be caused by faulty programming of exercise descriptors (e.g., exercise type, 
frequency, load). 
 
Aim 
The main aim of this study was to develop a conceptual framework to improve the reporting quality of 
strength training exercise descriptors in ACLR rehabilitation programs. 
 
Methodology  
The study was conducted in three stages, including a Scoping Review, focussing on which strength 
training exercise descriptors are reported in ACLR research after ACLR surgery, and comparing the 
current standards of reporting ACLR strength training exercise descriptors to international best practice 
strength training guidelines. The modified e-Delphi survey was utilised to formulate a conceptual 
rehabilitation framework for ACLR. The last stage included validating the preliminary ACLR conceptual 
framework that included a core outcome set (COS) of strength training exercise descriptors for reporting 
after ACLR.  
 
Results and discussion 
We extracted data on 117 exercises from 41 studies. A median of seven of the 19 possible exercise 
descriptors were reported (range 3-16). Reporting of specific exercise descriptors varied across studies 
from 93% (name of the strength training exercise) to 5% (exercise aim). On average, 46%, 35%, and 
43% of the exercise descriptors included in the ACSM, CERT, and Toigo and Boutellier guidelines were 
reported, respectively. 
 
The e-Delphi results from 27 ACLR experts regarding the 21-exercise descriptor definition was 100% 
consensus agreement (>80% agreement), also 100% consensus agreement on a COS of strength 
training exercise descriptors (). However, very low consensus agreement on exercise dosages 
prescribed in ACLR strengthening programs.   
 
The validation meeting consisted of four panellists that validated the preliminary ACLR conceptual 
framework and proposed to re-organise the 13 COS of exercise descriptors into levels of importance 
regarding the frequency of reporting. 
 
Conclusion 
The proposed ACLR conceptual framework for researchers and clinicians provided a platform for the 
reporting of strength training rehabilitation after ACLR. Improving the reporting quality of strength 
training exercise descriptors, definitions, and exercise dosages for ACLR rehabilitation programs can 
aid in the transfer of ACLR rehabilitation research towards private practice. Therefore, enabling 
clinicians to implement evidence-based strength training exercise configurations. 



vi 

ACKNOWLEDGEMENTS 

I would like to extend my sincere thanks and appreciation to the following significant 

influences in my life:  

• Firstly, to my heavenly Father, for empowering me to keep persevering within this 

storm, with all its unique challenges. Thanks for providing me with wisdom and 

understanding to solve problems for generations to come. 

• My wonderful wife, Martè, and our family, thanks for supporting me in this extended 

number of years. Martè, you are an amazing wife.  

• Appreciation to my study leader, Prof Derik Coetzee, for assisting me with putting 

this project together and providing guidance along the way.  

• To Prof Robert Schall for the statistical analysis of the scoping review and Delphi 

study and for teaching me new Excel skills that I did not know existed. 

• Words cannot express my gratitude to Dr Hege Grindem for her mentorship, 

considering the scoping review and all that I have learned about the standards of 

research. 

• Dr Nicol van Dyk, I am extremely grateful for your assistance in handling critical 

feedback from journal reviewers and for putting the Delphi steering committee 

together.  

• Special thanks to Dr Claire Arden for overviewing the Delphi study and providing 

assistance through multiple Zoom meetings. 

• I am deeply indebted to Dr Anke van de Merwe, who guided me through the last 

phase of the study and facilitated the validation meeting. 

• I had the pleasure of working with librarian Annamarie du Preez, who assisted me 

with database and article searches that I could not find. 

• I would like to thank all the ACLR rehabilitation experts who took time out of their 

busy schedules to participate in data collection. Without your valuable input, the 

research aim would not have been met. 

• Lastly, I would like to mention Jodie Teise for language editing and proofreading 

my PhD before submission. 

  



vii 

TABLE OF CONTENTS  

 

LIST OF TABLES ................................................................................................................. xiii 

LIST OF ABBREVIATIONS .................................................................................................. xvi 

DEFINITIONS.................................................................................................................... xvii 

CHAPTER 1 .......................................................................................................................... 1 

1.1 INTRODUCTION AND STUDY ORIENTATION ................................................................. 1 

1.2 RATIONAL FOR THE STUDY ........................................................................................... 1 

1.3 PROBLEM STATEMENT .................................................................................................. 4 

1.4 RESEARCH AIM .............................................................................................................. 7 

1.5 RESEARCH OBJECTIVES ................................................................................................. 7 

1.6 RESEARCH DESIGN ........................................................................................................ 8 

1.7 ETHICAL CONSIDERATIONS ........................................................................................... 8 

1.8 SIGNIFICANCE OF THE STUDY ....................................................................................... 8 

1.9 CHAPTER EXPOSITION ................................................................................................... 9 

1.9.1.  Chapter 1: Orientation to the study ................................................................. 9 

1.9.2. Chapter 2: Literature review in ACLR ............................................................. 9 

1.9.3 Chapter 3: Scoping Review .............................................................................. 9 

1.9.4 Chapter 4: Anterior Cruciate Ligament Rehabilitation: An Expert modified 

e-Delphi Perspective ....................................................................................... 10 

1.9.5 Chapter 5: A Conceptual Framework for ACLR .......................................... 10 

1.9.6 Chapter 6: Conclusions and Recommendations ........................................ 10 

CHAPTER 2 ........................................................................................................................ 12 

2.1 INTRODUCTION ........................................................................................................... 12 

2.2 ACLR EXERCISE INTERVENTIONS REQUIRE QUALITY REPORTING .............................. 13 

2.2.1 Reporting checklist for drug and general exercise interventions ............................ 13 



viii 

2.2.2 Exercise rehabilitation as a first-line treatment option for ACL injury/ACLR athletes 

  ............................................................................................................................ 14 

2.3 APPLICABILITY OF ACLR CLINICAL PRACTICE GUIDELINES (CPGS) .............................. 14 

2.4 EXERCISE TYPES AND MODES TO INCLUDE IN ACLR EXERCISE REHABILITATION 

PROGRAMS .............................................................................................................. 15 

2.4.1 Strength training (ST) vs Neuromuscular control training (NMCT): ........................ 15 

2.4.2 Close kinetic chain (CKC) vs Open kinetic chain (OKC) exercises ............................ 16 

2.4.3 Eccentric vs Concentric contractions ....................................................................... 16 

2.4.4 High-intensity vs Low-intensity ST ACLR exercises .................................................. 16 

2.5 EXERCISE DOSAGE/PRESCRIPTION OR DOSE-RESPONSE RELATIONSHIP ................... 16 

2.6 TARGETED STRENGTH TRAINING (ST) TO IMPROVE PATHOPHYSIOLOGICAL 

ALTERATIONS AFTER ACLR ...................................................................................... 17 

2.7 BEST PRACTICE STRENGTH TRAINING (ST) GUIDELINES TO REPORT ACLR ST DURING 

ACLR EXERCISE REHABILITATION PROGRAMS ........................................................ 20 

2.8 CORE OUTCOMES SET OF ACLR STRENGTHENING EXERCISE DESCRIPTORS (EDS)..... 20 

2.9 IMPROPER REPORTING OF ACLR STRENGTH TRAINING (ST) EXERCISE DESCRIPTORS 

(EDS) ........................................................................................................................ 20 

CHAPTER 3 ........................................................................................................................ 22 

3.1 INTRODUCTION ........................................................................................................... 22 

Article:  Exercise Descriptors That Determine Muscle Strength Gains Are Missing From 

Reported Anterior Cruciate Ligament Reconstruction Rehabilitation Programs: A Scoping 

Review of 117 Exercises in 41 Studies 

CHAPTER 4 ........................................................................................................................ 24 

4.1 BACKGROUND AND RATIONALE: ................................................................................ 24 

4.2 RESEARCH QUESTION ................................................................................................. 25 

4.3 RESEARCH OBJECTIVES ............................................................................................... 26 

4.4 RESEARCH METHODOLOGY ........................................................................................ 26 



ix 

4.4.1 Study design ............................................................................................................ 26 

4.4.2  Study methodology ................................................................................................. 26 

4.4.3 Overview of the modified e-Delphi study (Table 4.1 and 4.2) ................................ 27 

4.4.4 Conducting (Phase 2: Table 4.2) .............................................................................. 30 

4.4.5 Survey development ................................................................................................ 33 

4.4.5.1 Survey layout ........................................................................................................ 35 

4.4.5.2 Sample invite ........................................................................................................ 36 

4.4.5.3  Increase response rates ...................................................................................... 37 

4.3.5.4 Sample size ......................................................................................................... 37 

4.4.5.5 Pilot Study ........................................................................................................... 38 

4.5 RESULTS ...................................................................................................................... 45 

4.5.1 Delphi participants: Demographics ......................................................................... 45 

4.5.2 Response rate .......................................................................................................... 47 

4.5.3  Content analysis of the Delphi Expert Rehabilitation group survey ...................... 47 

4.5.3.1 Round 1:  ACLR exercise descriptor definitions .................................................. 47 

4.5.3.2 Amendments made following Round 1 Delphi Section 1: Definitions ............... 52 

4.5.3.3 Round 2: ACLR exercise descriptor definitions ................................................... 52 

4.5.4: Section 2: Core Outcome Strength Training (COS) checklist of ACLR Strength 

Training (ST) Exercise Descriptors (EDs) .................................................................. 55 

4.5.4.1: Round 1: Core outcomes set of ACLR ST EDs ...................................................... 55 

4.5.4.2 Round 2:  COS strength exercise training descriptor consensus ........................ 59 

4.5.5 Exercise dosages prescribed during ACLR rehabilitation ........................................ 59 

4.6 DISCUSSION OF RESULTS ............................................................................................ 67 

4.6.1 Strength training definitions to be used in ACLR rehabilitation programs ............. 67 

4.6.2 ACLR core outcomes set (COS) of ST EDs ................................................................ 69 



x 

4.6.3 Exercise dosages proposed by the Anterior Cruciate Ligament Reconstruction 

Expert Rehabilitation Group (ACLR ERG) ................................................................ 71 

4.6.3.1 Repetition prescribed (Table 4.11 & 4.12) ......................................................... 71 

4.6.3.2 % RM prescribed (Table 4.11 & 4.12) ................................................................. 74 

4.6.3.3 Rest between sets prescribe (Table 4.11 & 4.12) ............................................... 75 

4.6.3.4 Sessions per week prescribe (Table 11&12) ....................................................... 75 

4.6.4 Exercise dosages proposed by ACSM, T&B and CERT as well as comparison with 

ACL ERG (Table 13) .................................................................................................. 76 

