Table 3.
Distribution of skeletal muscle fibre type and oxidative capacity
| Variable | Assessment | Effect of training | |||||
|---|---|---|---|---|---|---|---|
| LI group | HI group | ||||||
| Baseline | 2 months | 6 months | Baseline | 2 months | 6 months | ||
| Skeletal muscle fibre distribution (% CSA) | |||||||
| Type 1 muscle fibre | 49.3 ± 1.9 | 50.2 ± 2.1 | 52.2 ± 2.6 | 49.3 ± 1.6 | 49.7 ± 1.9 | 49.7 ± 1.9 | |
| Type 2a muscle fibre | 44.5 ± 1.7 | 42.9 ± 1.9 | 41.8 ± 2.2 | 44.0 ± 1.4 | 42.9 ± 1.9 | 41.8 ± 2.2 | |
| Type 2x muscle fibre | 6.2 ± 0.9 | 6.9 ± 0.8 | 6.0 ± 0.7 | 6.7 ± 1.0 | 7.9 ± 1.0 | 8.5 ± 1.1 | |
| Oxidative enzyme activity (µmol [g wet weight]−1 min−1) | |||||||
| Succinate dehydrogenase | 13.3 ± 0.4 | 12.7 ± 0.3 | 12.8 ± 0.3 | 13.7 ± 0.4 | 12.9 ± 0.4 | 14.3 ± 0.5 | |
| Cytochrome c oxidase | 5.2 ± 0.6 | 6.0 ± 0.7 | 7.4 ± 0.9 | 4.5 ± 0.4 | 5.8 ± 0.6 | 6.5 ± 0.7 | <0.01 |
| Citrate synthase | 9.5 ± 0.9 | 11.1 ± 1.3 | 12.9 ± 1.1 | 10.2 ± 0.9 | 9.9 ± 0.9 | 11.9 ± 0.9 | <0.01 |
| β-Hydroxyacyl-CoA dehydrogenase | 4.8 ± 0.7 | 5.7 ± 0.8 | 6.4 ± 0.7 | 5.6 ± 0.6 | 4.9 ± 0.6 | 6.1 ± 0.7 | |
Data are means ± SEM
CSA, fibre cross-sectional area