HUMAN ENERGY-EXPENDITURE WHEN WALKING ON A MOVING PLATFORM

The assumption that working on board ship is more strenuous than compa rable work ashore was investigated in this study. Various physiologica l parameters ((V) over dotO(2), (V) over dotCO(2), (V) over dot(E) and HR) have been measured to determine the energy expenditure of subject s walking slowly on a moving platform (ship motion simulator). Twelve subjects (eight men and four women) walked either freely on the floor or on a treadmill at a speed of 1 m . s(-1). Platform motion was eithe r in a heave, pitch or roll mode. These three conditions were compared with a control condition in which the platform remained stationary. T he results showed that during pitch and roll movements of the platform , the energy expenditure for the same walking task was about 30% highe r than under the stationary control condition (3.6 J . kg(-1) . m(-1) vs 2.5 J . kg(-1) . m(-1), P < 0.05) for both walking on a treadmill a nd free walking. The heart rate data supported the higher energy expen diture results with an elevation of the heart rate (112 beats . min(-1 ) vs 103 beats . min(-1), P < 0.05). The heave condition did not diffe r significantly from the stationary control condition. Pitch and roll were not significantly different from each other. During all experimen tal conditions free walking resulted in a higher energy cost of walkin g than treadmill walking (3.5 J . kg(-1) . m(-1) vs 2.7 J . kg(-1) . m (-1), P < 0.05) at the same average speed. The results of this experim ent were interpreted as indicating that the muscular effort, needed fo r maintaining balance when walking on a pitching or rolling platform, resulted in a significantly higher work load than similar walking on a stable or a heaving floor, independent of the mode of walking. These results explain in part the increased fatigue observed when a task is performed on a moving platform.