CAPILLARIZATION AND FIBER TYPES IN HYPERTROPHIED M-PLANTARIS IN RATS OF VARIOUS AGES

Influences of age, overload obtained through denervation of synergists , and training on the capillarisation of the m. plantaris were compare d in 5-, 13- and 25-month-old rats in relation to different fibre type s. Overload resulted in about 30%. hypertrophy in each age group. Age effects were significant only in the deep (more oxidative) region of t he muscle. From 5 to 13 months, the percentage of FOG fibres increased at the expense of FG fibres, while the fibre cross-sectional areas (F CSA) of each fibre type increased. From 13 to 25 months, the FCSA of F G fibres decreased, as did the local capillary-to-fibre ratio (LCFR) o f each fibre type, indicating capillary loss and a declined capillary density for each fibre type (CFD). Overload effects were identical for both the superficial (more glycolytic) and the deep region for each a ge group. With overload, FCSA and LCFR of each fibre type increased, w hile CFD decreased, indicating that capillary proliferation occurred w ith overload, even at old age, although lagging behind increases in FC SAs. Training showed minor effects.