PERFORMANCE EFFICIENCY DECREASES ACROSS EVENT TIME – JUSTIFICATION FOR TECHNIQUE CONCENTRATION

Uitslag, T. P., Galiart, R., Foster, C., Porcari, J. P., Daanen, H., Noordhof, D. A., & de Konig, J. J. (June 03, 2010). Changes in gross efficiency during high intensity exercise. Presentation 2237 at the 2010 Annual Meeting of the American College of Sports Medicine, Baltimore, Maryland; June 2-5.

red line

This study evaluated the effect of ventilation and core temperature on gross mechanical efficiency before and after a time-trial exercise. Gross mechanical efficiency was measured during submaximal (50% POmax ) exercise in trained cyclists (M = 11; F = 8) before and immediately after a four-minute time-trial (100%POmax ), and during a control bout where the power output during the time-trial period remained at 50%POmax . Gas exchange was measured throughout the exercise bout and core temperature was measured using a radio pill.

Gross mechanical efficiency was reduced following the time-trial and had not recovered to control values within 10 minutes post-exercise. Change in gross mechanical efficiency was well correlated with the changes in ventilation (r = -.94), but not with changes in core temp (r = -.45). Gross mechanical efficiency decreased from ~18.0% at the beginning to ~15.5% at the end of the time-trial. This would result in a significant reduction in the aerobically attributable energy supply during the time-trial.

Implication. Gross mechanical efficiency decreases across the course of a four-minute high-intensity time-trial exercise. This suggests that gross mechanical efficiency measured before a time-trial (aerobic and anaerobic components) would not be represented in the actual time-trial. Because of the reduction in efficiency as fatigue accrues, athletes would do well to concentrate on technique features associated with efficiency to minimize the decrement.

Return to Table of Contents for this issue.

red line