Letters

Fitness for older people

Perhaps less well recognised are some of the other improvements seen in older people after exercise training. The ventilation threshold - the point at which anaerobic metabolism begins to augment aerobic metabolism during exercise - rises as a percentage of maximum oxygen consumption with age.² Yet critical power - the highest sustainable workload as a percentage of maximum workload - in trained older people is similar to that in young people.³ Healthy older people are therefore capable of prolonged sub-maximal "work." The dynamic responses in oxygen uptake, carbon dioxide exchange, ventilation, and heart rate at the onset of exercise slow with inactivity and aging.⁴ In exercise trained older people the kinetics of these responses accelerate and approach those of younger trained people.⁴ Similarly, I have shown that the kinetics of the ventilatory response to hypoxia are faster in trained than sedentary older people (unpublished MD thesis).

The approach to exercise training for older people in Britain is quite different from that which I have seen in Canada, reflecting the demands and expectations of North American practice, the greater availability of suitable facilities, and the greater interest shown by the retired population. There, in contrast with the rather informal procedure in Britain, entrants to exercise training programmes undergo a medical examination and supervised treadmill exercise to a functional maximum to identify factors of importance during exercise - for example, critical coronary artery disease. This permits the calculation of an effective and safe personal training heart rate, within the training sensitive zone, from the person's maximum heart and work rates. The use of target heart rates during exercise training in older people does not seem to be common in Britain but would be advantageous in monitoring the intensity of exercise, as a guide to increments in the intensity of training, and for safety. Which practice is thought correct or appropriate will depend on the country of practice, target intensity of exercise, and subject's risk factors.

W D F Smith 

Health Care for the Elderly, Derriford Hospital, Plymouth PL6 8HD .

1. Young A, Dinan S. Fitness for older people. BMJ 1994;309:331- 4. (30 July.) [Free Full Text]
2. Thomas SG, Cunningham DA, Thompson J, Rechnitzer PA. Exercise training and ventilation threshold in elderly. J Appl Physiol 1985;59:1472-6. [Abstract/Free Full Text]
3. Overend T, Cunningham DA, Paterson DH, Smith WDF. Physiological responses of young and elderly men to prolonged exercise at critical power. Eur J Appl Physiol 1992;64:187-93.
4. Paterson DH, Cunningham DA, Babcock MA. Oxygen kinetics in the elderly. In: Swanson GD, Grodins FS, Hughson RL, eds. Respiratory control. New York: Plenum, 1989:171-8.