VO2 responses to running speeds above VO2 max.

This study compared V*O2, heart rate (HR) and electromyographic (iEMG) responses to speeds above the velocity associated with V*O2 max (v-V*O2 max). Eight male, middle-distance runners performed a graded exercise test to determine V*O2 max and v-V*O2 max and runs to fatigue at 100% and 110% v-V*O2 max. Breath-by-breath V*O2 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*O2 max run with no differences between conditions for V*O2 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*O2 and HR. No significant correlations were observed between V*O2 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*O2 response was evident, faster running speeds resulted in faster V*O2 and HR responses, with no difference in amplitude or % V*O2max attained. This may potentially be as a result of an increased muscle fibre recruitment stimulus during the faster running velocity resulting in faster cardio-dynamic responses.