Cited by 307Spaceflight effects on biologyMuscle Physiology and DisordersCardiovascular and exercise physiology

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

Alkner, Bj�rn A., Tesch, Per A.·2004·European Journal of Applied Physiology

Abstract

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 degrees 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 x 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 electromyographic (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 muscle only.

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Registry

Crossref · 10.1007/s00421-004-1172-8

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53 of 53 references verified0 citation errors · 0 not checkable

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  • Resistance exercise every third day during 90-days bed rest was sufficient to completely offset the 20% reduction in knee extensor muscle size noted in resting control subjects.

    “resistance exercise every third day during 90-days bed rest was sufficient to completely offset the 20% reduction in knee extensor muscle size noted in the resting control subjects [92].”
  • Numerically established degeneration rates for the knee extensors differed by 5% to 80% dependent on the duration of disuse.

    “Numerically established degeneration rates for the knee extensors differed by 5% to 80% dependent on the duration of disuse (6, 18, 21–23).”
  • The aforementioned factors may cause cumulative effects, which may account for the particularly steep slope portion in muscle strength.

    “The aforementioned factors may cause cumulative effects (71, 72), which may account for the particularly steep slope portion in muscle strength (21, 93).”
  • Muscles are more or less apt to undergo atrophy in response to unloading or disuse depending on their topography and function.

    “Second, dependent on their topography and function (21), muscles are more or less apt to undergo atrophy in response to unloading or disuse (71, 72).”
  • Transferability to other body regions or contractile classes is limited by phenotype, fiber composition, function, and the muscles' task specificity.

    “With reference to Clark (70), the transferability to other body regions or contractile classes is limited by the phenotype (21), fiber composition (71), function [i.e., extensors or flexors (72)], and the muscles’ task specificity (70, 73, 74).”

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Authors
Alkner, B. A., & Tesch, P. A.
Affiliations
Karolinska Institutet (SE)
Venue
European Journal of Applied Physiology
Published
2004-08-27
Volume
93
Issue
3
Pages
294-305
ISSN
  • 0020-9376 (ISSN-L)
  • 1439-6319
  • 1439-6327
OpenAlex
W2093021904
Cited by
306
References
53
Citations by year
2026: 6 · 2025: 15 · 2024: 12 · 2023: 14 · 2022: 14 · 2021: 14 · 2020: 21 · 2019: 16 · 2018: 16 · 2017: 12 · 2016: 11 · 2015: 14 · 2014: 18 · 2013: 11 · 2012: 5
FWCI
9.25
Type
journal article
Language
en
Open access
closed
Locations
  • European Journal of Applied Physiology (publishedVersion)
  • PubMed (publishedVersion)
Funders
Swedish National Space Agency
Topics
  • Health Sciences › Medicine › Physiology › Spaceflight effects on biology
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Muscle Physiology and Disorders
  • Health Sciences › Medicine › Complementary and alternative medicine › Cardiovascular and exercise physiology
Keywords
muscle atrophy, resistance training, bed rest, simulated microgravity, head-down tilt, knee extensors, plantar flexors, muscle volume, muscle strength, muscle power, electromyography, triceps surae, quadriceps, spaceflight countermeasures, squatting
MeSH terms
Adult, Humans, Leg, Male, Exercise, Weightlessness Simulation, Muscle, Skeletal

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