אימונים Relationship between performance at different exercise intensities and skeletal muscl

[Mike Bikov]

J Appl Physiol. 2011 Mar 24. [Epub ahead of print]
Relationship between performance at different exercise intensities and skeletal muscle characteristics.

Iaia FM, Perez-Gomez J, Thomassen M, Nordsborg NB, Hellsten Y, Bangsbo J.

1University of Copenhagen.
Abstract

The hypothesis investigated whether exercise performance over a broad range of intensities is determined by specific skeletal muscle characteristics. Seven subjects performed 8-10 exhaustive cycle trials at different work loads ranging from 150 to 700 W (150 min - 20 s). No relationships between the performance times at high and low work loads were observed. A relationship (P<0.05) was observed between the percentage of FTx fibers and the exercise time at 579±21 W (~30 s; r(2)=0.88). Capillary-to-fibre-ratio (r(2): 0.58-0.85) was related (P<0.05) to exercise time at work intensities ranging from 395 to 270 W (2.5-21 min). Capillary density was correlated (r(2)=0.68; P<0.05) with the net rate of plasma K(+) accumulation during a ~3-min bout, and was estimated to explain 50 to 80% (P<0.05) of the total variance observed in exercise performances lasting approximately 30 s -3 min. The Na(+),K(+) pump β1 subunit expression was found to account for 13-34% (P<0.05) during exhaustive exercise of approximately 1-4 min. In conclusion, exercise performance at different intensities is related to specific physiological variables. A large distribution of FTx fibres may play a role during very intense efforts, i.e. ~30 s. Muscle capillaries and the Na(+),K(+) pump β1 subunit seem to be important determinants for performance during exhaustive high-intensity exercises lasting between 30 s to 4 min.​

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