Knee extensor and plantar flexor muscle size and function following 90 days of bed rest with or without resistance exercise.

• Skeletal muscle atrophy and strength loss induced by short-term simulated spaceflight are offset or attenuated by resistance exercise (RE). This study compared the effects of plantar flexor and knee extensor RE on muscle size and function in 17 healthy men (aged 26–41years) subjected to 90 days 6 head-down-tilt bed rest with (BRE; n=8) or without (BR; n=9) RE. The RE program consisted of coupled maximal concentric and eccentric actions in the supine squat (4 sets of 7 repetitions) and calf press (4·14) every third day employing a gravity-independent flywheel ergometer (FW). Prior to, and following bed rest, muscle volume was assessed using magnetic resonance imaging. Similarly, muscle strength and power and surface lectromyographic (EMG) activity were determined during maximal actions using FW or isokinetic dynamometry. In BR, knee extensor and plantar flexor muscle volume decreased (P<0.05) 18% and 29%, respectively. Torque or force and power decreased (P<0.05) 31–60% (knee extension) and 37–56% (plantar flexion) while knee extensor and plantar flexor EMG activity decreased 31–38% and 28–35%, respectively following BR. Muscle atrophy in BRE was prevented (P>0.05; knee extensors) or attenuated ()15%; plantar flexors). BRE maintained task-specific force, power and EMG activity. The decrease in non-task-specific torque was less (P<0.05) than in BR. The present data imply that the triceps surae and quadriceps muscles show different responsiveness to long-term bed rest with or without resistance exercise. The results also suggest that designing in-flight resistance exercise protocols for space travellers is complex and must extend beyond preserving

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Hälsovetenskap -- Idrottsvetenskap (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Health Sciences -- Sport and Fitness Sciences (hsv//eng)

MEDICIN OCH HÄLSOVETENSKAP  -- Medicinska och farmaceutiska grundvetenskaper -- Fysiologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Basic Medicine -- Physiology (hsv//eng)

Nyckelord

flywheel exercise

muscle atrophy

spaceflight

Sport science

Idrottsvetenskap

Sports

Idrott

Physiology

Fysiologi

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