The highest velocity and the shortest duration permitting attainment of VO2max during running

Abstract

The severe-intensity domain has important applications for the prescription of running training and the elaboration of experimental designs. The objectives of this study were: 1) to investigate the validity of a previously proposed model to estimate the shortest exercise duration (T_LOW) and the highest velocity (V_HIGH) at which VO₂max is reached during running, and 2) to evaluate the effects of aerobic training status on these variables. Eight runners and eight physically active subjects performed several treadmill running exercise tests to fatigue in order to mathematically estimate and to experimentally determine T_LOW and V_HIGH. The relationship between the time to achieve VO₂max and time to exhaustion (Tlim) was used to estimate T_LOW. V_HIGH was estimated using the critical velocity model. V_HIGH was assumed to be the highest velocity at which VO₂ was equal to or higher than the average VO₂max minus one standard deviation. T_LOW was defined as Tlim associated with V_HIGH. Runners presented better aerobic fitness and higher V_HIGH (22.2 ± 1.9 km.h^-1) than active subjects (20.0 ± 2.1 km.h^-1). However, T_LOW did not differ between groups (runners: 101 ± 39 s; active subjects: 100 ± 35 s). T_LOW and V_HIGH were not well estimated by the model proposed, with high coefficients of variation (> 6%) and a low correlation coefficient (r<0.70), a fact reducing the validity of the model. It was concluded that aerobic training status positively affected only V_HIGH. Furthermore, the model proposed presented low validity to estimate the upper boundary of the severe-intensity domain (i.e., V_HIGH), irrespective of the subjects’ training status.