Nutritional assessment of professional rugby players in Mpumalanga: are requirements being met according to current sports nutrition standards?
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Date
2019-01
Authors
Van Aardt, Reon
Journal Title
Journal ISSN
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Publisher
University of the Free State
Abstract
Optimal sports nutrition is directly linked to success in sporting activities, yet research indicates that adequate knowledge of nutrition is often lacking in athletes. The results of several studies have shown that the dietary intakes and eating habits of rugby players often leave much to be desired.
Evidence-based nutrition principals and recommendations for athletes are continuously summarised by a number of organisations including the American College of Sports Medicine (ACSM) and the International Society of Sports Nutrition (ISSN). The current study aimed to assess the nutritional status of professional rugby players in Mpumalanga and compared the results to current sports nutrition guidelines.
A cross-sectional study design was applied in a total population (n=41) of professional rugby players, the Steval Pumas. Participants were over 18 years old and permanent team members. The study was approved by the Health Sciences Research Ethics Committee of the University of the Free State and the team management. All participants signed written informed consent.
A self-developed questionnaire and three 24-hour recalls were used to obtain information related to dietary intake and lifestyle behaviours (smoking and alcohol intake), as well as information related to socio-demographics (age, home language, level of education and current playing position in the team). This was completed by the researcher in a structured interview with each participant. Food Finder, a dietary analysis software program, was then used to estimate energy, macronutrient and micronutrient intake. Anthropometric measurements were taken by a level one accredited International Society for the Advancement of Kinanthropometry (ISAK) biokineticist, according to standardised techniques, to calculate Body Mass Index (BMI), body fat percentage and waist circumference.
The median age of participants was 26.1 years and the majority spoke Afrikaans (83%), while half had completed a tertiary qualification (51%). Player postions were fairly equally distributed with 54% of participants being forwards (prop, hooker, lock, flanker, or number 8 position), while the remaining 46% were backs (wing, centre, or full back).
The mean body weight of participants was 101kg and 12% were classified as “overweight” according to Boksmart standards (>118 kilogram [kg] for forwards; >100kg for backs). The mean body fat percentage of participants was 12.5%, well within the international recommendations for professional rugby players (8 – 17%), although median body fat percentages for the forwards (13.9%) and backs (10.1%) were slightly lower than national Boksmart standards.
Based on the recommendations of the ISSN, energy requirements for rugby players are 200 to 350 kilojoules (kJ) per kg body weight per day. In terms of carbohydrate requirements, 5 to 7 grams (g) per kg body weight are needed on an off day, and 6 to 10g per kg body weight are required on training and game days. The ISSN and ACSM further recommend a protein intake of 1.2 to 2.0g per kg body weight per day, while 30% of total daily energy intake should be from fat.
Only 37% of participants perceived their eating habits as “good.” This was confirmed by the fact that the majority of participants did not meet energy (95%), carbohydrate (100%), or fibre requirements (about 75%) on training and off days. In contrast to carbohydrate intake, all participants exceeded protein requirements. In terms of micronutrient intake, about 50% of participants had an intake of Thiamine and Vitamin E below the recommendations on training and off days, while 75% of participants consumed insufficient Vitamin C, as well as Calcium (85%) on these days.
In terms of associations, no significant difference was found between level of education and energy, carbohydrate, protein, fat, as well as micronutrient intake. There was also no significant difference in median energy and macronutrient intake of forwards and backline players. Although not statistically significant, there did seem to be a trend for backline players to consume slightly more energy on training days (12816kJ versus 11334kJ), with forwards consuming slightly more protein on training days (249g versus 228g). Interestingly, the micronutrient intake of participants that were using a supplement was not significantly different to that of participants that were not using a supplement, except for Thiamine on a training and off day, Vitamin B6 on a training day, Vitamin B12 on a training day, Iron on an off day and Zinc on a training day.
As expected, participants with a body fat percentage in the low category had a significantly lower BMI compared to those with a fat percentage in the normal category (95% CI = [0.3kg/m² ; 4.6kg/m²]). Participants with a body fat percentage in the low category also had a significantly lower waist circumference compared to those with a fat percentage in the normal category (95% CI = [2.0cm ; 7.0cm]). Similarly, participants with a body fat percentage in the low category had a lower median fat percentage compared to those in the normal category (95% CI = [2.4% ; 6.0%]). The median body fat percentage of backline players was significantly lower than that of the forward players, with a 95% CI for the median difference of [-5.3% ; -2.3%]. Finally, the median running distance covered by the backline players on an average field-work day was significantly higher than that of the forwards (p=0.0005).
In conclusion, although most participants maintained the desired body composition, dietary guidelines were not optimally adhered to and the importance of optimal nutrition did not enjoy the same level of attention as their physical training. The findings of the present study can provide valuable and useful information to the players and their coaches on adherence to dietary requirements for provincial rugby players. It is recommended that nutrition-related issues be addressed, since inadequate dietary intakes and unhealthy eating behaviours can negatively impact on nutritional status, overall health, quality of training, performance and recovery. Further research related to the barriers that prevent rugby players from following the guidelines is warranted, in order to motivate practical, cost-effective and relevant interventions.
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Keywords
Assessment, Exercise, Guidelines, Nutritional status, Rugby, Dissertation (M.Sc. (Dietetics))--University of the Free State, 2019