Influence of Work-Interval Intensity and Duration on Time Spent at a High Percentage VO2max During Intermittent Supramaximal Exercise

The purpose of this study was to examine the effect of work-interval duration (WID) and intensity on the time spent at, or above, 95% V̇O2max (T95 V̇O2max) during intermittent bouts of supramaximal exercise. Over a 5-week period, 7 physically active men with a mean (±SD) age, height, body mass, and V̇O2max of 22 ± 5 years, 181.5 ± 5.6 cm, 86.4 ± 11.4 kg, and 51.5 ± 1.5 ml·kg−1·min−1, respectively, attended 7 testing sessions. After completing a submaximal incremental test on a treadmill to identify individual oxygen uptake/running velocity relationships, subjects completed a maximal incremental test to exhaustion to establish V̇O2max and subsequently (from the aforementioned relationship) the minimum velocity required to elicit V̇O2max (vV̇O2max). In a random order, subjects then carried out 3 intermittent runs to exhaustion at both 105% and 115% vV̇O2max. Each test used a different WID (20 s, 25 s, or 30 s) interspersed with 20-second passive recovery periods. Results revealed no significant difference in T95 vV̇O2max for intermittent runs at 105% versus 115% vV̇O2max (p = 0.142). There was, however, a significant effect (p < 0.001) of WID on T95 V̇O2max, with WIDs of 30 seconds enabling more time relative to WIDs of 20 seconds (p = 0.018) and 25 seconds (p = 0.009). Moreover, there was an interaction between intensity and duration such that the effect of WID was magnified at the lower exercise intensity (p = 0.046). In conclusion, despite a number of limitations, the results of this investigation suggest that exercise intensities of approximately 105% vV̇O2max combined with WIDs greater than 25 seconds provide the best way of optimizing T95 V̇O2max when using fixed 20-second stationary rest periods.