| Summary: | 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.
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