An assessment of physical strain experienced by manual workers in brick laying operation - A case study in Nigeria

Despite rapid technological developments, heavy dynamic muscular work and manual material handling will continue to be required for execution of tasks associated with various occupations. This study examined the physical strain experienced by brick layers and the applicability of heart rate indices for measuring physical strain in brick laying operations in south-western region of Nigeria with focus on the maximum energy expenditure and physiological workload during work. It further examined the effect on the workers’ productivity. The heart rate of ten brick layers were recorded continuously throughout the working day and applied to heart rate indices. The average working heart rate was 122.8 bt. Min-1, while the pre-work resting heart was 70.5 bt. Min-1. The average physical workload (%HRR) rate was 47.26, while the ratio of working heart rate to resting heart rate was 1.74. The average ratio of working heart rate to 50% level was 0.98. The workers had a mean estimated maximum aerobic capacity (Vo2max) of 47.77 ml kg-1 min-1. The results showed that an average bricklayer expended high energy which classified brick laying work as heavy work. The energy expenditure was estimated to be 9 Kcal. Min.-1, work bout (Tw) and maximum work bout (Tmax) were estimated to be 5.5 minutes and 6.3 minutes respectively. Rest period (R) = 6.2 minutes. This study shows that heart rate indices can be used as an effective means of determining the physiological strain of subjects in applied field situations. There is need to redesign the work content of the aforementioned occupation in order to prevent excessive strain on the workers, which in turn will increase productivity. Manual workers should be tested and evaluated for their physical work capacity for a particular task