Physiological determinants of time to exhaustion during intermittent treadmill running at vV̇O2max

Abstract

Previous studies have reported large between-subject variations in the time to exhaustion during intermittent running at the velocity at V̇O 2max (vV̇O2max). This study aimed to determine which physiological factors contribute to this variability. Thirteen male runners (age 38.9 ± 8.7 years) each completed five treadmill running tests; two incremental tests to determine V̇O2max, vV̇O2max, the lactate threshold velocity (vLT) and the running velocity-V̇O 2 relationship; the third test to determine the time to exhaustion during continuous running at vV̇O2max (tlimcont); the fourth to determine the maximal accumulated oxygen deficit (MAOD); the fifth to determine the time to exhaustion during intermittent running at vV̇O 2max (tlimint). Relief intervals during the intermittent test were run at 70% vV̇O2max. The vLT-vV̇O2max difference was significantly correlated with tlimint (r = - 0.70; p = 0.007). The correlation coefficient increased to r = - 0.83 (p < 0.001) when the difference between the relief interval velocity and the vLT was deducted from the vLT-vV̇O2max difference (theoretically representing the net depletion of the MAOD during each work/relief interval cycle). The main finding of this study was that 49 % of the variance in tlimint was explained by the vLT-vV̇O2max difference, compared to 74% for tlimcont. However, a further 20% of unique variance in t limint could be explained with the inclusion of the relief interval velocity-vLT difference. Theoretically, runners with the largest relief interval velocity-vLT difference will replete their anaerobic capacity to a greater extent during each relief interval, thereby increasing time to exhaustion. © Georg Thieme Verlag KG Stuttgart.