Hypoxia increases muscle hypertrophy induced by resistance training.
OBJECTIVE
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 flexion. 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 flexor of the hypoxia group) than for the Hyp-N (nonexercised flexor of the hypoxia group) or Norm-Ex flexor (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.


CONCLUSIONS
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.
Department of Orthopaedic Surgery, Mie University Graduate School of Medicine, Tsu City, Mie Prefecture, Japan.
Akinobu
A
Nishimura
Masaaki
M
Sugita
Ko
K
Kato
Aki
A
Fukuda
Akihiro
A
Sudo
Atsumasa
A
Uchida
D000328:Adult; D006801:Humans; D006984:Hypertrophy / Q000503:physiopathology; D000860:Hypoxia / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D053580:Muscle Strength / Q000502:physiology; D018482:Muscle, Skeletal / Q000473:pathology*; D055070:Resistance Training; D055815:Young Adult