EFFECT OF A SUSTAINED PROGRAM OF RESISTANCE TRAINING ON THE ACUTE GROWTH-HORMONE RESPONSE TO RESISTANCE EXERCISE IN OLDER ADULTS

We have previously shown that an episode of resistance exercise provokes an acute rise in circulating growth hormone (GH), and that this rise is severely blunted in older men and women. To determine whether this impairment simply reflects the decreased physical fitness of older people, we studied the effects of long-term resistance training on circulating levels of GH and insulin-like growth factor I (IGF-I) and on the acute GH response to exercise in 5 men and 9 women, aged 69.6 +/- 1.1 yrs (SEM). Subjects were randomly assigned to either an exercise program, consisting of 12 weight-lifting exercises (3 sets of 8 repetitions, 3 times each week) or to a control group. After testing maximum baseline strength by the 1 RM method subjects returned to the laboratory for assessment of basal GH and IGF-I levels and the GH response to exercise. Venous blood was drawn at baseline, after each of 12 exercises (3 sets of 8 repetitions at 85% 1 RM), and every 2 minutes into the first 10 minutes of recovery. The exercise circuit with blood sampling was repeated at 15, 30 and 52 weeks for both groups. Basal GH and IGF-I values did not change in either group throughout the training period nor did the GH secretory response to exercise. Three exercisers had a peak GH concentration greater than 8 mu g/l after 30 weeks of training, although only one of these showed a significant increase (29 mu g/l) after 52 weeks. We conclude that a sustained program of moderate intensity resistance training does not repair age-related deficits in circulating levels of growth hormone or IGF-I, either at rest or following an acute exercise stimulus.