Influence of mechanical and metabolic strain on the oxygen consumption slow component during forward pulled running.

The possible influence of increased eccentric mechanical work on the increase in oxygen uptake ( V(.)O(2)) after 3 min of running (Delta V(.)O(2)) was investigated through forward pulled running. Ten subjects ran at individually predetermined constant velocity on a treadmill, while being pulled forward. Ground reaction forces, expired gas and EMGs from leg muscles were collected after 3 min and at the end of the run. V(.)O(2) and mechanical work were then calculated. The amplitude of Delta V(.)O(2) was 138 (139) ml x min(-1) [mean (SD)]. Increased ventilation explained only 8% of Delta V(.)O(2). Stride frequency slightly decreased, inducing a similar decrease in internal work and total mechanical work (all P<0.01), while integrated EMG showed no modifications. It was concluded that Delta V(.)O(2) does not come from either an increase in mechanical work production or an increase in muscular activity. Delta V(.)O(2) could come from a lower muscle efficiency that could be due to a modification of fibre type recruitment.