Nonuniform muscle hypertrophy: Its relation to muscle activation in training session

Taku Wakahara, Atsuki Fukutani, Yasuo Kawakami, Toshimasa Yanai

研究成果: Article査読

71 被引用数 (Scopus)

抄録

PURPOSE: Muscle hypertrophy in response to resistance training has been reported to occur nonuniformly along the length of the muscle. The purpose of the present study was to examine whether the regional difference in muscle hypertrophy induced by a training intervention corresponds to the regional difference in muscle activation in the training session. METHODS: Twelve young men participated in a training intervention program for the elbow extensors with a multijoint resistance exercise for 12 wk (3 d·wk). Before and after the intervention, cross-sectional areas of the triceps brachii along its length were measured with magnetic resonance images. A series of transverse relaxation time (T2)-weighted magnetic resonance images was recorded before and immediately after the first session of training intervention. The T2 was calculated for each pixel within the triceps brachii. In the images recorded after the session, the number of pixels with a T2 greater than the threshold (mean + 1 SD of T2 before the session) was expressed as the ratio to the whole number of pixels within the muscle and used as an index of muscle activation (percent activated area). RESULTS: The percent activated area of the triceps brachii in the first session was significantly higher in the middle regions than that in the most proximal region. Similarly, the relative change in cross-sectional area induced by the training intervention was also significantly greater in the middle regions than the most proximal region. CONCLUSION: The results suggest that nonuniform muscle hypertrophy after training intervention is due to the region-specific muscle activation during the training session.

本文言語English
ページ(範囲)2158-2165
ページ数8
ジャーナルMedicine and Science in Sports and Exercise
45
11
DOI
出版ステータスPublished - 2013 11

ASJC Scopus subject areas

  • 整形外科およびスポーツ医学
  • 理学療法、スポーツ療法とリハビリテーション

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