Hypoxia Increases Muscle Hypertrophy Induced by Resistance Training

Abstract

Purpose:Recent studies have shown that low-intensity resistance training with vascular occlusion (kaatsu training) induces muscle hypertrophy. A local hypoxic environment facilitates muscle hypertrophy during kaatsu training. We postulated that muscle hypertrophy can be more efficiently induced by placing the entire body in a hypoxic environment to induce muscle hypoxia followed by resistance training.Methods:Fourteen male university students were randomly assigned to hypoxia (Hyp) and normoxia (Norm) groups (n = 7 per group). Each training session proceeded at an exercise intensity of 70% of 1 repetition maximum (RM), and comprised four sets of 10 repetitions of elbow extension and fexion. Students exercised twice weekly for 6 wk and then muscle hypertrophy was assessed by magnetic resonance imaging and muscle strength was evaluated based on 1RM.Results:Muscle hypertrophy was significantly greater for the Hyp-Ex (exercised fexor of the hypoxia group) than for the Hyp-N (nonexercised fexor of the hypoxia group) or Norm-Ex fexor (P < .05, Bonferroni correction). Muscle hypertrophy was significantly greater for the Hyp-Ex than the Hyp-N extensor. Muscle strength was significantly increased early (by week 3) in the Hyp-Ex, but not in the Norm-Ex group.Conclusion:This study suggests that resistance training under hypoxic conditions improves muscle strength and induces muscle hypertrophy faster than under normoxic conditions, thus representing a promising new training technique.

Intermittent hypoxic resistance training: Is metabolic stress the key moderator?

“…These studies are summarized in [11,17]. However, other investigations using similar training loads but with extended inter-set recovery intervals (90-120 s) have demonstrated no added benefit for training under hypoxia [12,13].…”

“…Research has demonstrated that hypertrophic and strength responses can be enhanced by breathing hypoxic air during low-load (20% 1RM) [6,10] and moderate-load (70% 1RM) [11] resistance training. However, some more recent evidence has provided conflicting results, reporting no additional benefit for muscular development following resistance training in systemic hypoxia [12,13].…”

Physical Performance During High-Intensity Resistance Exercise in Normoxic and Hypoxic Conditions

“…Recently, researchers have begun to investigate whether resistance exercise performed while breathing normobaric hypoxic air can augment muscular development, similarly to BFR exercise (17,18,21,22,25). Manimmanakorn et al (21) investigated the adaptive responses to 5 weeks of low-intensity intermittent hypoxic resistance training (IHRT; 20% 1RM), with the fraction of inspired oxygen (F I O 2 ) being adjusted to maintain arterial oxygen saturation (SpO 2 ) at ~80%.…”

“…Additionally, Nishimura et al (25) reported that 6 weeks of moderate-intensity IHRT (70% 1RM; F I O 2 =0.16) resulted in significant hypertrophic gains in untrained males, despite no change after matched training in normoxia. Muscle strength was also found to increase significantly after only 3 weeks of IHRT, whereas significant strength increases in the normoxia group required 6 weeks (25).…”

“…While research suggests that low-moderate load IHRT can offer hypertrophic and strength benefits above the equivalent normoxic training (21,22,25), the efficacy of highintensity IHRT has not yet been examined. However, due to the demanding nature of highintensity resistance exercise and the importance placed on physical performance during training, it is important to first consider whether additional hypoxia might impact negatively on participants' ability to perform adequately during training.…”