Mitochondrial volume density in human skeletal muscle following heavy resistance training

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Abstract

MACDOUGALL, J. D., D. G. SALE, J. R. MOROZ, G. C. B. ELDER, J. R. SUTTON and H. HOWALD. Mitochondrial volume density in human skeletal muscle following heavy resistance training. Med Sci. Sports. Vol. 11, No. 2, pp. 164-166, 1979. Needle biopsies were taken from triceps brachii of 6 healthy males before and after a 6 month intensive weight training programme. The tissue was sectioned, photographed under a Philips EM200 and subjected to stereological analysis. Cross sectional fibre areas were also calculated from cryostat sections stained for ATPase activity. Morphometric analysis indicated that training resulted in a significant 26% reduction in mitochondrial volume density and a 25% reduction in the mitochondrial volume to myofibrillar volume ratio. These changes were accompanied by significant increases in fibre area for both FT (33%) and ST (27%) fibres as determined from the light microscope. There was a significant correlation between the reduction in mitochondrial volume density and the increase in FT fibre area following training (r = 0.845). It was concluded that heavy resistance training leads to a dilution of the mitochondrial volume density through an increase in myofibrillar size with hypertrophy.

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