Cycle ergometer exercise to counteract muscle atrophy during unilateral lower limb suspension.
BACKGROUND
Atrophy of the leg muscles is a serious consequence of disuse and occurs with prolonged exposure to microgravity. We investigated whether intense interval training on a cycle ergometer would prevent muscle changes during unilateral lower limb suspension (ULLS).


METHODS
This study involved 11 healthy men who were divided into 2 groups, one with training on a cycle ergometer (TRN, N=6) and the other a control group (CON, N=5). TRN performed intense interval training (up to 90% of maximum heart rate) on alternate days during 20 d of unloading. Maximum voluntary contraction (MVC) of the quadriceps femoris and volume of the thigh muscle were measured before and after unloading. Muscle functional magnetic resonance imaging (mfMRI), which reflects the contractile activity of the activating muscle, were acquired during submaximal dynamic knee extension exercises.


RESULTS
The MVC was significantly decreased in TRN (-11.1%) and CON (-18.7%). The total volume of the thigh muscles was maintained in TRN (-0.2%); however, a significant decrease was found in CON (-6.9%). The mfMRI signal increase for submaximal exercise did not change for TRN; however, it significantly increased for CON.


CONCLUSIONS
Although the power of this study was limited, these results suggest that training on a cycle ergometer counteracts some of the effects of unloading and merits further study as a potential countermeasure for muscle changes in microgravity.
Akima
Hiroshi
H
Research Center of Health, Physical Fitness & Sports, Nagoya University, Nagoya City, Aichi Prefecture, Japan. akima@nagoya-u.jp
Hotta
Norio
N
Sato
Kohei
K
Ishida
Koji
K
Koike
Teruhiko
T
Katayama
Keisho
K
D000328:Adult; D000704:Analysis of Variance; D001642:Bicycling / Q000502:physiology*; D016552:Ergometry; D017079:Exercise Tolerance; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D007866:Leg / Q000502:physiology*; D008279:Magnetic Resonance Imaging; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D009133:Muscular Atrophy / Q000517:prevention & control*; D011446:Prospective Studies; D013026:Space Flight; D014893:Weightlessness