4.6.4.1 Strength Endurance focus .................................................................................. 78 

4.6.4.2 Strength/hypertrophy focus: .............................................................................. 81 

4.6.4.3 Maximum strength focus:................................................................................... 85 

4.6.4.4 Rate of force development (RFD) focus: ............................................................ 87 

4.6.5 The lack of consensus agreement on exercise dosage in ACLR rehabilitation 

programs ................................................................................................................. 91 

4.6.6 Strength and Limitations of the study ..................................................................... 93 

4.6.7 Conclusion and Recommendations for future research ......................................... 94 

References List: (Table 4.13) ............................................................................................. 95 

CHAPTER 5 ........................................................................................................................ 99 

5.1INTRODUCTION ............................................................................................................ 99 

5.2 RESEARCH QUESTION ............................................................................................... 100 

5.3 OBJECTIVES OF THE FOURTH PHASE ........................................................................ 100 

5.4 RESEARCH METHODOLOGY ...................................................................................... 101 

5.4.1 Study design ........................................................................................................... 101 

5.4.2 Study methodology ................................................................................................ 101 

5.4.2.1 Target population ............................................................................................... 101 

5.4.2.2 Validation panel expert setting ........................................................................ 102 



xi 

5.4.3 Unit of analysis ....................................................................................................... 103 

5.5 Exploratory study ...................................................................................................... 105 

5.6 Data collection and construction process ................................................................ 107 

5.7 Content Analysis ....................................................................................................... 109 

5.8 Content Analysis ....................................................................................................... 111 

5.9 RESULTS AND DISCUSSION ....................................................................................... 111 

5.9.1 Theme 1: Evidence of reporting exercise dosages ........................................... 111 

5.9.2 Theme 2: Neuromuscular adaptational responses .......................................... 114 

5.9.3 Theme 3: Evidence base considerations .......................................................... 118 

5.9.4 Theme 4: Contextual factors ............................................................................ 121 

5.9.5 Theme 5: Reporting framework ....................................................................... 125 

5.9.7 Conclusion......................................................................................................... 131 

5.9.7.1 ACLR conceptual framework finalisation ......................................................... 133 

5.9.7.2 Application of the ACLR conceptual framework .............................................. 135 

5.9.7.3 Clinical status of the knee joint assessment1 and ACLR strengthening program2 

  .......................................................................................................................... 135 

5.9.7.4 Repetition maximum (RM) continuum practice in ACLR strength training (ST) 

programs ......................................................................................................................... 135 

5.9.7.5 Different exercise modes .................................................................................... 136 

5.9.7.6 Capturing exercise dosages ............................................................................. 138 

5.9.7.7 Target pathophysiological alterations after ACLR surgery .............................. 138 

5.9.7.8 No “one size fits all” ACLR exercise prescription ............................................. 139 

5.9.8 Limitations ........................................................................................................ 140 

5.9.10 Conclusion......................................................................................................... 141 

CHAPTER 6 ...................................................................................................................... 142 



xii 

6.1Introduction ............................................................................................................... 142 

6.2 ACLR conceptual framework development and finalisation .................................... 142 

6.3 Recommendations .................................................................................................... 144 

6.4 Contribution .............................................................................................................. 144 

REFERENCES .................................................................................................................... 145 

APPENDIX A: Approval letter from Health Sciences Research Ethics Committee (UFS) 175 

APPENDIX B:  Preferred Reporting Items for Systematic reviews and Meta-Analyses 

extension for Scoping Reviews (PRISMA-ScR) Checklist ................................................. 176 

APPENDIX C: Boolean phrase to search the databases .................................................. 178 

APPENDIX D: Articles excluded with reasons Boolean ................................................... 179 

APPENDIX E: Delphi participants' information sheet ..................................................... 183 

APPENDIX F: Validation of participant information ........................................................ 187 

APPENDIX G: Preliminary draft of ACLR conceptual framework for validation ............. 190 

APPENDIX H: Interview sheet questions......................................................................... 196 

 



xiii 

LIST OF TABLES 

Table 4.1: Designing an e-Delphi using CREDES (Jünger et al., 2017: 684) ........... 26 

Table 4.2: Overview of the Delphi process (Adapted with changes from Beiderbeck et 

al., 2021) .................................................................................................................. 30 

Table 4.3: Steps in selecting the panel of experts (Gill et al., 2013: 1324) ............... 33 

Table 4.4: Summary of data analysis between Rounds 1-3 ..................................... 43 

Table 4.5: Demographics of the ACLR Expert Rehabilitation Group recruited for the 

modified e-Delphi survey .......................................................................................... 46 

Table 4.6: Response rate between different rounds and different sections of the survey

 ................................................................................................................................. 47 

Table 4.7: ACLR exercise descriptor definitions that achieved consensus/no 

consensus after Round 1 survey .............................................................................. 49 

Table 4.8: Included ACLR exercise descriptor consensus definitions after Round 2 53 

Table 4.9: Core outcomes set of ACLR strength training exercise descriptor that 

achieved consensus/no consensus after Round 1 ................................................... 56 

Table 4.10: Core outcomes set of ACLR strength training exercise descriptor that 

achieved consensus after Round 2 .......................................................................... 58 

Table 4.11: Exercise dosage configurations which achieved consensus during Round 

1 (Repetitions prescribed) ........................................................................................ 60 

Table 4.12: Exercise dosage configurations which achieved no consensus from 

Rounds 2-3 (ACLR ST exercises prescribed per session) ....................................... 62 

Table 4.13: Strength training exercise recommendation for ACLR rehabilitation 

according to modified Delphi and best practice guidelines ....................................... 72 

Table 5 1: Demographics of validation meeting panellists ...................................... 104 

Table 5.2: Questionnaire changes after exploratory study ..................................... 106 



xiv 

Table 5.3: Content analysis summery following validation meeting ....................... 109 

Table 5.4: Strength training exercise descriptors comparison with other intervention 

reporting frameworks .............................................................................................. 132 

Table 5.5: ACLR Worksheet ................................................................................... 137 

 



xv 

LIST OF FIGURES 

Figure 1.1: The problem regarding strength training (ST) exercise descriptors (EDs) in 

ACLR .......................................................................................................................... 6 

Figure 1.2: Summary of the study process ............................................................... 11 

Figure 2.1: Reporting of the exercise descriptors (EDs) that drive molecular 

adaptational responses (developed by the researcher and adapted from Thomson et 

al., 2015) .................................................................................................................. 18 

Figure 2.2: Repetition maximum (RM) continuum (Beachle & Earl, 2008) ............... 19 

Figure 4.1: Workflow of the modified e-Delphi study process ................................... 29 

Figure 4.2: Example of 9-point Likert scale used during Round 1 ............................ 34 

Figure 4.3: Example of ACLR exercise dosage survey layout .................................. 35 

Figure 4.4: Section 3: Round 1 survey with 5 options to select from ........................ 61 

Figure 4.5: Section 3: Round 2 and 3 surveys with three options to select from ...... 61 

Figure 5.1: Classifying of validation panel .............................................................. 102 

Figure 5.2: Target ACLR strengthening exercises to improve quadriceps and 

hamstring weakness Compiled by the researcher, Vlok, 2023, as part of thesis .... 115 

Figure 5.3: COS-1 exercise descriptors that should be reported within each ACLR 

exercise rehabilitation session ............................................................................... 127 

Figure 5.4: COS-2 exercise descriptors that should be reported once ................... 127 

Figure 5.5: COS-3 exercise descriptors that should be reported when deviated from 

the norm ................................................................................................................. 128 

Figure 5.6: Final ACLR Conceptual Framework to improve the reporting of strength 

training exercise descriptors in ACLR exercise rehabilitation programs ................. 134 

Figure 5.7: Strength training exercise configurations drive neurophysiological 

responses after ACLR surgery ............................................................................... 139 



xvi 

LIST OF ABBREVIATIONS 

 

Abbreviation Meaning 

Anterior cruciate ligament ACL 

Anterior cruciate ligament expert rehabilitation group ACLR ERG 

Anterior cruciate ligament reconstruction ACLR 

Arthrogenic muscle inhibition AMI 

American College of Sports Medicine ACSM 

Centre for Reviews and Dissemination  CRD 

Clinical practice guidelines CPGs 

Close kinetic chain CKC 

Consensus on Exercise Reporting Template CERT 

Core outcome set COS 

Exercise descriptors EDs 

Neuromuscular control training NMCT 

Open kinetic chain OKC 

PRISMA Extension for Scoping Reviews PRISMA-ScR 

Randomised controlled trial  RCT 

Repetition maximum RM 

Return to sport RTS 

Strength training ST 

Template for Intervention Description and Replication TIDieR 

 

  



xvii 

DEFINITIONS  

Conceptual Framework: A conceptual framework refers to a “researcher’s 

constructed model, which explains interconnected vital 

concepts and relationships exploring the research 

problem. Conceptual frameworks are commonly seen in 

qualitative research in the social and behavioural sciences, 

for example, because often one theory cannot fully 

address the phenomena being studied” (Adom et al., 2018: 

438). 

    

Exercise Descriptors (EDs): Toigo and Boutellier, (2006) outline important 

mechanobiological exercise descriptors, which 

provide a framework to standardise the design and 

description of resistance exercise investigations. 

Examples of some descriptors 1) Repetitions; 2) 

Sets; 3) Load magnitude; 4) Rest between 

Repetitions; 5) Frequency of sessions (Toigo & 

Boutellier, 2006). 

Strength Training (ST): Strength training was defined by Zatsiorsky et al., (2020), 

as the practice of a certain exercise modality to improve 

the body's ability to overcome or counteract external 

resistance by specific muscular effort (concentric, 

eccentric, or isometric muscular contractions). Include the 

repetition maximum continuum from strength endurance 

focused to power / rate of force development focused. 

  



 

 

1 

CHAPTER 1 

 

INTRODUCTION 

_________________________________________________________________ 

1.1 INTRODUCTION AND STUDY ORIENTATION   

Chapter 1 will postulate the problem statement, rationale, research question, aim, 

research objectives, research design, ethical considerations, significance of the study 

and the chapter exposition. 

 

This PhD study was planned and implemented as a single report but is presented in 

the form of chapters and an article, which includes background or additional 

information to the research. The research approach serves to combine the chapters 

and article into a cohesive entity.  

