Experimental Studies of Muscular Fatigue of Bengalees with Increasing Work Loads under Different Environmental Conditions

Abstract

The effects of increasing work by 1 kg/sec per minute, measured on Müller's magnetic-type bicycle ergometer, on healthy males, have been noted under different environmental conditions. Experiments in a hot humid environment (at 34°c with relative humidity 90%) and a comfortable environment (at about 23°c with low humidity of 30%) were performed and effects on ventilation, heart rate, oxygen consumption, oxygen pulse, extraction ratio and blood lactate concentration, etc., were noted. On the average, work could be continued for up to 20 minutes, by which time the subject felt fatigue and exhaustion. The intensity of work during the last minute was 1200 kg per minute.

The blood volume of the subjects at rest (sitting posture on the ergometer) was determined and stroke volume calculated from heart rate. Cardiac output was estimated both at rest and in the working condition by the dye dilution technique to evaluate the subjects' haemodynamics in relation to work causing muscular fatigue.

The results show that increasing the work load produces fatigue by stressing cardiac activity to the limit: other parameters having some reserve capacity. During the first few minutes the work done mainly by the aerobic mechanism is marked by lower lactic acid concentration in the blood. The work of the anaerobic mechanism comes at a much later phase of the task.