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Responses of muscle mass, strength and gene transcripts to long-term heat stress in healthy human subjects.

Authors
  • Goto, Katsumasa
  • Oda, Hideshi
  • Kondo, Hidehiko
  • Igaki, Michihito
  • Suzuki, Atsushi
  • Tsuchiya, Shuichi
  • Murase, Takatoshi
  • Hase, Tadashi
  • Fujiya, Hiroto
  • Matsumoto, Ichiro
  • Naito, Hisashi
  • Sugiura, Takao
  • Ohira, Yoshinobu
  • Yoshioka, Toshitada
Type
Published Article
Journal
European Journal of Applied Physiology and Occupational Physiology
Publisher
Springer-Verlag
Publication Date
Jan 01, 2011
Volume
111
Issue
1
Pages
17–27
Identifiers
DOI: 10.1007/s00421-010-1617-1
PMID: 20803152
Source
Medline
License
Unknown

Abstract

The present study was performed to investigate the effects of long-term heat stress on mass, strength and gene expression profile of human skeletal muscles without exercise training. Eight healthy men were subjected to 10-week application of heat stress, which was performed for the quadriceps muscles for 8 h/day and 4 days/week by using a heat- and steam-generating sheet. Maximum isometric force during knee extension of the heated leg significantly increased after heat stress (~5.8%, P < 0.05). Mean cross-sectional areas (CSAs) of vastus lateralis (VL, ~2.7%) and rectus femoris (~6.1%) muscles, as well as fiber CSA (8.3%) in VL, in the heated leg were also significantly increased (P < 0.05). Statistical analysis of microarrays (SAM) revealed that 10 weeks of heat stress increased the transcript level of 925 genes and decreased that of 1,300 genes, and gene function clustering analysis (Database for Annotation, Visualization and Integrated Discovery: DAVID) showed that these regulated transcripts stemmed from diverse functional categories. Transcript level of ubiquinol-cytochrome c reductase binding protein (UQCRB) was significantly increased by 10 weeks of heat stress (~3.0 folds). UQCRB is classified as one of the oxidative phosphorylation-associated genes, suggesting that heat stress can stimulate ATP synthesis. These results suggested that long-term application of heat stress could be effective in increasing the muscle strength associated with hypertrophy without exercise training.

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