Cardio-Respiratory and Metabolic Changes during Continuous Uphill-Downhill Load Carriage Task

Abstract

Indian Army soldiers are deployed in hilly and mountainous regions of eastern and western part of the Himalayas to guard the borders. In this context they are required to march uphill and downhill with moderate to heavy load continuously for long duration. The physiological cost of such activities has been of specific interest for maintenance of optimum soldier performance. Studies on physiological changes during continuous uphill and downhill climbing are rare. A study was therefore undertaken to find the effect of uphill and downhill walk with load on the physiological parameters in laboratory conditions. Twelve soldiers with mean (± SD) age- 26.8 (± 3.9) yrs, height- 170.6 (± 3.2) cm and weight 66.2 (± 6.8) kg participated in the study as volunteers to measure the energy cost and physiological changes of continuous uphill and downhill load carriage task. The soldiers were subjected to treadmill walking at a speed of 3 km/ h. They had to undergo continuous uphill walking at 0, 5, 10, 15 and 20% gradients and downhill walking in the opposite manner. Participants walked 6 mins in each gradient. Total duration of walk was 60 min. The volunteers carried 10.7 and 21.4 kg load beside without load. Oxygen consumption (VO2), Heart rate (HR), and energy expenditure (EE), were measured breath by breath using Metamax 3B system throughout the test. Relative work load (RWL, %VO2max) was calculated as percentage of VO2max. Repeated measure ANOVAs were used to predict level of significance across the experimental conditions. The mean (± SD) VO2max of the participants was found to be 52.6 (± 3.8) ml/min/kg. All the physiological parameters increased significantly with the increase in uphill gradient irrespective of the loads. VO2, EE and %VO2max decreased till 5% downhill gradient, but slight increase was observed at the level walking. HR continued to decrease till the downhill walking reached 0% gradient with and without load. Relative work load reached above the recommended limit (35% of VO2max) at 10% and above uphill gradients in both the load conditions. This information will be helpful in making strategy for designing uphill and downhill load march in mountains for Army personnel and hitch hikers.