 

It is important to note that the article should be interpreted as an independent entity 

with some connections and consequent overlap. This orientation to the study 

functions as an introduction to the research and intends to provide the reader with a 

holistic view of the study. The target market were researchers and clinicians working 

with patients after anterior cruciate ligament reconstruction (ACLR). 

1.2 RATIONAL FOR THE STUDY   

"When can I play again?" is the most frequently, emotionally charged, typical question 

asked by almost every athlete after an anterior cruciate ligament (ACL) injury. 

Invariably, the same question is also one of the first asked by teammates, parents, 

coaches, and, in the case of high-profile athletes, the media. This implies that swift 

surgical intervention is often selected to meet these expectations, and accelerated 

rehabilitation becomes a priority (Myklebust & Bahr, 2005). However, the criteria to 

determine a return to sport (RTS) readiness remain arbitrary, as does the optimal 

ACLR strength training (ST) program (Glattke et al., 2022).  

 

There may be underlying reasons why clinicians use different approaches to prepare 

the athlete for RTS participation. A possibility could be the poor reporting of 



 

 

2 

resistance training programs that prevent accurate translation and implementation in 

clinical practice, considering that up to 40% of physiotherapists indicated that original 

research and articles were the preferred resource to learn from when treating patients 

with musculoskeletal pain (Holden et al., 2019; Barton et al., 2021). Secondly, 

physiotherapists lacked the ability to prescribe ST exercises for people with 

musculoskeletal pain. This is according to an international survey of 1,352 

physiotherapists from 56 countries. Only 16% could identify an accepted ST best 

practice guideline, such as that of the American College of Sports Medicine (ACSM) 

guidelines (Barton et al., 2021). Although this is a problem, it is not clear if it persists 

in ACLR. 

 

Research efforts have been non-specific about the reporting, the detail of the ST 

exercise descriptors (EDs) in ACLR rehabilitation programs, and inadequate 

reporting of the resistance training intensity of these rehabilitation programs (Goff et 

al., 2016; Augustsson, 2013; Nichols et al., 2021). Consequently, there is little 

information available on the dose-response relationship between the volume and/or 

intensity of ST exercise and outcomes and what constitutes the optimal rehabilitation 

strategy to return patients to their preinjury level of sport and prevent reinjuries 

(Kotsifaki et al., 2023). 

 

Webster and Feller (2019;578) recently determined "that patients who were about to 

undergo a primary ACLR had high expectations for their return to preinjury level of 

sport, with 88% expecting to achieve this outcome". Ardern et al. (2011) agrees and 

mention that only 65% of patients after ACLR return to their preinjury level of sport. 

Reinjury rates can be as high as 25% (Wiggins et al., 2016), and only 33% of injured 

athletes return to competitive sports after 12 months of ACLR surgery (Ardern et al., 

2011). It is concerning that only 5% of ACLR athletes were managed using ACLR 

evidence-based guidelines (Ebert et al., 2017). Considering these facts, a feasible 

first line-treatment model that can navigate the optimal final ACLR outcomes remains 

debated.  

 

Anterior cruciate ligament reconstruction is considered by many as the clinical 

standard to restore the mechanical stability of the joint as a prerequisite for RTS 



 

 

3 

participation (Gokeler et al., 2022). Conflicting evidence challenges the golden 

standard of ACLR surgery with exercise compared to exercise and optional delayed 

ACLR in 121 patients participating in the KANON trial (Frobel et al., 2010). An 11-

year follow-up of the KANON trial indicates no superior improvement in the KOOS4 

(pain, symptoms, function in sports and recreation, knee-related quality of life) 

outcomes when ACLR surgery with exercise was compared to exercise and optional 

delayed ACLR surgery (Lohmander & Roemer et al., 2023). In a secondary analysis 

of the KANON trial, research indicates evidence of ACLR healing on MRI following 

ACL rupture treated with rehabilitation. Healing responses occur in 30% of patients 

treated within the ACLR ruptured rehabilitation group (Filbay et al., 2023). 

 

Other evidence, the COMPARE randomised control trial, which used the same 

objectives as the KANON trial, indicated superior knee function and ability to 

participate in sports after two years (Reijman et al., 2021). Some consideration that 

should be highlighted in the COMPARE trial was that 50% of patients randomised to 

the rehabilitation group opted for no ACLR surgery (Reijman et al., 2021).  

 

Essentially, ACLR rehabilitation should be considered as important as any golden 

standard treatment for ACL injury as a standalone treatment or in combination with 

surgery to prepare patients for successful sports participation. Therefore, the 

standard of rehabilitation considering the intensity, frequency, compliance, and 

reproducibility of a training protocol is of significance when examining the evidence 

and translating it into clinical practice for ST following ACL injury or reconstruction 

(Page et al., 2016; Filbay, 2022).  

 

Anterior cruciate strengthening programs form the cornerstone of targeting muscle 

weakness in collaboration with other modalities like neuromuscular/motor control 

training to prepare athletes for their pre-injury levels of play after surgery (Risberg et 

al., 2007; Andrade et al., 2019; Kotsifaki et al., 2023). Contradicting the expected 

positive effect of ST on muscle weakness, it is evident throughout the research that 

strength and power deficits persist after completing an ACLR-standardised ST 

rehabilitation program (Tayfur et al., 2020). Arthrogenic muscle inhibition, and  



 

 

4 

psychological factors can be some reasons for this continuous muscle insufficiencies 

(Beischer et al., 2019; McPherson et al., 2023). Nevertheless, reporting and 

implementing effective evidence-based ST exercises targeting neuromuscular 

strength deficits should be every clinician and researcher's responsibility. 

A lack of proper reporting of ACLR EDs that determine muscle gains makes it 

impossible to replicate the exercise intervention with its results in clinical practice 

(Page et al., 2017; Goff et al., 2018; Poretti et al., 2023). Therefore, absent EDs may 

leave clinicians and other researchers with the likelihood to interpolate with their own 

ST considerations. Consequently, the altered performance of ACLR ST programs 

could lead to a wide variation in individuals' physiological responses and overall 

clinical outcomes. A gap in the research emerges considering the reporting of ST 

EDs in ACLR rehabilitation programs targeting muscle weakness.  

 

Therefore, an ACLR conceptual framework is needed to improve the quality of 

reporting ST EDs after ACLR surgery. Such an ACLR conceptual framework will 

hopefully enable researchers and clinicians to effectively micro-manage the individual 

EDs and progressions within the ACLR rehabilitation program. The primary reason 

for this focused approach is to target musculoskeletal strength deficits that develop 

after ACLR surgery. 

 

1.3     PROBLEM STATEMENT 

Anterior cruciate ligament reconstruction (ACLR) rehabilitation literature indicated 

poor reporting of strength training (ST) exercise descriptors (EDs) for research 

purposes (Augustsson et al., 2013). Such a problem is not unique to the ACLR 

rehabilitation field. It similarly affects the implementation of rehabilitation for other 

musculoskeletal conditions, like patellofemoral pain syndrome and achilles tendon 

ruptures (Holden et al., 2018; Christensen et al., 2020).   

 

Level 1 evidence indicated that the majority (9/11) ACLR rehabilitation studies (Vlok 

et al., 2022) lack adequate reporting of resistance training intensity to meet the 

demands of RTS after ACLR surgery (Nichols et al., 2021). Consequently, the 

question remains if ACLR patients were fully prepared to manage the higher 



 

 

5 

demands of power and strength components related to ST rehabilitation. However, 

no evidence existed regarding the possible reinjury risk of this matter. 

 

Culvenor et al., 2022, concluded in a recent systematic review with 142 randomised 

control trials low evidence for ACLR rehabilitation's effectiveness, including 

interventions like neuromuscular control exercises and open and close kinetic chain 

(CKC) exercises to improve symptomatic and functional outcomes. Opposingly, 

clinical guidelines proposed strength training, including isotonic and isokinetic, 

concentric, and eccentric training, as a cornerstone for the treatment of ACLR 

patients (Van Melick et al., 2016; Kotsifaki et al., 2023). Therefore, the rehabilitation 

of the ACLR patient should follow the clinical practice guidelines (CPGs) proposed 

for ACLR patients to enable them to return to their pre-injury preferred activity to 

prevent post-traumatic knee osteoarthritis (Van Melick et al., 2016; Whittaker et al., 

2022).  

 

In the systematic review, Andrade et al. (2020:512) ask, "How should clinicians 

rehabilitate patients after ACL reconstruction?" The emphasis of the review was on 

CPG with a focus on quality appraisal. Conclusions showed that applicability, "the 

ease with which clinicians can implement the CPG recommendations into clinical 

daily practice", was rated very poorly. Reasons for that are outside the scope of this 

study, but, importantly, clinicians find it difficult to implement best practice evidence-

based ACLR guidelines. 

 

Considering evidence-based practice and the implementation into clinical practice, 

the OPTIKNEE group indicated that the ACLR exercise intervention should be 

documented by utilising the Consensus on Exercise Reporting Template (CERT), a 

platform developed specifically for exercise trials by Slade et al. (2016) (Culvenor et 

al., 2022). No research evaluated the inclusion of the CERT platform into ACLR 

rehabilitation until 2020. However, some earlier evidence indicates a low uptake of 

ST EDs included in tibiofemoral joint soft tissue injuries programs (Goff et al., 2018).  

 



 

 

6 

Despite the perceived value of exercise rehabilitation following ACLR, some 

challenges exist. However, there is no clear consensus concerning specific exercise 

dosages or which ST EDs should be documented within ACLR strengthening 

programs (Augustsson, 2013; Culvenor et al., 2022).  

 

The researcher perceived the current research problem concerning ST EDs in Figure 

1. An ACLR patient enters ACLR rehabilitation with the focus on being prepared for 

desired pre-injury levels of play. When conducting strength training, it is essential to 

know which ACLR ST EDs (repetitions, sets, load magnitude, frequency of sessions, 

etc.) were prescribed during clinical trials to replicate in clinical practice expecting the 

same results (Page et al., 2017).  

 

 

 

Figure 1.1: The problem regarding strength training (ST) exercise descriptors (EDs) in ACLR 

 

The general problem was that no research exists concerning which EDs are used in 

rehabilitation after ACLR, and secondly, how did the literature compare to 

international standards of reporting strength training? A conceptual framework design 

was adopted to answer the research question considering the importance of such 

difficulty when ST encompasses an important component of rehabilitating ACLR 

patients (Van Melick et al., 2016; Andrade et al., 2019). 

