Servicio de Información Comunitario sobre Investigación y Desarrollo - CORDIS

Does muscle unsteadiness and asymmetry contribute to frailty and can they be improved by appropriate training

Data were collected on healthy young and older people. The third group studied were an age-matched group of older people who fell for medically unexplained reasons.

Maximal voluntary strength was tested in the quadriceps, hamstrings, dorsi- and plantar- flexors at a range of a) knee angles for isometric contractions and also b) angular velocities for concentric and eccentric contractions.

During isometric contractions the older subjects were significantly weaker than the younger group in all cases. The length:tension relationship was similar in these two groups, indicating that the muscle/tendon complex remains essentially the same length. The fallers were generally weaker than the age-matched non-fallers and this was particularly obvious in the knee muscles at shorter lengths.

During dynamic contractions the older group had better preserved eccentric force generation than either isometric or concentric and in general, dynamic force generation was better preserved at higher angular velocities. The older fallers generally produced similar dynamic forces to the older non-fallers, except for the plantar-flexors where the fallers were weaker.

Voluntary activation in the quadriceps was similar in the two age groups and also in the elderly fallers.

Co-contraction of antagonist muscles during isometric and dynamic maximal voluntary contractions was similar in the two age groups. The fallers had higher levels of co-activation in the plantar flexors during eccentric dorsiflexion, otherwise there was no difference between them and the non-fallers.

Intrinsic force of the quadriceps as measured by ultrasonography of the anatomical cross sectional area was similar in both age groups. The fallers had a lower intrinsic force than the non fallers in all contraction types, but this did not reach statistical significance.

Leg extension power output was significantly less in the older subjects while the ratio of isometric strength: power was similar in the two age groups. It was similar in the two older groups.

Asymmetry of strength tended to be slightly greater in the older subjects, but there were generally no significant differences between older and younger people. It was similar in the fallers and non-fallers. Asymmetry of power was similar in all three groups. Greater asymmetry of isometric strength was found at some, but not all, joint angles in the hamstrings and dorsiflexors of the fallers and during slow eccentric contractions.

Correlations between strength, power and the number of falls. Reduced strength and power were strongly associated with falling.

Steadiness was measured during isometric, ansiometric & functional activities (stepping up and down, standing up and sitting down. During isometric and eccentric ansiometric contractions the older subjects tended to be less steady than the young and the fallers were less steady than the non fallers. During functional activities the older subjects were less steady, but there were no differences between fallers and non-fallers. In the fallers steadiness was particularly reduced during eccentric contractions.

Training. Elderly fallers and non-fallers responded similarly to a one year training programme. This resulted in significant increases in strength of the quadriceps and hamstrings muscles (but not the dorsi-or plantar- flexors), power output and power symmetry. It had no effect on steadiness during isometric, ansiometric or functional activities or strength symmetry.

The inclusion of a 10 minute period of Tai Chi in the supervised programme did not affect the results in any way.

These results suggest that of the muscle measurements made, reduced strength and power output are the most important factors associated with falling in older people, along with reduced steadiness. Most of the measurements of muscle function revealed clear differences between young and older people and, although age matched, the fallers appeared to show greater changes than their chronological age would suggest.

Increased asymmetry of strength or power did not seem to identify fallers as has previously been suggested.

Fallers demonstrated a training response that was the same as that seen in people of a similar age who did not fall and therefore training should be effective in reducing the risk of falling. The inclusion of a short period of Tai Chi in the training sessions was not associated with any increased physiological benefit, although it may be effective in improving confidence and habitual levels of physical activity.

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Guy's Campus
United Kingdom
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