Daily stability in energy cost of running, respiratory parameters and stride rate among well-trained middle distance runners.

The purpose of this study was to quantify total intraindividual variability in energy cost of running (C), ventilation (VE), respiratory frequency (RF), heart rate (HR), lactate concentration (La) and stride rate (SR) at usual training pace in French elite middle distance runners. Subjects were monitored four times a week during submaximal treadmill tests at 75% VO2max speed (15.8 +/- .02 km.h-1). No significant differences (p > .05) were found between tests in C, VE, RF, HR, SR. Significant day to day differences were found in La (0.5 +/- 0.3, p < .025). However, a wide range of individual coefficients of variation were observed for C (0.2-10.6), VE (0.9-8.8) and RF (0.7-9.3). SR appears to be the most stable parameter (0.2-2.6). No correlation was found between these individual variations. These results suggest that in well-trained runners C, VE, RF, HR and SR are stable measures for assessing the efficacy of procedures aimed at improving the energy cost of running. For the speed used in testing, the respiratory parameters and energy cost of running presented a wide range of individual variation whereas stride rate appeared to be a very stable measure.