 

Several conceptual frameworks can be used to facilitate the implementation process 

and record increased instances of practice change and the spread of evidence 

(Alatawi, 2019). Casanave and Li (2015) and Parahoo (2006) distinguish between a 

theoretical framework and a conceptual framework as follows: “a theoretical 

framework is a specific framework or theory that underpins a research study, while a 

conceptual framework draws on various theories, frameworks, and findings to guide 

the research”. Maxwell (2005:52) concluded and defined “the conceptual framework 

of a study as a system of concepts, assumptions, expectations, beliefs, and theories 

that supports and informs the research". The conceptual framework, in essence, 

ACLR  patient  

 
ACLR ST exercise descriptors 

prescribed during 
rehabilitation 

???? 

ACLR patient 

participating in sport 

activity 



 

 

7 

describes the key factors, concepts and variables and the relationship between them. 

It can be regarded as the plan or model of what the researcher intends to design. 

Based on the lack of current evidence concerning which EDs should be included in 

an ACLR ST program, it was advisable to use a conceptual framework design to 

include different notions, traditions, and views from different stakeholders when 

performing ACLR strength training. 

For that reason, our research question was: What ACLR framework exists for 

researchers and clinicians to improve the report quality regarding the specificity of 

ST EDs utilised while conducting ACLR rehabilitation?  

 

1.4 RESEARCH AIM 

The aim of this study was to develop an ACLR rehabilitation injury management 

conceptual framework for clinicians and researchers working with athletes after 

ACLR. While considering the aim of the study, the following research objectives were 

formulated in point 1.5. 

1.5 RESEARCH OBJECTIVES 

The objectives of this study were: 

Objective 1: Review the literature to 1) determine which strength training (ST) 

exercise descriptors (EDs) are used in rehabilitation after ACLR 

surgery and 2) how the literature compares to international standards 

of reporting ST EDs in ACLR rehabilitation programs. 

Objective 2: Develop a consensus set of ACLR ST EDs as outcomes.  

Objective 3: Validate the preliminary ACLR conceptual framework through four 

national and international subject, clinical and framework experts.  

Objective 4: Finalise the ACLR conceptual framework that includes the COS ST 

EDs for reporting after ACLR.  

 

The above-mentioned objectives were achieved during the four study phases, 

namely (Figure 1.2): 

Phase 1:  Scoping review of literature on ACLR rehabilitation. 



 

 

8 

Phase 2:  Modified e-Delphi survey amongst International and South African experts 

regarding exercise prescription descriptors and criteria for progression. 

Phase 3: Validation process and the development of a conceptual framework for 

ACLR rehabilitation. 

Phase 4: Finalisation of the ACLR conceptual framework.  

 

1.6 RESEARCH DESIGN 

A quantitative and qualitative research approach was followed to achieve the purpose 

and objectives of the study. A mix-method research approach was needed to collect 

and analyse all the relevant data for this study. The mixed-method approach enables 

us to "intensify and deepen the understanding and validation of the rich data collected 

in the study" (Almalki, 2016:291). Details regarding the specific research methods, 

study participants, measuring instruments and data capturing applied to answer each 

research objective will be included in chapters 3 to 5. 

 

1.7 ETHICAL CONSIDERATIONS  

The research protocol was presented to the Health Sciences Research and Ethical 

Committee (HSREC) at the University of the Free State (UFS) for approval. Ethical 

clearance (HSREC: UFS-HSD2019/1889/2502) was obtained before the 

commencement of the study. Any changes during the progress of finalising the study 

were approved as amendments to the protocol by the same committee (refer to 

Appendix A). 

 

1.8 SIGNIFICANCE OF THE STUDY 

The value of this study will provide researchers and clinicians with one common 

ACLR framework to report and implement strength training (ST) exercise descriptors 

(EDs) while conducting ACLR rehabilitation. Secondly, ACLR exercise intervention 

utilised during clinical trials can be directly translated to clinical practice, replicating 

evidence-based research results. Lastly, the ACLR framework could set the stage for 

further research to build on solid findings. 

 



 

 

9 

1.9 CHAPTER EXPOSITION 

This thesis consists of an introductory chapter (Chapter 1), followed by five main 

chapters comprising a literature review (Chapter 2), followed by a scoping review 

(Chapter 3), the modified e-Delphi on the COS of strength training (ST) exercise 

descriptors (EDs) (Chapter 4). The following chapter concludes the validation and 

finalisation of the conceptual framework for ACLR rehabilitation (Chapter 5) (See 

Figure 2). The concluding chapter (Chapter 6) includes the strengths, weaknesses, 

and recommendations for further studies. The six chapters are: 

 

1.9.1.  Chapter 1: Orientation to the study  

The first chapter provides a brief background on ACLR, serving as an introduction to 

the study. The aim was to highlight the main purpose and objectives of the study as 

well as the layout of the thesis.  

1.9.2. Chapter 2: Literature review in ACLR 

This chapter intended to give a knowledge overview of the key literature relevant to 

ACLR rehabilitation as first-line treatment, clinical best practice guidelines for ACLR 

rehabilitation, current reporting of ACLR EDs and targeted ST for ACLR patients. 

Research gaps open concerning the reporting of ST in ACLR rehabilitation programs. 

This review provides a strong foundation for the ACLR conceptual framework and 

confirms the methodology used for this research project. 

1.9.3 Chapter 3: Scoping Review 

To identify and analyse knowledge gaps concerning the reporting of ACLR ST EDs 

utilised in Level 1-4 studies, a scoping review (DOI: 

https://doi.org/10.2519/jospt.2022.10651) was conducted. The aim of this scoping 

review was to explore the extent of the literature and to map and summarise the 

evidence in view of the following two objectives: 

1. Describe which ST EDs were reported in ACLR rehabilitation research.  

2. Compare the current standards of reporting ACLR ST EDs to international best-

practice ST guidelines. 

 



 

 

10 

This scoping review (Vlok et al., 2022) informs the following stage in the thesis, 

specifically the conduction of a modified e-Delphi considering the list of ACLR EDs 

utilised in the conclusion of the scoping review (Table 1). 

 

1.9.4 Chapter 4: Anterior Cruciate Ligament Rehabilitation: An Expert modified e-

Delphi Perspective 

The purpose of this section of the research study was related to Objective 2 utilising 

a modified e-Delphi survey as a unique approach to formulate a rehabilitation 

framework for ACLR. The evidence obtained in Chapter 3 laid the foundation for the 

construction of the e-Delphi survey and served as a relevant connection and overlap 

between current evidence and the development of a new COS of ST EDs. This was 

accomplished by collecting qualitative opinions, supplemented with some 

quantitative elements, from twenty-seven (27) ACLR experts representing 

International and South African views on ACLR ST exercise programs. The results 

and subsequent discussion of these results are presented. 

 

1.9.5 Chapter 5: A Conceptual Framework for ACLR  

Chapter 5 concluded the formal validation of the new framework for ACL rehabilitation 

by experts. Therefore, this chapter serves as the overall summary of the findings of 

the study in the form of a conceptual framework for ACLR rehabilitation. The purpose 

of this study was to formulate a conceptual framework to improve the reporting of ST 

EDs within ACLR rehabilitation programs utilising both quantitative and qualitative 

methods of data collection. Data were processed and interpreted for the scoping 

review as well as the e-Delphi questionnaire and will be presented collectively to 

describe how the outcomes of the study were achieved. 

 

1.9.6 Chapter 6: Conclusions and Recommendations 

A holistic view of the research project as a single entity is provided in this chapter, 

including recommendations and other considerations regarding the strengths and 

limitations of the study. 



 

 

11 

 

Figure 1.2: Summary of the study process 

  

 

 Preparation 

 
Pre-liminary reading and conceptualisation of the research domain, research 
question and research aims. 

  Finalisation of the research proposal and approval of the study. 

 

 

Phase 1 
 Scoping review 

 
Data search and analysis. 
Completion of the scoping review. 
Preparation of research output (article) regarding scoping review completed. 

 
Phase 2  

Modified e-Delphi 
study 

 

  
   Compilation of modified e-Delphi survey and panel of national/ international ACLR 

experts. 
   Created ACLR expert rehabilitation group (ACLR_ERG) as the panel that 

completed three rounds of the survey. 

 

 
Phase 3 

Preliminary ACLR 
conceptual  
framework 

  

 
Prepare a preliminary hypothetical ACLR conceptual framework for validation 
purposes. 

 Phase 4  
Finalisation 

 

Formal validating of the hypothetical conceptual framework for ACLR ST 
programs. 
Finalisation of research thesis/research outputs. 
Presentation of thesis/research outputs for examination. 



 

 

12 

CHAPTER 2 

 

LITERATURE OVERVIEW 

_________________________________________________________________ 

2.1 INTRODUCTION 

Proper reporting of the strength training (ST) exercise descriptors (EDs) (repetitions, 

sets, interset rest, tempo etc.) utilised during ACLR exercise rehabilitation programs 

is a fundamental consideration to replicate evidence-based results (Page, 2017; Goff 

et al., 2018; Nicolas et al., 2021). Unfortunately, an evidence gap exists regarding the 

reporting standards for ACLR ST EDs while conducting exercise rehabilitation 

(Augustsson, 2013). Considering the importance of exercise rehabilitation as first-line 

treatment, emerging Level 1 evidence compares the 11-year effect of exercise 

rehabilitation plus early ACLR with exercise rehabilitation plus optional delayed ACLR 

(when instability persists). Outcomes indicated no superior effect for surgery above 

exercise rehabilitation when compared with each other (Saueressig et al., 2022; 

Lohmander & Roemer, 2023). Confirming the importance of ACLR and exercise 

rehabilitation or ACL injury in addition to rehabilitation, exercise rehabilitation can be 

considered as a central theme for treatment. Therefore, increasing reporting 

standards of the ST EDs utilised during exercise rehabilitation enables the end-user 

(researcher and clinicians) to replicate ACLR evidence-based programs (Slade et al., 

2016; Page et al., 2017).  

 

This chapter is structured as follows: In the literature review, current reporting 

platforms for exercise clinical trials and the applicability of ACLR clinical practice 

guidelines (CPGs) were discussed to present a logical flow of ideas. Best practice 

rehabilitation guidelines enable clinicians to distinguish between certain kinds of 

exercises and modes of training, which were debated concluding the literature review 

by reporting the necessity of exercise dosages and replicating target ST EDs for 

ACLR pathophysiological alterations. 

