Muscle fibre adaptations, strength and power development during strength and/or endurance training in 40 to 65-yr-old women

Abstract

The purpose of the present study was to examine muscle fibre composition and fibre size adaptations following 6 months of resistance and endurance training in 40 to 65-yr-old women (mean age 52 ±7 yr), and the changes in neuromuscular performance. The experimental groups were composed of strength training (S) group (n =27), endurance training (E) group (n = 27), concurrent S and E (C) group (n = 25) and control group (n = 20).

Maximal concentric and isometric strength showed similar significant increases in the S (9.8 and 18.4%, p < 0.001) and C (12.1 and 21.0%, p < 0.001) groups with slight increases in E (1.9 and 8.8%, p < 0.05). Maximal power increased to a similar extent in S (9.9%, p < 0.01) and C (12.5%, p < 0.001), however, the E and control groups showed significant decreases in power (-3.5 and -6.1%, respectively, p < 0.05). All training groups decreased their type IIB myofibre content and type IIA percentage increased significantly in the S group. Muscle fibre size remained statistically unaltered in S and C for each muscle fibre subtype, whereas the size of type IIA and type I showed a significant increase in the E and control groups, respectively.

The present data in middle-aged women showed that the S and C groups expressed similar neuromuscular adaptations in all variables measured. However, the selected differences observed by the correlations between type IIA muscle fibre adaptations and the changes in strength in the S and C groups suggested somewhat dissimilar mechanisms of adaptation, when training S alone or S concurrently with E.