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Titolo:
Changes in muscle size, architecture, and neural activation after 20 days of bed rest with and without resistance exercise
Autore:
Kawakami, Y; Akima, H; Kubo, K; Muraoka, Y; Hasegawa, H; Kouzaki, M; Imai, M; Suzuki, Y; Gunji, A; Kanehisa, H; Fukunaga, T;
Indirizzi:
Univ Tokyo, Dept Life Sci Sports Sci, Meguro Ku, Tokyo 1538902, Japan UnivTokyo Tokyo Japan 1538902 orts Sci, Meguro Ku, Tokyo 1538902, Japan Seigakuin Univ, Ageo, Saitama 3620053, Japan Seigakuin Univ Ageo Saitama Japan 3620053 v, Ageo, Saitama 3620053, Japan
Titolo Testata:
EUROPEAN JOURNAL OF APPLIED PHYSIOLOGY
fascicolo: 1-2, volume: 84, anno: 2001,
pagine: 7 - 12
SICI:
1439-6319(200101/02)84:1-2<7:CIMSAA>2.0.ZU;2-Z
Fonte:
ISI
Lingua:
ENG
Soggetto:
CROSS-SECTIONAL AREA; LOWER-LIMB; STRENGTH; ADAPTATIONS; PENNATION; TENSION; FLEXOR; HUMANS; MASS;
Keywords:
pennation angle; physiological cross-sectional area; twitch interpolation; countermeasure;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
32
Recensione:
Indirizzi per estratti:
Indirizzo: Kawakami, Y Univ Tokyo, Dept Life Sci Sports Sci, Meguro Ku, Komaba 3-8-1,Tokyo 1538902, Japan Univ Tokyo Komaba 3-8-1 Tokyo Japan 1538902 yo 1538902, Japan
Citazione:
Y. Kawakami et al., "Changes in muscle size, architecture, and neural activation after 20 days of bed rest with and without resistance exercise", EUR J A PHY, 84(1-2), 2001, pp. 7-12

Abstract

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, physiologicalcross-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 twogroups 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.

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Documento generato il 26/09/20 alle ore 05:06:16