 



 

 

13 

2.2 ACLR EXERCISE INTERVENTIONS REQUIRE QUALITY REPORTING   

The evaluation of an intervention during a clinical trial is often the primary objective 

of a study. Therefore, the quality of the intervention description is very important. 

When the trial report becomes available through journal publications, a poor 

description will mean that others may find the intervention difficult to implement in 

clinical work or replicate for research (Bandholm et al., 2017). Considering that ACLR 

ST exercise interventions are poorly documented (Augustsson, 2013; Vlok et al., 

2022), it could be challenging for practitioners to implement ACLR evidence-based 

exercise rehabilitation programs for the lack of reporting essential exercise 

descriptors (EDs). Current evidence indicates the potential advantage of ACLR 

exercise rehabilitation as first-line treatment compared to surgical interventions for 

ACL-injured patients or best practice recommendations after ACLR (Reijman et al., 

2021; Kotsifaki et al., 2023). As a result, ACLR exercise rehabilitation interventions 

should be reported in evidence-based reporting checklists.  

 

2.2.1 Reporting checklist for drug and general exercise interventions 

According to Hoffman et al. (2016: 348) "without a complete published description of 

the intervention, clinicians and patients cannot reliably implement interventions that 

are shown to be useful, and other researchers cannot replicate or build on research 

findings". Considering this, Slade et al. (2016) developed the Consensus on Exercise 

Reporting Template (CERT), which consists of 16 checklist elements to include in 

exercise intervention reporting. Only items 7a, 7b (progressions of exercises and 

program), and 13 (reporting of repetitions, sets, and resistance load) indicated the 

reporting of ST EDs utilised during clinical trials. Other generic reporting guidelines 

also exist. The Template for Intervention Description and Replication (TIDieR) exists 

to improve reporting of drug interventions in general and not specific to exercise 

interventions (Hoffman et al., 2014). Both of these reporting checklists were not 

specifically developed to capture the required details of EDs used during ACLR 

clinical trials, but evidence should direct us towards the importance of exercise 

rehabilitation as a treatment for ACLR surgery.  

 



 

 

14 

2.2.2 Exercise rehabilitation as a first-line treatment option for ACL 

injury/ACLR athletes 

As the literature presented here indicates that ACLR surgery should be an option to 

consider after an ACL injury (Rodriguez et al., 2021; Reijman et al., 2021). Following 

ACLR, surgery is no longer mandatory because of the potential long-term benefits 

(decrease in knee osteoarthritis) compared to other comparator treatments like 

exercise rehabilitation. Fifty percent (50%) of ACL-injured individuals will develop 

symptomatic osteoarthritis within ten years, regardless of operative or non-operative 

treatment (Poulsen et al., 2019). “The three key treatment options for an ACL rupture 

are: 

1. rehabilitation as first-line treatment (followed by ACLR) in patients who develop 

functional instability,  

2. ACLR and postoperative rehabilitation as the first-line treatment, and  

3. preoperative rehabilitation followed by ACLR and postoperative rehabilitation” 

(Filbay et al., 2019; Whittaker et al., 2022). 

 

Highlighting the significance of exercise rehabilitation programs that serve as first-

line treatment options for ACL injured/ACLR patients, clinicians should prescribe 

ACLR exercise training from well-reported best practice guidelines (Andrade et al., 

2019; Van Melick et al., 2016; Kotsifaki et al., 2023).  

 

2.3 APPLICABILITY OF ACLR CLINICAL PRACTICE GUIDELINES (CPGS) 

How should clinicians rehabilitate patients after ACLR? Level 1 evidence suggests 

that CPGs should be followed to improve ACLR patient outcomes during and after 

rehabilitation (Van Melick et al., 2016; Andrade et al., 2020).) Therefore, quality ACLR 

research must be translated and implemented in clinical practice. Unfortunately, 

according to Andrade et al. (2020), the applicability (the ease with which clinicians 

can implement the CPGs recommendations into daily clinical practice) domain of six 

different CPGs rated according to the AGREE II assessment tool is 29%. The reasons 

for this low applicability level were outside the study's scope. Still, the quality of 

reporting the ACLR exercise interventions utilised during clinical trials is a possible 

further obstacle in the pathway of clinical uptake and applicability that should be 



 

 

15 

investigated (Augustsson, 2015; Goff et al., 2018). Sixty-six percent (66%) of the 

international CPGs for rehabilitation after ACLR recommended different exercise 

types and modes of exercise training to be included in clinical practice, considering 

its effectiveness in targeting neuromuscular alterations (Welling et al., 2019: Andrade 

et al., 2020). 

 

2.4 EXERCISE TYPES AND MODES TO INCLUDE IN ACLR EXERCISE 

REHABILITATION PROGRAMS 

2.4.1 Strength training (ST) vs Neuromuscular control training (NMCT): 

Both these exercise types need to be incorporated into ACLR exercise rehabilitation 

programs (Risberg et al., 2007; Van Melick et al., 2016). The final goal of an ACLR 

strengthening program is to target muscle weakness, restoring muscle strength and 

power needed for participation in the patient's sport and desired recreational 

activities, while the final goal of any NMCT program is to restore dynamic postural 

control which may be lacking after ACLR (Filbay et al., 2019; Paterno et al., 2010).  

 

Contrary to previous evidence, current Level 1 evidence indicates no advantage to 

knee functionality in doing neuromuscular control rehabilitation exercises following 

the ACLR when compared with a traditional strengthening program (Cooper et al., 

2005; Bakowski et al., 2023). Additionally, four systematic reviews identified the 

heterogeneity in studies utilised for the neuromuscular control intervention used, the 

test conducted to measure the variable. There is not enough scientific evidence to 

substantiate the inclusion of NMCT exercises or the effectiveness 6-24 months after 

ACLR (Costa et al., 2020; Arumugam et al., 2021; Ma et al., 2021; Fleming et al., 

2022).  

 

Consequently, the inclusion of the reporting of NMCT programs in our study was not 

validated. As a result, the main objective of our study was to consider reporting the 

ST exercise descriptors (EDs) utilised to improve knee functionality after ACLR 

surgery and, therefore, include different modes of strength training.  

 



 

 

16 

2.4.2 Close kinetic chain (CKC) vs Open kinetic chain (OKC) exercises 

Clinical practice guidelines (CPGs) proposed that ST can be implemented 

immediately after ACLR, starting with CKC exercises, followed by OKC exercises in 

a restricted range of motion four weeks postoperatively (Van Melick et al., 2016; 

Andrade et al., 2020). The main advantage of incorporating CKC exercise is 

improving knee flexion after surgery, and the OKC extension exercise improved 

quadriceps strength after ACLR without increasing graft laxity (Mikkelsen et al., 2000; 

Jewiss et al., 2017; Forelli et al., 2023). 

2.4.3 Eccentric vs Concentric contractions 

A combination of eccentric and concentric contractions improved quadriceps and 

hamstring strength during the execution of these exercises (Kotsifaki et al., 2023). 

Eccentric OKC exercise training effectively targets quadriceps weakness after ACLR 

(Lepley et al., 2015; Vidmar et al., 2020). 

 

2.4.4 High-intensity vs Low-intensity ST ACLR exercises 

High-intensity (8RM) training from 14 weeks postoperatively was introduced to a 

group of ACLR patients with no adverse effect on knee joint stability and contributed 

to faster recovery of leg extension muscle power (Bieler et al., 2014). Both High-

intensity and Low-intensity do not have enough evidence to support their position.  

 

2.5 EXERCISE DOSAGE/PRESCRIPTION OR DOSE-RESPONSE 

RELATIONSHIP 

Exercise dosing refers to the repetitions, sets, intensity, duration, frequency, number 

of total exercises, and progression of each exercise while conducting an ACLR 

rehabilitation exercise program. The question remains how specific exercise dosage 

variables may influence the effectiveness of ACLR treatment (Young et al., 2018). A 

significant variation in these variables can impact the outcomes of a specific 

treatment. Currently, level-one evidence indicates a lack of consensus on an optimal 

ACLR rehabilitation program and no clarity concerning the exercise dosage and 

delivery (Van Melick et al., 2016; Culvenor et al., 2022; Kotsifaki et al., 2023). 

Expecting one optimal dosage is unrealistic, but with ACLR clinical trials that 



 

 

17 

adequately report the critical components of exercise dosage, clinicians can make 

informed decisions when prescribing ACLR strengthening exercises targeting the 

pathophysiology of ACLR surgery (Augustsson, 2013; Goff et al., 2018; Culvenor et 

al., 2022). 

 

2.6 TARGETED STRENGTH TRAINING (ST) TO IMPROVE 

PATHOPHYSIOLOGICAL ALTERATIONS AFTER ACLR 

Understanding ACLR surgical impact on the knee joint's neuromuscular function 

should enable practitioners to target this alteration through evidence-based ACLR ST 

exercise configurations (Tayfur et al., 2021). Quadriceps arthrogenic muscle inhibition 

(AMI) seems to be a challenge to treat after ACLR (Sonnery-Cottet et al., 2018; 

Pietrosimone et al. (2022). AMI is a presynaptic, ongoing reflex inhibition of 

musculature surrounding a joint after swelling or damage to structures (Hopkins et 

al., 2000). It is a natural response designed to protect the joint from further damage, 

but consequently, altered neuromuscular responses like quadriceps activation failure 

(QAF) are caused by this neural inhibition from central drivers (Norte et al., 2021). 

The peripheral effect of AMI plays out in quadriceps weakness characterised by a 

decrease in 

• voluntary muscle activation, 

• rate of force development, and  

• strength deficits after the ACLR participants conducted a rehabilitation program 

(Tayfur et al., 2021).  

 

A further extension of these peripheral morphological alterations is quadriceps Type 

l and Type ll muscle fiber atrophy and a reduction in satellite cell activation, which are 

necessary to increase muscle strength after ACLR (Palmieri-Smith et al., 2015; 

Noehren et al., 2016). Working towards the optimal ST stimuli targeting ACLR 

pathophysiological alterations on tissue (Type l and ll muscle fibers) and cellular level 

(satellite cell activation), one should focus on the primary objective of the 

strengthening exercise (Thomson et al., 2015). ACLR rehabilitation programs can 

include a diversity of strengthening exercises targeting endurance, hypertrophy, 

maximum strength, or power/rate of force development deficits after ACLR (Welling 



 

 

18 

et al., 2019; Maestroni et al., 2020; Maestroni et al., 2021). These objectives can be 

defined by the repetitions, sets, magnitude of load, etc., that drive the adaptational 

process from left to right (Figure 2.1) (Spiering et al., 2008; Thomson et al., 2015).  

