Wspólnotowy Serwis Informacyjny Badan i Rozwoju - CORDIS

Muscle weakness and reduced locomotory function in frailty

This study aimed at investigating the alterations in muscle architecture and in tendon mechanical properties associated with old age, their impact on muscle and locomotory function, and their reversal/mitigation in response to a 12-month physical activity programme.

The study was performed on 58 older individuals (28 males, 30 females) and compared to those obtained on 31 younger adults (15 males, 16 females). The results obtained showed that sarcopenia is associated with a reduction in fibre fascicle length and pennation angle of the plantarflexor muscles and with lower tendon stiffness in older individuals. Neural drive to the muscle was also different from that of young adults since muscle voluntary activation was found to be lower in the older individuals. The combined effect of these changes accounted for about 50% of the loss in peak muscle power and 70% of the loss in isometric strength, indicating a deterioration in muscle quality in old age.

The lower tendon stiffness in the elderly was also reflected by a different behaviour of the fibre fascicles and the tendon throughout the walking cycle: in the older individuals, fascicle length remained more or less constant while the tendon underwent considerable stretch, whereas in the young, greater fascicle and lower tendon length changes were observed.

This different behaviour of the muscle-tendon complex of the older individuals was associated with an increased metabolic cost of walking and with a greater antagonist muscle co-activation. In response to the 12-month physical activity programme, a significant reversal of these age-related changes was found since,
- Muscle cross-sectional area and volume were larger,
- Fascicle length and pennation angle increased,
- Tendon stiffness increased,
- Voluntary activation was greater,
- Both absolute and relative (normalised for muscle CSA and volume) peak isometric force and power increased.

Although these adaptations had no effect on the metabolic cost of walking (probably because of insufficient intensity of the aerobic component in the training), these were associated with an improvement in functional performance (6 min walk test, get up and go, one-leg standing balance). These findings indicate that muscle weakness in old age is not only due to a loss of muscle mass (sarcopenia) but also to alterations in the internal architecture of skeletal muscle compounded by a deterioration in tendon stiffness and by changes in neural drive which have repercussions on the metabolic cost of locomotion.

However, physical activity based on aerobic, concentric/eccentric strength and proprioceptive exercises performed at least twice per week, proves effective in reversing/mitigating most these age-related changes, resulting in improved muscle quantity, quality and functional performance. Since the strength training protocol used in this study involved several eccentric exercises, it is believed that the muscle stretch caused by this type of contraction provides an important stimulus for restoring muscle mass and fibre fascicle length. Hence it is recommended that future training programmes designed for older individuals should implement eccentric loading in their protocol including, also, aerobic and proprioceptive exercises.

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Reported by

Manchester Metropolitan University
Institute for Biophysical and Clinical Research into Human Movement, Alsager Campus, Hassall Road
ST7 2HL Alsager
United Kingdom
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