title: Intensive cycle training with artificial gravity maintains muscle size during bed rest.
abstract: 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.
authors.affiliation: Research Center of Health, Physical Fitness & Sports, Nagoya University, Nagoya, Aichi, Japan. akima@nagoya-u.jp
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Akima
authors.forename: Keisho
authors.initials: K
authors.lastname: Katayama
authors.forename: Kohei
authors.initials: K
authors.lastname: Sato
authors.forename: Koji
authors.initials: K
authors.lastname: Ishida
authors.forename: Kazumi
authors.initials: K
authors.lastname: Masuda
authors.forename: Hiroki
authors.initials: H
authors.lastname: Takada
authors.forename: Yoriko
authors.initials: Y
authors.lastname: Watanabe
authors.forename: Satoshi
authors.initials: S
authors.lastname: Iwase
mesh_terms: 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