Occupational health in practice: Heart rate profile of the lathe machine workers

Context: Lathe machine work is an important unorganized sector in India. However, to date, no work physiological studies have been conducted among these workers to evaluate the physical strain involved in this work. Aim: The present study aims to determine the workload in different lathe machine tasks from working heart rates (HRs) and certain cardiac indices. Settings and Design: A cross-sectional study was conducted among 38 full-time male workers aged between 21 and 60 years. Methods and Materials: The HR was measured directly during the productive work phase, additional work phase, and work pauses. Two cardiac strain indices, viz., net cardiac cost and relative cardiac cost were derived. The workload was also judged according to some standard acceptable criteria of physical strain. Statistical Analysis Used: Mean and standard deviation were obtained for different categories of HR. Intergroup comparisons were conducted through one-way analysis of variance and the t-test. Results: The mean working HR was found to be 99 beats per minute. A maximal working HR of 105 ± 6.1 beats per minute with a corresponding relative cardiac cost of 26% was obtained during the additional work phase. Conclusions: The overall workload appeared to be moderate in nature. An acceptable criterion of cardiac cost of 30% appeared to be the most sensitive index in detecting workers experiencing a higher level of physical strain.