Obesity does not increase external mechanical work per kilogram body mass during walking

Walking is the most common type of physical activity prescribed for the treatment of obesity The net metabolic rate during level walking (W/kg) is similar to 10% greater in obese vs. normal weight adults. External mechanical work (W-ext ) is one of the primary determinants of the metabolic cost of walking, but the effects of obesity on W-ext have not been clearly established. The purpose of this study was to compare W-ext between obese and normal weight adults across a range of walking speeds We hypothesized that W-ext, (J/step) would be greater in obese adults but W-ext normalized to body mass would be similar in obese and normal weight adults We collected right leg three-dimensional ground reaction forces (GRF) while twenty adults (10 obese, BMI = 35.6 kg/m(2) and 10 normal weight, BMI = 22.1 kg/m(2)) walked on a level, dual-belt force measuring treadmill at six speeds (0.50-175 m/s). We used the individual limb method (ILM) to calculate external work done on the center of mass Absolute W-ext (J/step) was greater in obese vs. normal weight adults at each walking speed, but relative W-ext (J/step/kg) was similar between the groups. Step frequencies were not different. These results suggest that W-ext is not responsible for the greater metabolic cost of walking (W/kg) in moderately obese adults (C) 2009 Elsevier Ltd. All rights reserved.