Effects of training on fibre composition in rat gastrocnemius muscle.
Forty-eight adult Wistar rats were divided into four groups for experimentation. The group I was used as a control and groups II, III and IV underwent progressive treadmill training. Samples of the red and mixed portions of m. gastrocnemius (lateral head) were stained with the histochemical technique of m-ATPase to determine the percentage of type I, IIA and IIB fibres, and with NADH-TR, in order to quantify variations in "low-oxidative" fibre percentages. The results showed that progressive training did not lead to statistical variations in the percentage of type I fibres. However, the proportion of type IIA fibres rose, while that of IIB fibres fell, in both cases significantly. Variations were more marked in mixed than in red Gastrocnemius muscle. A clear decrease was noted in "low-oxidative" fibres, which were virtually absent from red portion. This decrease was more marked, and occurred more rapidly, than in type IIB fibres.
Morales-Lopez
J L
JL
Department of Comparative Anatomy and Pathological Anatomy, Faculty of Veterinary Sciences, University of Cordoba, Spain.
Agüera
E
E
Miro
F
F
Galisteo
A M
AM
D000818:Animals; D005260:Female; D008297:Male; D009132:Muscles / Q000737:chemistry / Q000166:cytology / Q000502:physiology*; D010805:Physical Conditioning, Animal; D051381:Rats; D011919:Rats, Inbred Strains