 

Predicting the optimal molecular responses, like muscle growth or strength 

improvement, as the primary aim during ACLR exercise rehabilitation, clinicians 

should adhere to recommended ST physiological principles based on the repetition 

maximum (RM) continuum (Figure 2.2) to effectively prescribe ACLR exercise 

dosages (Beachle & Earl, 2008).  

 

  

Figure 2.1: Reporting of the exercise descriptors (EDs) that drive molecular adaptational responses 
(developed by the researcher and adapted from Thomson et al., 2015)  

 

Reporting of ACLR strengthening exercises descriptors (EDs) considering the 

repetition maximum (RM) continuum 

Classifying ST EDs into the main categories of the repetition continuum (endurance, 

hypertrophy, maximum strength, power/rate of force development) with their 

individual loading parameters (repetitions, sets, tempo, rest, velocity, intensity, etc.) 

can emphasise a range of ST modes necessary to incorporate into ACLR 

rehabilitation programs. Schoenfeld et al. (2021: 32) are of the opinion that "repetition 



 

 

19 

maximum continuum as the number of repetitions performed at a given magnitude of 

load, which results in specific adaptations as follows: 

• A low repetition scheme with heavy loads (from one to five repetitions per set with 

80% to 100% of 1-RM optimises strength increases (Figure 2.2, number 1). 

• A moderate repetition scheme with moderate loads (from eight to 12 repetitions 

per set with 60% to 80% of 1RM) optimises hypertrophic gains (Figure 2.2, 

number 2). 

• A high repetition scheme with light loads (15+ repetitions per set with loads below 

60% of 1RM) optimises local muscular endurance improvements" (Figure 2.2, 

number 3). 

Figure 2.2: Repetition maximum (RM) continuum (Beachle & Earl, 2008) 

 

Literature proposes that clinicians working with ACLR patients adopt targeted 

rehabilitation strategies that focus on lower loads initially, progressing towards 

maximum strength in the later phases of ACLR rehabilitation (Lorenz et al., 2010; 

Maestroni et al., 2021). Evidence of a progressive ST modal (endurance, 

hypertrophy, and maximum strength focused) indicates a high value for restoring 

quadriceps and hamstring strength deficits in ACLR amateur male and professional 

soccer players (Welling et al., 2019; Maestroni et al., 2023). Reporting the exercise 

dosages from high-level ACLR interventions may enable clinicians to duplicate the 

result of evidence-based ACLR studies.  

 

Unfortunately, an alarming gap in ACLR rehabilitation exists due to the inadequate 

reporting of resistance intensity over the entire spectrum of the RM continuum 

1 

2 

3 



 

 

20 

(Augustsson, 2013; Goff et al., 2018). More specifically, level-one evidence indicated 

a dearth of reporting the intensity of power and ST exercises in the late stage (>6 

months) of ACLR rehabilitation programs (Nichols et al., 2021). Subsequently, a 

compound effect may develop between non-sporting physiotherapists that lack 

knowledge and skill in performing the later phases of ACLR rehabilitation, including 

ST exercise prescription and poor reporting of ST EDs utilised in ACLR programs 

(Van Melick et al., 2017; Barton et al., 2021: Vlok et al., 2022). Therefore, research 

and clinical practice must follow best practice guidelines for reporting EDs and the 

proper execution thereof in ACLR clinical setting. 

 

2.7 BEST PRACTICE STRENGTH TRAINING (ST) GUIDELINES TO REPORT 

ACLR ST DURING ACLR EXERCISE REHABILITATION PROGRAMS  

ACLR rehabilitation literature recommended the usage of best practice ST guidelines 

like the American College of Sports Medicine (ACSM) and other supplementary 

literature to inform ACLR exercise programs about ST exercise dosages (Risberg et 

al., 2007; Ratamess et al., 2009). Toigo and Boutllier et al. (2006) reported that 

guidelines specific for resistance training interventions allow us to report 13 important 

specific ST configurations.  

 

2.8 CORE OUTCOMES SET OF ACLR STRENGTHENING EXERCISE 

DESCRIPTORS (EDS) 

Williamson et al. (2017:280) elaborated on the importance of formulating a core 

outcome set (COS) defined as "a list of outcomes, which experts have recommended 

that researchers should measure and report if they are undertaking a research study 

in a particular area". The COS goal in ACLR strength training (ST) is to standardise 

the EDs reported across studies and in clinical practice. 

 

2.9 IMPROPER REPORTING OF ACLR STRENGTH TRAINING (ST) EXERCISE 

DESCRIPTORS (EDS) 

 

Unfortunately, ACLR ST EDs (sets, tempo, repetitions, velocity, rest, intensity, etc.) 

are poorly reported in Levels 1-4 ACLR rehabilitation intervention studies (Nichols et 



 

 

21 

al., 2021; Vlok et al., 2022). High-quality reporting is needed to improve quality 

appraisal, enable evidence synthesis and replication, and improve translation in 

clinical settings (Bartholdy et al., 2019; Hansford et al., 2022). We do not know 

whether high-quality ACLR ST programs should target these alterations by reporting 

the ST EDs after ACLR injury. 

  



 

 

22 

CHAPTER 3 

 

SCOPING REVIEW 

_________________________________________________________________ 

 

This chapter will focus on the scoping methodology and the scoping review article.  

 

3.1 INTRODUCTION 

In the healthcare system, we all agree that “As the drive towards evidence-based 

practice has gathered pace, increasing numbers of systematic reviews reporting on 

the effectiveness of treatments and procedures have been published by, for example, 

the Cochrane Collaboration, an international body supported in the UK by the UK 

Cochrane Centre based in Oxford, and the NHS Centre for Reviews and 

Dissemination (CRD) at the University of York” (Arksey & O'Malley, 2005:19). 

Furthermore, according to Arksey and O'Malley (2005: 19), “this rapid growth in 

undertaking reviews of the literature has resulted in a plethora of terminology to 

describe approaches. However, despite the different names used in literature 

reviews, all literature reviews share certain essential characteristics, namely: 

• Collecting,  

• Evaluating, and  

• presenting the available research evidence”.   

More recently, the field of evidence synthesis has seen the emergence of “scoping 

reviews”, which are very similar to “systematic reviews” in that they follow a structured 

process. However, it is important to note that scoping reviews are performed for 

different reasons and have some key methodological differences (Munn et al., 2018).  

It is also important to note that there is no universally accepted definition or purpose 

for a scoping review (Daudt et al., 2013; Pham et al., 2014); however, the main 

characteristic of this method is that it provides an overview of a broad topic (Moher 

et al., 2015; Pham et al., 2014). Moher et al. (2015: 4) also stated “that a scoping 

review allows for a more general question and exploration of the related literature 



 

 

23 

rather than focusing on providing answers to a more limited question”. Davis et al. 

(2009) agreed and stated that the strength of scoping reviews lies in the development 

and intellectual creativity process. Peterson et al. (2016) concluded that the 

“methodology for a scoping review comprised similar systematic activities completed 

in any review, including: 

• Focus on a specific topical area,  

• a well-defined research question,  

• rationale regarding inclusion and exclusion criteria, and  

• clearly defined procedures and responsibilities for all researchers”. 

According to Munn et al. (2018:1), “Scoping reviews are now seen as a valid 

approach in those circumstances where systematic reviews are unable to meet the 

necessary objectives or requirements of knowledge users. There now exists clear 

guidance regarding the definition of scoping reviews, how to conduct scoping reviews 

and the steps involved in the scoping review process (see Appendix B)”. Munn et al. 

(2018:1) concluded that “researchers may conduct scoping reviews instead of 

systematic reviews where the purpose of the review is to identify knowledge gaps, 

scope a body of literature, clarify concepts or to investigate research conduct. While 

useful in their own right, scoping reviews may also be helpful precursors to systematic 

reviews and can be used to confirm the relevance of inclusion criteria and potential 

questions”.   

 

Thus, a scoping review design was used due to the exploratory nature of our research 

question.  Therefore, the aim of this scoping review was “to determine which strength 

training (ST) exercise descriptors (EDs) are reported in ACLR rehabilitation research.  

Our secondary aim was to evaluate how the reporting in these studies compares to 

international standards of reporting ST Eds”. From the literature, it is clear that a well-

executed scoping review on ACLR rehabilitation has the potential to inform 

biokineticists, physios, and other clinicians in practice. 

  



100 | february 2022 | volume 52 | number 2 | journal of orthopaedic & sports physical therapy 
 

[ literature review ] 
 

ARNOLD VLOK, BK1 • NICOL VAN DYK, PT, PhD2,3
 

DERIK COETZEE, PhD1 • HEGE GRINDEM, PT, PhD4,5
 

 

Exercise Descriptors That Determine Muscle 
Strength Gains Are Missing From Reported 
Anterior Cruciate Ligament Reconstruction 

Rehabilitation Programs: A Scoping 
Review of 117 Exercises in 41 Studies 

 

uscle weakness after anterior cruciate ligament 
reconstruction (ACLR) is persistent and associated with 
abnormal biomechanics,48,61 poor knee function,5,14,44-46 new 
knee injury,27,42 and development of osteoarthritis.49,60

 

Six months after ACLR, up to 40% of 

patients have side-to-side differences 

in quadriceps strength.45 Additionally, 

patients had moderate side-to-side dif- 

ferences in isometric and concentric 

quadriceps strength, significant differ- 

U OBJECTIVE: To (1) describe which strength 

training exercise descriptors are reported in 

anterior cruciate ligament reconstruction (ACLR) 

rehabilitation research, and (2) compare the cur- 

rent standards of reporting ACLR strength training 

exercise descriptors to international best-practice 

strength training guidelines. 

U DESIGN: Scoping review. 

U LITERATURE SEARCH: We searched the MED- 

LINE, PsycINFO, CINAHL, SPORTDiscus, Academic 

Search, ERIC, Health Source: Nursing, Health 

Source: Consumer, MasterFILE, and Africa-Wide 

Information databases. 

U STUDY SELECTION CRITERIA: We included 
level I to IV studies of ACLR rehabilitation pro- 

grams with 1 or more reported strength training 

exercise descriptors. We used a predefined list of 

19 exercise descriptors, based on the American 

College of Sports Medicine (ACSM) exercise 

recommendations, the Consensus on Exercise 

Reporting Template (CERT), and the Toigo and 

Boutellier exercise descriptor framework. 

