Sustained muscle deoxygenation vs sustained high VO2 during high-intensity interval training in sprint canoe-kayak

Recent data suggests that peripheral adaptations, i.e. the muscle ability to extract and use oxygen, may be a stronger predictor of canoe-kayak sprint performance compared to VO2max or central adaptations. If maximizing the time near VO2max during high-intensity interval training (HIT) sessions is believed to optimize central adaptations, maximizing the time near maximal levels of muscle desaturation could represent a critical stimulus to optimize peripheral adaptations. Purpose Therefore, the purpose of this study was to assess the VO2, muscle oxygenation and cardiac output responses to various HIT sessions, and to determine which type of HIT elicits the lowest muscle oxygenation and the longest cumulated time at low muscle O2 saturation. Methods Thirteen well-trained canoe-kayak athletes performed an incremental test to determine VO2max and peak power output (PPO), and 4 HIT sessions (short intervals SI-15:40x[15sec at 115%PPO, 15sec at 30%PPO]; SI-30:20x[30sec at 115%PPO, 30sec at 30%PPO]; sprint interval training (SIT):6x[30sec all-out, 3min30 rest]; long supramaximal intervals LSI-60:6x[1min at 130%PPO, 3min rest]) on a canoe or kayak ergometer. Portable near-infrared spectroscopy monitors (Moxy) were placed on the latissimus dorsi (LD), biceps brachii (BB), and vastus lateralis (VL) during every session to assess changes in muscle O2 saturation (SmO2, % of physiological range). Results Short intervals elicited a longer time at >90%VO2max (SI-15:8.1±6.2min, SI-30:6.8±4.6min), compared to SIT (1.7±1.3min, p=0.006 and p=0.035) but not LSI-60 (4.1±1.7min). SIT and LSI-60 elicited the lowest SmO2 in the VL (SIT:0±1%, LSI-60:8±9%) compared to SI-15 (26±12%, p90% of maximal deoxygenation in all 3 muscles, with effect sizes ranging from small to very large. Conclusions Short interval training performed on a canoe/kayak ergometer elicits the longest time near VO2max, potentially conducive to VO2max improvements, but SIT is needed in order to maximize muscle deoxygenation during training, which would potentially conduct to greater peripheral adaptations.