Effects of high-intensity intermittent cross-training on maximal oxygen uptake

We investigated the effects of high-intensity intermittent cross-training (HIICT) on maximal oxygen uptake (・VO 2 max). The HIICT consisted of alternating intermittent 20-s treadmill running (1 st , 3 rd , 5 th , and 7 th bouts) and 20-s bicycle exercise (2 nd , 4 th , and 6 th bouts) with a 10-s rest period. Each intensity for running and bicycling of the HIICT corresponded to an oxygen demand of ∼160% and ∼170% of the O 2 max, respectively. Fifteen healthy young males (aged [24 ± 1] yrs) were randomly assigned to training (TG, n = 8) and non-training control (CG, n = 7) groups. The TG completed this HIICT daily 4 days/week for 6 weeks. Significant group × time interactions were observed for both the running and bicycling O 2 max ( p < 0.001 each). After the training, the ・VO 2 max for both running ([57.4 ± 4.8] mL·kg −1 ·min −1 ) and bicycling ([50.6 ± 3.7] mL·kg −1 ·min −1 ) in the TG were significantly higher than those for running ( [50.1 ± 3.1] mL·kg −1 ·min −1 ) and bicycling ( [43.7 ± 3.6] mL·kg −1 ·min −1 ) in the CG, respectively ( p < 0.01 each). Post-hoc tests revealed a significant increase in ・VO 2 max for running and bicycling in the TG after the HIICT ( p < 0.001 each) but no significant difference in the CG. These results demonstrated that the newly developed HIICT increases the ・VO 2 max for both running and bicycling.