Oxygen uptake during the last bouts of exercise incorporated into high-intensity intermittent cross-exercise exceeds the (V)overdot O₂max of the same exercise mode

Oxygen uptake ((V) over dot O-2) was measured during a non-exhaustive high-intensity intermittent cross-exercise (HIICE) protocol consisting of four alternating bouts of 20 s running (R) and three bouts of bicycle exercise (BE) at -160% and -170% maximal oxygen uptake ((V) over dot O(2)max), respectively, with 10 s between-bout rests (sequence R-BE-R-BER-BE-R). The(V) over dot O-2 during the last BE ([52.2 +/- 5.0] mL center dot kg(-1)center dot min(-1)) was significantly higher than the(V) over dot O(2)max of the BE ([48.0 +/- 5.4] mL center dot kg(-1)center dot min(-1), n = 30) and similar to that of running. For clarifying the underlying mechanisms, a corresponding HIICE-protocol with BE and arm cranking ergometer exercise (AC) was used (sequence AC-AC-BE-AC-BE-AC-AC-BE). In some experiments, thigh blood flow was occluded by a cuff around the upper thigh. Without occlusion, the(V) over dot O-2 during the AC ([39.2 +/- 7.1] mL center dot kg(-1)center dot min(-1) [6th bout]) was significantly higher than the(V) over dot O(2)max of AC ([30.2 +/- 4.4] mL center dot kg(-1)center dot min(-1), n = 7). With occlusion, the corresponding(V) over dot O-2 ([29.8 +/- 3.9] mL center dot kg(-1)center dot min(-1)) was reduced to that of the(V) over dot O(2)max of AC and significantly less than the(V) over dot O-2 without occlusion. These findings suggest that during the last bouts of HIICE may exceed the of the specific exercise, probably because it is a summation of the(V) over dot O-2 for the ongoing exercise plus excess post-oxygen consumption (EPOC) produced by the previous exercise with a higher(V) over dot O(2)max.