VARIABILITY IN ENERGY-COST OF RUNNING DURING ONE TRAINING SEASON IN HIGH-LEVEL RUNNERS

The purpose of this study was to investigate the effect of training sp ecificity on a possible change in the energy cost of running over a pe riod of one training season in high level competition runners. Four mi ddle distance and four long distance runners participated in treadmill tests on three sessions after a specific training period. In each ses sion, every subject participated in two tests to determine, in the fir st test the maximal oxygen consumption and in the second test the ener gy cost of running. The second test was performed at 60% and 80% of Vm ax (maximal speed reached during the first test, respectively 12 and 1 6 km.h-1), and at 0% grade. The maximal oxygen uptake (VO2max, ml.kg-1 .min-1) increased significantly between the first and the last session (p < 0.05). For all the tests, long distance runners showed higher va lues of VO2max than middle distance runners (p < 0.00 1). During the y ear, there were no significant changes in energy cost (C, ml/kg-1.km-1 ) between the first and the last session (respectively at 60% and 80% vmax: 165+/-5,8 vs 164+/-4,9 and 167,5+3,5 vs 166,8+/-3,3), and no dif ferences were found between middle and long distance runners. An addit ion, no changes were found in lactate concentration or in respiratory exchange ratio during all the training season. Discussion set out the difficulty to conclude to a stability in energy cost of running. First by the fact that the energy cost reflects both positive and negative effects of training. Secondly, by the fact that high level runners are always in a competition season, and tend to perform training work at the same competition intensity.