The effect on energy expenditure of walking on gradients or carrying burdens

The effectiveness of people walking while carrying burdens and/or on gradients has been of interest to anthropologists for some time. No empirical equation exists, however, to assess the energetic expenditure of individuals traveling downhill with burdens and whether or not all people increase their energetic expenditure over unburdened level travel when carrying relatively light burdens (<20% of body mass) remains unclear. To begin to rectify this lacunae, gait parameters, physiological variables, and the energetic expenditure of 11 adults were assessed as they walked with burdens of 5 and 10 kg on a level treadmill and while they walked unburdened on gradients +/-8 and +/-16%. These data were then compared to predictive equations and data available from the literature. Velocity and body mass were combined with gradient and burden mass, where appropriate, as independent covariates to create predictive equations, which explained >80% of the variation in energetic expenditure. These new equations are appropriate for predicting energetic expenditure in people carrying burdens of <20% of total body mass or walking up and downhill at gradients of <20%.