U DATA SYNTHESIS: Completeness and the standard 

of reporting exercise descriptors in ACLR rehabilita- 

tion programs were assessed by means of interna- 

tional best-practice strength training standards. 

U RESULTS: We extracted data on 117 exercises 

from 41 studies. A median of 7 of the 19 possible 

exercise descriptors were reported (range, 3-16). Re- 

porting of specific exercise descriptors varied across 

studies, from 95% (name of the strength training 

exercise) to 5% (exercise aim, exercise order). On 

average, 46%, 35%, and 43% of the exercise de- 

scriptors included in the ACSM, CERT, and Toigo and 

Boutellier guidelines were reported, respectively. 

U CONCLUSION: Key exercise descriptors for 

muscle strength gains are not reported in studies 
on ACLR rehabilitation. Only the exercise name, 

number of exercises, frequency, and experimental 

period were reported in most of the studies. J Or- 

thop Sports Phys Ther 2022;52(2):100-112. Epub 

16 Nov 2021. doi:10.2519/jospt.2022.10651 

U KEY WORDS: anterior cruciate ligament recon- 

struction, CERT, exercise descriptors, intervention 
reporting, strength training 

ences in eccentric quadriceps strength, 

and moderate differences in isometric 

hamstring strength 2 years after ACLR.77 

The proposed drivers of persistent mus- 

cle weakness after ACLR are changes in 

muscle morphology,10,58 atrophy-inducing 

cytokines in the knee joint,55,85 and neuro- 

logical alterations at cortical and spinal 

levels.65
 

The most accessible approach to tar- 

get muscle weakness is to use various 

types of strength training exercises.51,63 

Because muscle weakness persists after 

rehabilitation, standard strength train- 

ing may not be sufficient, and clinicians 

should target the neurophysiological ori- 

gins of weakness with, for example, joint 

aspiration, corticosteroid injection, or 

electromagnetic modalities.48 However, 

another explanation for persistent weak- 

ness after ACLR rehabilitation could be 

 

 

1Department of Exercise and Sport Sciences, University of the Free State, Bloemfontein, South Africa. 2High-Performance Unit, Irish Rugby Football Union, Dublin, Ireland. 3Sports 

Medicine Section, Faculty of Health Sciences, University of Pretoria, Hatfield, South Africa. 4Oslo Sports Trauma Research Center, Department of Sports Medicine, Norwegian 

School of Sport Sciences, Oslo, Norway. 5Stockholm Sports Trauma Research Center, Department of Molecular Medicine and Surgery, Karolinska Institute, Stockholm, Sweden. 

The study protocol was approved by the University of the Free State Health Sciences Research Ethics Committee (reference number UFS-HSD2019/1889/2502). No funding was 

received for this review. Dr Grindem is an associate editor of the JOSPT. The authors certify that they have no affiliations with or financial involvement in any organization or 

entity with a direct financial interest in the subject matter or materials discussed in the article. Address correspondence to Arnold Vlok, PO Box 11899, Universitas, Bloemfontein, 

South Africa 9321. E-mail: vlok.optimalmovement@gmail.com U Copyright ©2022 JOSPT®, Inc 

M 

mailto:vlok.optimalmovement@gmail.com


journal of orthopaedic & sports physical therapy | volume 52 | number 2 | february 2022 | 101 

 

 

A 

 

 

that programs are not following best 

practice for strength training.21
 

To improve muscle performance 

outcomes, a strength training program 

should follow the proposed laws of mech- 

anotransduction,39 exercise specificity,40 

and the specific adaptations to imposed 

demands principle. Failure to improve 

muscle strength after ACLR could, 

therefore, be caused by faulty program- 

ming of exercise descriptors (eg, exercise 

type, frequency, and load).54 To determine 

whether the full potential of strength 

training was realized in previous litera- 

ture, we need more knowledge about the 

exercise descriptors that are reported in 

ACLR rehabilitation studies. 

Exercise descriptors that impact the 

result of strength training are well de- 

scribed in key exercise physiology publi- 

cations. In 2006, Toigo and Boutellier79 

(T&B) reviewed mechanobiological de- 

terminants of muscle hypertrophy and 

presented exercise descriptors that target 

these determinants. Ratamess et al66 pro- 

posed guidelines and progression models 

for resistance training in the position 

stand statement of the American College 

of Sports Medicine (ACSM). Slade et al74 

developed the Consensus on Exercise 

Reporting Template (CERT) to improve 

the reporting of essential exercise compo- 

nents across all evaluative study designs. 

These international standards col- 

lectively cover a comprehensive list of 

exercise descriptors that influence the 

outcomes of strength training programs. 

Therefore, the primary aim of this 

scoping review was to determine which 

strength training exercise descriptors are 

reported in ACLR rehabilitation research. 

Our secondary aim was to evaluate how 

the reporting in these studies compares 

to international standards of reporting 

strength training exercise descriptors. 

METHODS 
 

 

Protocol and Registration 
scoping review design was used 

due to the exploratory nature of the 

research question, where the aim 

was to determine which strength training 

exercise descriptors are reported in ACLR 

rehabilitation research. Study quality and 

risk-of-bias assessments do not influ- 

ence scoping review outcomes and were 

therefore not performed.1 We followed 

the 5-stage methodological framework 

proposed by Arksey and O’Malley,1 us- 

ing the Preferred Reporting Items for 

Systematic reviews and Meta-Analyses 

extension for Scoping Reviews (PRISMA- 

ScR)80 guidelines to map the available 

ACLR exercise descriptors. The review 

was registered prospectively through the 

Joanna Briggs Institute web page 

(https://joannabriggs.org/systematic- 

review-register) and the Open Science 

Framework online platform (https://doi. 

org/10.17605/OSF.IO/62VYA). 

 

Eligibility Criteria 
We included randomized trials, cohort 

studies, cross-sectional studies, case re- 

ports, and case-control studies in the 

scoping review. The search was lim- 

ited to studies published in the English 

language. Studies that reported ACLR 

strength training exercise descriptors 

between January 1990 and April 2021 as 

part of rehabilitation were included. We 

chose this time frame to limit the review 

to recent studies and thereby reflect cur- 

rent clinical practice. 

Inclusion in this scoping review was 

based on the following eligibility criteria. 

Participants Men and women (aged 16 

years and older) with ACLR in isolation 

or in combination with meniscus repair/ 

resection or cartilage surgery were in- 

cluded. The ACLR could be performed 

with either patellar tendon or hamstring 

tendon autografts. Studies that included 

patients who had ACLR with allografts 

and anterior cruciate ligament (ACL) re- 

pair were excluded, as differences in graft 

strength, fixation strength, and function- 

al tension can influence rehabilitation.28 

Articles were excluded if the studied par- 

ticipants were nonsurgically treated after 

ACL injury, had other associated grade lll 

ligamentous knee injuries combined with 

ACL injury, or had significant concomi- 

tant injuries to any area other than the 

knee. 

Exercise Intervention We included stud- 

ies that described strength training exer- 

cises, defined as exercises with a fixed 

mass as the means of resistance (eg, ankle 

weights, plate-loaded resistance training 

machines, free weights, or resistance 

bands). A priori defined strength train- 

ing descriptors are described in TABLE 

1. We excluded studies that described 

strength training only in combination 

with supplementary modalities, such as 

neuromuscular electrical stimulation, 

blood flow restriction training, isokinet- 

ics, or cryotherapy. 

Time At least 1 strength training exer- 

cise descriptor had to be reported in the 

rehabilitation program between 2 and 12 

months post ACLR. 

Context We included studies in which 

rehabilitation was performed in any set- 

ting (home-based, gym-based, or clinic- 

based rehabilitation). 

 

Information Sources and Search 
The librarian and first author (A.V.) com- 

piled key phrases and words to search the 

different databases (Appendix D). A 

librarian- assisted computer search of 

MEDLINE, PsycINFO,  CINAHL,  

SPORTDiscus, 

Academic Search, ERIC, Health Source: 

Nursing, Health Source: Consumer, 

MasterFILE, and Africa-Wide Informa- 

tion was conducted in October 2019 and 

updated in April 2021. The first author 

(A.V.) did a hand search of all references 

in all included papers to identify poten- 

tially eligible articles that were missed 

during the electronic database search. 

 

Study Selection 
All references were downloaded into an 

Excel (Microsoft Corporation, Red- 

mond, WA) spreadsheet screening tool, 

specifically developed by a librarian 

(Helena VonVille) for literature reviews. 

All duplicates were removed before the 

screening process. Two independent 

screeners (A.V. and D.C.) conducted the 

level 1 initial screening process of each 

https://joannabriggs.org/systematic-
https://doi.org/10.17605/OSF.IO/62VYA
https://doi.org/10.17605/OSF.IO/62VYA


[ literature review ] 

102 | february 2022 | volume 52 | number 2 | journal of orthopaedic & sports physical therapy 

 

 

 

 

 

 

 

 

 

 

 

 

  

   

 

article. To ensure interscreener reliabil- 

ity, the reviewers performed 1 training 

session before the screening process. 

Two reviewers (A.V. and D.C.) inde- 

pendently screened titles and abstracts 

for relevance. We compared and sum- 

marized the results within the custom- 

ized Excel spreadsheet workbook. The 

remaining studies were independently 

screened by the same reviewers in full 

text to determine eligibility, and reasons 

for exclusion were reported (Appendix 

D). Any disagreements between 

reviewers were resolved in a consensus 

meeting. Duplicate interventions were 

excluded, and we included the 

intervention with the most 

comprehensive description of exercises. 

The scoping review focused only on the 

extent to which studies re- ported the 

strength training exercise descriptors. 

The review did not focus on the outcome 

(efficiency or effectiveness) of any 

intervention. 

Data Extraction 
We reviewed full-text articles, supple- 

mentary files, and referenced articles to 

locate data for extraction. Data ex- 

traction was primarily performed by 1 

reviewer (A.V.) and verified by a second 

(D.C.). To ensure that the data extraction 

was consistent, a random sample of the 

included studies (ie, 5% of the complete 

list of retrieved studies) was extracted in 

duplicate (A.V. and D.C.). 

