Intensive cycle training with artificial gravity maintains muscle size during bed rest.
BACKGROUND
The present study aimed to investigate the effect of intensive cycle training with short-arm centrifuge-induced hypergravity during bed rest on muscle size and function.


METHODS
This study involved 10 healthy men who were divided into 2 groups: a countermeasure group, BR-CM (n = 5); and a control group, BR-Cont (n = 5). The BR-CM subjects partook in intensive cycle training (to 90% of maximum HR) with short-arm centrifuge-induced artificial gravity on alternate days during 20-d bed rest. Muscle volume of the thigh and maximum voluntary contraction (MVC) during isometric knee extensions was measured before and after bed rest. Muscle functional magnetic resonance imaging (mfMRI) and electromyogram (EMG) of the quadriceps femoris were obtained during submaximal knee extension exercises at a load of 30% MVC.


RESULTS
The volume of the total thigh muscles was maintained in the BR-CM group (-1%), whereas it was not in the BR-Cont group (-9%, p < 0.05). MVC decreased in the BR-CM (7%) and BR-Cont groups (23%). EMG activity in the BR-CM group after bed rest was significantly lower than that of before; however, no significant change was found in the BR-Cont group. There were no significant changes in the resting and exercised mfMRI signals in either the BR-CM or BR-Cont groups.


CONCLUSIONS
These results suggest that intensive cycle training with hypergravity maintained the size of human skeletal muscles during bed rest.
Akima
Hiroshi
H
Research Center of Health, Physical Fitness & Sports, Nagoya University, Nagoya, Aichi, Japan. akima@nagoya-u.jp
Katayama
Keisho
K
Sato
Kohei
K
Ishida
Koji
K
Masuda
Kazumi
K
Takada
Hiroki
H
Watanabe
Yoriko
Y
Iwase
Satoshi
S
D000328:Adult; D001132:Arm / Q000502:physiology; D001510:Bed Rest; D004576:Electromyography; D015444:Exercise / Q000502:physiology*; D006801:Humans; D018471:Hypergravity / Q000009:adverse effects*; D008279:Magnetic Resonance Imaging; D008297:Male; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000033:anatomy & histology* / Q000502:physiology