Effects of extra load position on energy expenditure in treadmill running

The present study was designed to investigate how much running economy would be affected by changing the placement of extra load on running subjects. Twenty-four volunteer college students, 18 males and 6 females between 19 and 25 years ran on a treadmill at three different speeds (6, 8, and 10 km h(-1)). Energy expenditure was measured in O(2 )l min(-1). Subjects were tested under three experimental conditions, presented in random order; a normal (baseline) condition, and two different conditions in which the subjects had to carry extra load. The extra load added 10% to the subjects' body mass, and was placed symmetrically on the subjects' shoulders or around their waists. Loading of the subjects affected running economy negatively in both conditions but more so for the shoulder condition. It is argued that the difference between the conditions is due to the fact that the subjects' balance control deteriorated when their centre of gravity was elevated by adding extra load on their shoulders.