DAILY STABILITY IN ENERGY-COST OF RUNNING, RESPIRATORY PARAMETERS ANDSTRIDE RATE AMONG WELL-TRAINED MIDDLE-DISTANCE RUNNERS

The purpose of this study was to quantify total intraindividual variab ility in energy cost of running (C), ventilation (VE), respiratory fre quency (RF), heart rate (HR), lactate concentration (La) and stride ra te (SR) at usual training pace in French elite middle distance runners . Subjects were monitored four times a week during submaximal treadmil l tests at 75 % VO(2)max speed (15.8+/-.02 km.h(-1)). No significant d ifferences (p>.05) were found between tests in C, VE, RF, HR, SR. Sign ificant day to day differences were found in La (0.5+/-0.3, p<.025). H owever, a wide range of individual coefficients of variation were obse rved 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-train ed 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 c ost of running presented a wide range of individual variation whereas stride rate appeared to be a very stable measure.