BODY-MASS-MODIFIED RUNNING ECONOMY AND STEP LENGTH IN ELITE MALE MIDDLE-DISTANCE AND LONG-DISTANCE RUNNERS

To minimize the influence of body mass on oxygen uptake (VO2) during r unning, submaximal and maximal VO2 should preferentially be expressed as ml.kg(-0.75). min(-1). In this study, the levels of such body-mass- modified running economy were investigated at different velocities in elite runners and related to step lengths and anthropometric measures. Twenty-six Swedish National Team middle- and long-distance runners pe rformed submaximal (4 velocities) and maximal treadmill tests. In 17 r unners repeated (2-4) tests were performed within 6 months. The maxima l oxygen uptake (VO(2)max; 214 vs 202 ml.kg(-0.75).min(-1)) and runnin g velocity at 4 mmol.l(-1) blood lactate were higher in the long-(n = 12) than in the middle-distance group (n = 14). The oxygen uptake at 1 5 km.h(-1) (VO2 15) was lower (129 vs 138 ml.kg(-0.75).min(-1), P < 0. 01) acid the VO2/velocity slope higher in the long-distance runners, w ith similar VO2 18 in the two groups. Step lengths at 18 (168 vs 173 c m) and 15 km.h(-1) did not differ significantly between the groups, bu t the increase in step length per km.h(-1) velocity raise was greater in the middle-distance runners. Step lengths at these velocities were positively related to body mass and stature, negatively to relative le g length. Stature and leg length were greater in runners displaying lo w VO2 15 , whereas no corresponding difference was seen for VO2 18 . T he figures for running economy at 15 and 18 km.h(-1) were poorly relat ed to the concomitantly determined step lengths at the respective velo cities. In conclusion, the present results demonstrate greater running economy slope but lesser step length slope in elite long- as compared to middle-distance runners. Furthermore, even body-mass-modified runn ing economy seems to be poorly related to the step length.