Some physiological effects of deep underground mining and the relationship with physical work capacity and functional work capacity assessment outcomes
Dürrheim, Erna Theresia
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Motivation: The South-African deep level gold mining industry has adapted in many ways, as the pursuit for gold has led deep into the earth core, where rock face temperatures measure around 60°C. Ventilation adapted through engineering developments like refrigeration systems, creating cooler work environments to an extent. Despite these developments the risks of high ambient temperatures coupled with strenuous work and dehydration remains, leading to alternative methods of control that have to indicate whether employees have the necessary functional capacity to perform daily work tasks. Objectives: The objectives of this study were: to measure and compare the physiological effects of the tasks performed by workers in an underground mining environment; To measure the soundness of heart rate as a gauge of work stress in real-life work conditions, taking into account the stressors that influence it; to determine the efficacy of functional and physical work capacity assessments as a method of determining work readiness. Methods: A study group (n = 16) was chosen to represent the “most exposed” work population, all of whom have previously passed the functional work capacity and physical work capacity assessments. The assessments were repeated and the maximal oxygen uptake assessment was done. The participants were divided into two groups (n = 8) according to their work areas. Measurements were taken over a period of eight consecutive shifts. Each group was later divided into three groups as per the work they performed. Dehydration was determined through urine analysis and body weight changes. Heart rate was observed continuously through a heart rate monitor and oral temperature was measured on an hourly basis. Results: The shift durations seen during this study were much longer than the customary 8-hour work day. The mean HR results of group I, which was suspected of having the most strenuous work, were very similar to the results for group II and III. This group did, however, have the highest % heart rate ≥ 120 beats per minute and mean cumulative heart beats, group III having the lowest. All of the groups were found to be mildly dehydrated at the end of their shifts, the urine specific gravity indicating that the participants were generally already considerably dehydrated at the onset of the shifts. Group I was the only group whose mean heart rate had a statistically significant correlation (r ≥ 0.5) with % weight loss. There was a statistically significant (p ≤ 0.05) correlation between heart rate and mean oral temperature for all of the groups. The participants that passed the functional work capacity and physical work capacity assessments were found to have performed comparatively better during the real-time shifts than those that failed. Conclusions: Although there were several employees that had a high mean maximum heart rate, none of the mean heart rates were higher than the self-pacing rate of 110 beats per minute. This ability of self- pacing was seen in the way the participants were able to manage energy expenditure by alternating between heavy and lighter tasks. A great concern is the fact that all of the participants had a % weight loss (0.9 – 2.8% weight loss) indicative of mild dehydration after the shifts, on top of morning urine specific gravity samples (1.020 – 1.025) showing signs of considerable dehydration. Several correlations were found between the functional work capacity and physical work capacity assessments and maximum temperature, maximum heart rate and maximal oxygen uptake, suggesting a significant relationship between the real life situation and the homogenous laboratory setting. comparing the employees that passed the functional work capacity and physical work capacity assessment to those that failed, a marked difference was seen in their respective performances. The groups that passed had a lower mean heart rate and maximum heart rate and higher maximal oxygen uptake. It may, therefore, be concluded that the functional work capacity and physical work capacity assessments provide a valid evaluation of an individual’s work capacity and potential to cope with the varying demands of underground work.
- Health Sciences