Prevalence and blood profile analysis of South African gold-miners working underground who present with exercise-associated muscle cramps at work

Abstract

Background: Almost a hundred years after the first reports on the possible aetiology of muscle cramping in mine workers, the debate on the mechanism and contributing factors to the development of cramping rages on and we are no closer to preventing cramping. The current theories of the “Electrolyte depletion and Dehydration model” or “Salty Sweat” with the addition of fatigue (Bergeron, 2003; Eichner, 2007; Armstrong, et al., 2007) and the current, and more accepted “Altered Neuromuscular Control” hypotheses (Schwellnus, 2008) are still polarising the debate surrounding EAMC. Aims: The aim of this study was not to prove or disprove any of the current theories surrounding EAMC. This study’s aims were to describe the prevalence and certain environmental, biochemical and haematological variables in gold miners working underground who presented with exercise-associated muscle cramps (EAMC) at work. It further aimed to formulate or describe the ‘normal’ profile of haematological and biochemical changes during a shift, in the mining population. This “normal” control data were also generated to assist in the interpretation of the haematological and biochemical variables from the group who presented with EAMC. Methods: This study consisted of two parts: Part 1 was a retrospective descriptive study of the blood profiles of underground mine workers who presented with EAMC, together with biological factors relating to these workers. The procedure for data collection for the cramp group was to extract routine data from the clinical notes of miners who presented to the medical stations with EAMC. Part 2 was a prospective study consisting of a collection of blood-samples, before and after an 8 hour shift (2 hours commuting and 6 hours of physical labour), on a volunteer group of healthy underground mine workers not presenting with cramps. The data were sent for statistical analyses. Due to the exploratory nature of this study, descriptive statistics were primarily used to report the findings. Trends were observed and expanded on based on available literature and specialist consultation. Results: Due to the large amount of data generated by the study, the discussion of the results was presented under four main category headings. These categories were chosen following a literature review and specialist consultation on the significant findings from the study. These categories were hydration and electrolyte disturbances, muscle damage, muscle fatigue and inflammation. The “normal” or control participants were well to slightly over hydrated individuals, with progressive muscle injury (increased CK levels, but no increase in myoglobin) during a working week. The participants experience muscle fatigue with a slight WCC reaction as a result of his daily labours. The individual mostly worked in cramped spaces with heavy and sometimes vibrating tools or walked long distances or stood for long periods of time. They were also able to regulate their body temperature and homeostasis with minimal stress on their liver and kidneys. The participants who presented with EAMC mainly performed heavy physical labour but there were also the group that remained in cramped positions for prolonged periods. They showed possible signs of dehydration, muscle fatigue, muscle damage (raised myoglobin and CK levels), and inflammation. Conclusion: There seems to be an unnecessary polarisation between those for and those against the inclusion of electrolyte and dehydration into the aetiology of EAMC. One of the main arguments against the inclusion of these hypotheses (electrolyte & dehydration) is that the proponents basically fail to link how a systemic abnormality may cause a local disruption in homeostasis. This is a sound argument if we consider electrolyte disturbances and dehydration to be the sole cause of cramping. One should rather see this as part of a collective subset of contributing factors that each add to priming the body’s muscles for developing cramps. Single or groups of muscles that do then cramp are being triggered to cramp in the “primed” environment by factors such as fatigue.