Changes in muscle size, architecture, and neural activation after 20 days of bed rest with and without resistance exercise

Yasuo Kawakami*, Hiroshi Akima, Keitaro Kubo, Yoshiho Muraoka, Hiroshi Hasegawa, Motoki Kouzaki, Morihiro Imai, Yoji Suzuki, Atsuaki Gunji, Hiroaki Kanehisa, Tetsuo Fukunaga

*この研究の対応する著者

研究成果: Article査読

141 被引用数 (Scopus)

抄録

Nine healthy men carried out head-down bed rest (BR) for 20 days. Five subjects (TR) performed isometric, bilateral leg extension exercise every day, while the other four (NT) did not. Before and after BR, maximal isometric knee extension force was measured. Neural activation was assessed using a supramaximal twitch interpolated over voluntary contraction. From a series cross-sectional magnetic resonance imaging scans of the thigh, physiological cross-sectional areas (PCSA) of the quadriceps muscles were estimated (uncorrected PCSA, volume/estimated fibre length). Decrease in mean muscle force after BR was greater in NT [-10.9 (SD 6.9)%, P < 0.05] than in TR [0.5 (SD 7.9)%, not significant]. Neural activation did not differ between the two groups before BR, but after BR NT showed smaller activation levels. Pennation angles of the vastus lateralis muscle, determined by ultrasonography, showed no significant changes in either group. The PCSA decreased in NT by -7.8 (SD 0.8)% (P < 0.05) while in TR PCSA showed only an insignificant tendency to decrease [-3.8 (SD 3.8)%]. Changes in force were related more to changes in neural activation levels than to those in PCSA. The results suggest that reduction of muscle strength by BR is affected by a decreased ability to activate motor units, and that the exercise used in the present experiment is effective as a countermeasure.

本文言語English
ページ(範囲)7-12
ページ数6
ジャーナルEuropean Journal of Applied Physiology
84
1-2
DOI
出版ステータスPublished - 2001
外部発表はい

ASJC Scopus subject areas

  • 整形外科およびスポーツ医学
  • 公衆衛生学、環境および労働衛生
  • 生理学(医学)

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