Exercise studies with elderly volunteers

Age and Ageing,  May, 1994  by C.A. Greig,  A. Young,  D.A. Skelton,  E. Pippet,  F.M.M. Butler,  S.M. Mahmud

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The practicalities of conducting exercise studies with elderly and very elderly people have not been well described. In order to help others plan and perform such studies we describe our experience of recruiting volunteers, applying selection criteria, measuring strength, power, cardiorespiratory responses, and potentially related functional abilities.

Exclusion criteria are offered, for safety and to characterize subjects as free of disease which might alter their exercise performance. International agreement on these, or similar, criteria would be valuable.

The budget must be adequate for prolonged recruitment before a study and for the liberal use of taxis during it.

With healthy subjects in their seventies, the coefficients of variation (CV) for repeated measurements of strength and power were: handgrip 3%, isometric knee extension 6%, isometric elbow flexion 6%, and lower limb extensor power 9%. CV for isometric knee extension by healthy subjects in their eighties was 4%. Treadmill ergometry is more time-consuming than with younger subjects. During progressive treadmill tests, the heart rate interpolated to oxygen consumptions of 10 and 15 ml.[kg.sub.-1].[min.sub.-1] had CV = 4% and 7%, respectively.

Regular physical activity has an important role in preventing disease (e.g. osteoporosis, coronary artery disease, non-insulin dependent diabetes mellitus), in reducing disability (e.g. angina, intermittent claudication, chronic airflow obstruction) and in enhancing mood and general well-being (1). It may also preserve the ability to perform functionally important everyday tasks (2) despite the progressive loss of muscle mass associated with old age (3)(4). Knowledge of exercise physiology in old age, however, is sketchy, especially beyond 75 years of age. This paper describes our experience of some of the difficulties presented by such studies, and potential solutions in respect of recruitment, selection, safety, and test protocols.

During the past 3 years, the Human Performance Laboratory (HPL) has recruited over 950 volunteers between the ages of 62 and 98 years. By May 1993, tests of muscle strength and explosive power and related tests of functional ability had been performed on 350 occasions by 249 volunteers aged 62-98 years (Table I) and 126 treadmill exercise tests and 90 self-paced corridor walking tests had been performed by 34 volunteers aged 65-84 years (Table II).

Table I. Tests of strength, power, and poetntially related functional abilities performed in the HPL, to May 1993 (189 women and 60 men; age range 62-98 years)

Age group       No. of       No. of
(years)         people       occasions
60-69            36           51
70-79           112          166
80-89            89          119
90 +             12           14
Total           249          350

Table II. Treadmill exercise tests and/or corridor walking tests performed in the HPL, to May 1993 (23 women and 11 men; age range 65-84)

Age group       No. of       No. of
(years)         people       occasions
60-69            4            17
70-79           22            91
80 +             8            40
Total           34           148

Recruitment of volunteers

This is an important and largely unpublicized issue. Recruitment is extremely time consuming, particularly when applying strict health criteria to people over 75. Not only is pathology common at that age but it has been suggested that healthy elderly people may be less inclined to volunteer for studies in a 'clinical' environment (5).

To attract healthy volunteers over 65 we published a prominent advertisement in a local newspaper and posters were displayed around the hospital, in local day centres, shops and luncheon clubs. The response was disappointing. A 'press release' was then sent to a selection of both national and local newspapers. This resulted in several published articles, often quoting our press release verbatim, and produced a large response. The majority of the potential volunteers now on the HPL's register were identified in this way.

Although newspaper articles have proved to be our most successful means of attracting volunteers, the proportion of volunteers who meet our selection criteria is low. For example, out of 225 responses to a recent article in a London daily newspaper, only 22 were suitable for inclusion in our studies. Of a total of 585 responses to one series of local and national newspaper articles, only 17% were suitable for inclusion.

One of our studies required volunteers aged over 75 who, although 'healthy' or 'medically stable' (see 'Selection of subjects', below), were sufficiently frail that they had chosen to live in warden-controlled accommodation. First, permission was obtained from local housing trusts providing such accommodation. The wardens then broached the subject with those they considered potential volunteers. Only then did the investigator approach the potential volunteers, in their homes and accompanied by the warden. It is hard to see how this slow process could have been accelerated without either taking advantage of the residents or antagonizing the management. Recruiting this type of subject remains a challenge.