Changes in mechanical work during severe exhausting running

The possible contribution of muscular work to the increase in oxygen uptake (O₂) over time during running was investigated on 11 adult males who were asked to run until exhaustion at 90 (3)% [mean (SD)] of their maximal aerobic velocity on a treadmill ergometer. Ground reaction forces, expired gases and EMG from leg muscles were collected for 30 s at min 3 and during the last minute of the run. Subjects ran for 829 (165) s and showed an increase in O₂ of 179 (93) ml.min^–1 between min 3 and exhaustion. Increased ventilation explained 41 (27)% of the increase in O₂. Stride frequency slightly decreased but no significant differences were found in the mechanical work or in integrated EMG. It was concluded that, in running, the increase in O₂ could not be related to a drift in muscle work.