Skelton, Dawn Alexandra; (1995) Strength, power and functional ability in healthy elderly people. Doctoral thesis (Ph.D.), University College London.

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Abstract

This thesis considers five major questions. 1) What are the age-related losses of strength, power and selected functional ability in healthy elderly people. 2) How strict do health criteria for "healthy" elderly people need to be. 3) Can exercise training improve strength and power in healthy elderly women. 4) Do isolated improvements in strength and power improve selected functional ability. and 6) Can "thresholds of strength and power for maintenance of functional ability" be identified in healthy elderly people. Reproducibility studies of measurements made on the "strength chair", Nottingham Leg Extensor Power Rig, questionnaires of social competence and physical activity and the selected functional tests showed good reliability on retest in elderly people. The health criteria used for describing "healthy" and "medically stable" elderly people and the methods used to recruit such people are discussed. 150 'healthy' and 'medically stable' men and women aged 65 to 89, meeting strict health criteria, were recruited for this cross-sectional study. Isometric strength, leg extensor power and functional ability tests (rising from a chair and from the floor, lifting a weighted bag and stepping ability) were measured. Differences in strength and power over the age range imply a loss of 1-2% and 31/2% per annum respectively, even in health. The decline of explosive power was greater than the decline of knee extensor strength in men (p=0.0001) but not significantly so in women (p=0.08). Healthy elderly men and women have little difficulty in lifting a weighted bag or rising from a low chair. Healthy men have little difficulty in rising from the kneeling position or stepping up but 19% of women aged over 75 were unable to rise from the kneeling position and 60% of the 75-79's and 100% of the 80-89 year old women were unable to step 50cm. Chair rise time, kneel rise time and step up height correlated with explosive power and knee extensor strength standardised for body weight and with age. Kneel rise time and step up height correlated with habitual physical activity (p=-0.26 and 0.34 respectively). Medically stable women were weaker and less powerful per kg body weight than their healthy counterparts and so the healthy criteria are necessary to differentiate between healthy ageing and ageing effects compounded by disease. "Standard" values of strength, power and selected functional ability in healthy old age have been presented and compared to a group of hip fracture patients. Forty healthy and medically stable women aged ? 75 years, took part in a 12 week controlled, randomised study of progressive resistance strength-training. There were training induced improvements in isometric knee extensor, elbow flexor and handgrip strength (mean 4-27%), power/kg (mean 18%), step height (2.5cm) and time to rise from the floor (-21%). However, ten out of twelve functional tasks did not improve. There were no changes in weight, arm muscle circumference (skinfolds), body density, total body water or phase angle (body impedance analysis). At follow up, six months later, those who had continued in an exercise class had maintained their strength improvements better than those who had not taken part in an exercise class. Distinct values of strength or power necessary for maintenance of functional ability could not be identified by simple correlation analysis, comparison of strength and power of those able or unable to perform a given task or short term increases in strength and power or decreases in power to facilitate the crossing of a functionally important threshold. Instead there appears to be "threshold zones". These "threshold zones" facilitate selective targeting of people in need of interventions to improve strength or power.

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