V.O2 responses to running speeds above V.O2max

This study compared V.O (2), heart rate (HR) and electromyographic (iEMG) responses to speeds above the velocity associated with V.O (2max) (v-V.O (2max)). Eight male, middle-distance runners performed a graded exercise test to determine V.O (2max) and v-V.O (2max) and runs to fatigue at 100 \% and 110 \% v-V.O (2max). Breath-by-breath V.O (2) and HR were continuously recorded; lactate [La (-)] measured pre- and post-run and iEMG measures of rectus femoris (RF) and vastus lateralis were recorded during the first and last 20 s of each run. Analysis indicated longer time to fatigue in the 100 \% v-V.O (2max) run with no differences between conditions for V.O (2) or HR amplitudes or post-run [La (-)] (p > 0.05). There were significantly faster tau values (p < 0.05) in the 110 \% condition in V.O (2) and HR. No significant correlations were observed between V.O (2) or HR tau values and time to fatigue. RF iEMG was significantly larger in 110 \% compared to 100 \% run in the first 20 s (p < 0.05). While no association between treadmill performance and V.O (2) response was evident, faster running speeds resulted in faster V.O (2) and HR responses, with no difference in amplitude or \% V.O (2max) attained. This may potentially be as a result of an increased muscle fibre recruitment stimulus during the faster running velocity resulting in faster cardiodynamic responses.