Effect of physical training on age-related reduction of GH secretion during exercise in normally cycling women.

OBJECTIVE To evaluate whether prolonged physical activity (25 km/week running for 8 years) modifies GH decline. DESIGN: The GH response to maximal exercise on bicycle-ergometer was tested in younger (26-30 years) and older (42-46 years) healthy women. Each age group included 2 subgroups of 10 sedentary and 10 runners, which were compared. The workload was increased at 3 min intervals from time 0 until exhaustion. Subjects with a low maximal capacity (as established in a preliminary test) pedalled for 3-4 min against no workload at the beginning of the test, so that exercises lasted about 15 min in all individuals. RESULTS: At exhaustion, heart rate and systolic pressure were significantly higher in sedentary than in trained subjects, whereas V(O(2)max), blood glucose and plasma lactate levels were similar in all groups. Exercise induced similar GH responses in younger sedentary and exercise-trained subjects and in older exercise-trained subjects, with mean peak levels 7.5 times higher than baseline. In contrast, in older sedentary women peak GH level was only 4.4 times higher than baseline and was significantly lower than in the other groups. CONCLUSION: These data suggest that in women prolonged physical training exerts protective effects against age-dependent decline in GH secretion.