Abstract
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 (HIIT) 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 HIIT sessions, and to determine which type of HIIT 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 HIIT sessions (HIIT-15: 40x[15 s at 115%PPO, 15 s at 30%PPO]; HIIT-30: 20x[30 s at 115%PPO, 30 s at 30%PPO]; HIIT-60: 6x[1 min at 130%PPO, 3 min rest]; sprint interval training (SIT): 6x[30 s all-out, 3 min 30 rest]) on a canoe or kayak ergometer. Portable near-infrared spectroscopy monitors 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: HIIT-15 and HIIT-30 elicited a longer time >90%VO2max (HIIT-15: 8.1 ± 6.2 min, HIIT-30: 6.8 ± 4.6 min), compared to SIT (1.7 ± 1.3 min, p = 0.006 and p = 0.035) but not HIIT-60 (4.1 ± 1.7 min). SIT and HIIT-60 elicited the lowest SmO2 in the VL (SIT: 0 ± 1%, HIIT-60: 8 ± 9%) compared to HIIT-15 (26 ± 12%, p < 0.001 and p = 0.007) and HIIT-30 (25 ± 12%, p < 0.001 and p = 0.030). SIT produced the longest time at >90% of maximal deoxygenation in all 3 muscles, with effect sizes ranging from small to very large.Conclusions: Short HIIT 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.
Highlights
High-intensity interval training (HIIT) is considered one of the most effective training for improving performance in athletes from various sports (Buchheit and Laursen, 2013a)
In a literature review published in 2006, Midgley and McNaughton (2006) detailed the training characteristics that produce the longest time at or near VO2max. They concluded that, in order to maximize time spent near VO2max, work intervals of 15–30 s should be performed at an intensity of 90–105% of the minimal speed eliciting VO2max, and recovery intervals of 15–30 s should be performed at an intensity between 50% of VO2max and lactate threshold
We chose to only present SmO2 here, since recent studies have found that the Moxy monitor provides credible and reliable SmO2 values (McManus et al, 2018), but that total hemoglobin values had low variation during exercise and were probably not a valid indicator of blood volume (Crum et al, 2017). These results suggest that Sprint interval training (SIT) elicits a high muscle O2 demand, and while the optimal amount of time spent at high muscle deoxygenation in training is not known, it appears that SIT would be an ideal training session to elicit peripheral adaptations
Summary
High-intensity interval training (HIIT) is considered one of the most effective training for improving performance in athletes from various sports (Buchheit and Laursen, 2013a). In 1986, Wenger and Bell (1986) published a review of the literature, where they concluded that VO2max enhancement was positively related to exercise intensity, for intensities from 50 to 100% of VO2max, and showed that the greatest improvements occurred when training was performed at an intensity between 90 and 100% of VO2max. In a literature review published in 2006, Midgley and McNaughton (2006) detailed the training characteristics that produce the longest time at or near VO2max. They concluded that, in order to maximize time spent near VO2max, work intervals of 15–30 s should be performed at an intensity of 90–105% of the minimal speed eliciting VO2max (vVO2max), and recovery intervals of 15–30 s should be performed at an intensity between 50% of VO2max and lactate threshold
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