The 19 descriptors (TABLE 1) obtained 

from different sources (ACSM, T&B, and 

CERT) were extracted as the primary 

strength training descriptors. Two of 

these templates (T&B and CERT) have 

previously been used in studies evaluat- 

ing exercise descriptors.3,12,29 We com- 

posed the list of descriptors based on 

available guidelines on strength training 

recommendations (ACSM),66 strength 

training exercise physiology (T&B),79 and 

consensus recommendations for report- 

ing exercise interventions (CERT).74 The 

screening authors reviewed and selected 

19 descriptors a priori for data extraction 

through a consensus approach (TABLE 1). 

For all studies included in the review 

and for all strength training exercise de- 

scriptors (TABLE 1), the presence of a given 

exercise descriptor in a given study was 

coded as binary data (1 is present, 0 is 

absent). Additionally, we extracted data 

that described any clinical indicators that 

would cause adjustment to the strength 

training program (eg, pain or effusion). 

 

Data Management and Analysis 
The percentage of studies that reported 

the exercise descriptor (out of the total 

number of studies included) was calcu- 

lated. In addition, we calculated the per- 

centage of exercise descriptors reported 

in a given study (out of the total number 

of exercise descriptors stipulated in each 

of the 3 guidelines). These percentages 

were calculated as averages for each pub- 

lication year in the period from 1992 to 

 
 
 
 
 
 

Descriptor Definition ACSM T&B CERT 

Exercise name The name of the exercises prescribed x x  

Experimental period The duration of the entire program (eg, 12 weeks)  x x 

Number of exercises The number of exercises prescribed per session x   

Frequency The number of sessions per week x x x 

Adherence The extent to which the patient performed the prescribed program   x 

Repetitions The number of movements in a set x x x 

Exercise progress The progression of individual exercises (eg, increase in repetitions, load, and speed) x  x 

Exercise type The mode of exercise selected for a training program (eg, neuromuscular control exercises or strength training) x   

Program progress The progression of the entire program (eg, increase in the number of exercises or sessions per week)   x 

Sets The number of cycles of repetitions performed. Sets are separated by a rest interval x x x 

Load The amount of resistance assigned to an exercise set x x x 

Range of motion The degree of movement around a specific joint during an exercise  x x 

Rest The duration of recovery time between sets x x x 

Tempo The velocity at which an exercise is performed x  x 

Muscle action The type of muscle action during a repetition (eg, concentric, isometric, or eccentric) x x  

Muscular voluntary failure Whether exercises should be performed to the point of muscular voluntary failure (eg, repetitions performed  x x 



journal of orthopaedic & sports physical therapy | volume 52 | number 2 | february 2022 | 103 

 

 

 

 

2020, together with rolling averages, us- 

ing a window size of 5 (FIGURE 1). 

RESULTS 
 

 

he search yielded 754 studies 

after 7 hand-searched articles were 

added. After duplicates were re- 

moved, 420 studies remained for title 

and abstract screening. After applying 

the eligibility criteria, a total of 41 stud- 

ies were included in the review (FIGURE 2). 

 

Baseline Study Characteristics 
The demographic characteristics of the 

41 studies included in the analy- sis are 

summarized in TABLE 2. In total, 28 

randomized controlled trials (68%), 

6 prospective cohort studies (15%), 3 

cross-sectional studies (7%), 3 case re- 

ports (7%), and 1 case series (2%) were 

included. Collectively, the studies rep- 

resent 1964 individuals who underwent 

rehabilitation after ACLR, 1492 (76%) 

men and 472 (24%) women aged 16 to 56 

years. The ACLR was performed with 

either a patellar tendon (63%) or ham- 

strings tendon (37%) autograft. 

 

Rehabilitation Setting 
Experienced clinicians supervised the ma- 

jority (30/41 studies, 73%) of ACLR reha- 

bilitation programs in sports clinics, gyms, 

or hospital-based facilities. Fewer rehabili- 

tation programs were entirely unsuper- 

vised: home based (9/41 studies, 22%), 

or home based combined with supervised 

booster sessions (2/41 studies, 5%). 

 

Reported Strength Training Exercise 
Descriptors in ACLR Rehabilitation 

Research 
A total of 117 ACLR strength training 

exercises were described in the 41 stud- 

ies. The studies reported between 3 and 

16 of the 19 exercise descriptors (FIGURE 

3), with a median of 7 exercise descrip- 

tors reported. The name of the strength 

training exercises, number of exercises, 

and the experimental period were the 

descriptors most often documented in the 

included studies (FIGURES 3 and 4). 

The number of exercises used and the fre- 

quency of sessions were reported 71% to 

83% of the time (FIGURE 4). Across the dif- 

ferent studies, experimental periods most 

often lasted 3 to 6 months (24/41, 59%), 

and patients most often performed 2 to 3 

exercise sessions per week (20/41, 49%). 

Supervised sessions varied from 2 (8/41 

studies, 20%) to 3 sessions (17/41 stud- 

ies, 41%) per week. There was, however, 

a considerable variation in sessions per 

week, from 2 to 10. The most frequently 

prescribed exercises to improve muscle 

strength were leg press (19/41 studies) 

and leg extension (20/41 studies). 

Fewer than half of the studies reported 

exercise type, exercise progress, program 

progress, repetitions, sets, adherence, 

range of motion, and magnitude of load 

(FIGURE 4). Collectively, 44% to 46% of 

studies described number of repetitions, 

exercise progress, exercise type, program 

progress, and sets (FIGURE 4). Of the 117 

exercises described across the studies, 53 

(45%) included information on the num- 

ber of repetitions. Tempo, rest, range of 

motion, and load magnitude were all 

reported in 20% to 34% of the studies. 

Only 34% (14/41) of the studies specified 

the magnitude of load, which was com- 

 

 

 

 

 
 

  

 
  

 

 
 

 

 

 
 

 

  

  

  

 

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[ literature review ] 

104 | february 2022 | volume 52 | number 2 | journal of orthopaedic & sports physical therapy 

 

 

 

monly 50% to 80% of 1-repetition maxi- 

mum (1RM). 

Only 5% to 15% of studies reported the 

exercise descriptors of muscular voluntary 

failure, exercise aim, training duration, 

muscle action, and exercise order (FIGURE 4). 

 

Clinical Status of ACLR Knee 

During the Rehabilitation 
Fewer than half of the studies (18/41, 

44%) reported that exercises were adjust- 

ed based on the clinical status of the knee. 

Pain and effusion were 2 key indicators 

that were noted in 16/41 (39%) studies. 

 

Reporting of ACLR Rehabilitation 

Research Compared With International 

Strength Training Standards 
The average annual reporting values of 

the strength training exercise descrip- 

tors for the time period of 1992 to 2020 

for the ACSM (FIGURE 1A), T&B (FIGURE 1B), 

and CERT (FIGURE 1C) guidelines were 

summarized in FIGURE 1. Average annual 

ACLR exercise descriptor reporting var- 

ied between 17% and 78% when com- 

pared to ACSM guidelines. There was a 

10% increase in the reporting of ACSM 

exercise descriptors from 2002 (rolling 

average, 35%) to 2020 (rolling average, 

45%). For the T&B framework, ACLR 

exercise descriptor documentation varied 

between 10% and 77%. 

The reporting of items 5, 7, 11, and 13 

of the CERT guidelines (adapted for this 

study; TABLE 1) is presented in FIGURE 1C, 

with 13 descriptors to evaluate the ACLR 

intervention programs’ reporting quality. 

Exercise descriptor reporting using the 

CERT guidelines varied between 0% and 

76%. The rolling averages demonstrated 

large variability in the reporting of the 

exercise descriptors for all 3 guidelines 

(FIGURE 1). The average percentages of 

ACLR exercise descriptors documented 

(1992-2020) for each source were 46% 

(ACSM), 35% (CERT), and 43% (T&B). 

DISCUSSION 
 

 

n studies on ACLR rehabilitation, the 

exercise name, the duration of the 

rehabilitation period, the number of 

exercises in the program, and the fre- 

quency of training sessions per week were 

frequently reported. The remaining 15 ex- 

ercise descriptors included in international 

standards of strength training were infre- 

quently reported (by 5% to 49% of studies). 

 

How Is Strength Training Prescribed 

in ACLR Rehabilitation Studies? 
Only 4 of the 19 exercise descriptors were 

consistently documented in our sample 

(FIGURE 4), and it is difficult to interpret 

or reproduce ACLR strength training 

programs when so few exercise descrip- 

tors are reported. The poor reporting also 

means that we cannot conclude that mus- 

cle weakness persists in patients who fol- 

low best practice for strength training.21 

Clinicians should therefore not discount 

strength training as a main factor to re- 

gain muscle strength after ACLR. 

 

Studies identified via database Full-text studies identified via 
search, n = 747   

       
 

    
    

 
    
      
      

    
     

 
 

 
Studies included for 

    

 

 

abstract, n = 420 

 

 

eligibility, n = 101 

 
 
 

 
 
 
 
 
 
 
 
 
 
 
 
 
 

 

 

     

      

with fixed mass as resistance, n = 11 

ACL repair, or ACL injuries, n = 13 

(0-2 months after surgery), n = 3 

abstracts, updates, or studies in a 
non-English language, n = 16 

         

combination with supplementary 
modalities, n = 6 

     

injuries combined with ACL injury, n = 1 

screening, n = 319 

     
     
     

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journal of orthopaedic & sports physical therapy | volume 52 | number 2 | february 2022 | 105 

 

 

 

 

Strength Training and Muscle 
Weakness After ACLR 
Although many factors influence success- 

ful rehabilitation and return to sport post 

ACLR,59 muscle weakness after ACLR is 

driven by 2 main factors: a decrease in the 

cross-sectional area (atrophy) and 

arthrogenic muscle inhibition (quad- 

riceps activation failure).38,56,78 Accord- 

ing to the ACSM best-practice strength 

training guidelines, strength training to 

increase the cross-sectional area should 

be performed with 6 to 12 repetitions, 2 

to 4 sets, 60 to 120 seconds of rest be- 

tween sets, and a load magnitude of 60% 

to 80% of 1RM. Exercises should include 

concentric, isometric, and eccentric 

muscle actions. The program’s proposed 

duration should be 8 to 12 weeks, with a 

frequency of 2 to 4 sessions per week.40 It 

should be noted, however, that more re- 

cent research has found that hypertrophy 

can be achieved with both low-load and 

high-load strength training.71
 

Of the studies on ACLR rehabilitation, 

90% reported the experimental period’s 

duration and 71% included frequency. 

However, only 44% of studies reported 

sets, 46% reported repetitions, 34% re- 

ported load magnitude, 20% reported 

rest, and 15