Effects of strength training and immobilization on human muscle fibres.
Seven healthy male subjects were studied under control conditions and following 5-6 months of heavy resistance training and 5-6 weeks of immobilization in elbow casts. Cross-sectional fibre areas and nuclei-to-fibre ratios were calculated from cryostat sections of needle biopsies taken from triceps brachii. Training resulted in a 98% increase in maximal elbow extension strength as measured by a Cybex dynamometer, while immobilization resulted in a 41% decrease in strength. Both fast twitch (FT) and slow twitch (ST) fibre areas increased significantly with training by 39% and 31%, respectively. Immobilization resulted in significant decreases in fibre area by 33% for FT and 25% for ST fibres. The observed nuclei-to-fibre ratio was 10% greater following the training programme. However, this change was non-significant. There was also a non-significant correlation between the magnitude of the changes in fibre size and the changes in maximal strength following either training or immobilization.
D000328:Adult; D001284:Atrophy; D002467:Cell Nucleus / Q000473:pathology; D006801:Humans; D007103:Immobilization; D008297:Male; D009132:Muscles / Q000473:pathology*; D010806:Physical Education and Training; D013178:Sports Medicine; D014891:Weight Lifting