Influence of acute and chronic exercise on insulin-like growth factor-I in healthy active elderly men and women

We examined the influence of physical activity (PA) and acute resistance exercise on insulin-like growth factor I (IGF-I) in 39 healthy, independent, community-dwelling elderly volunteers (14 men and 25 women) aged from 66 to 84. In a longitudinal non-interventional study, we compared the fluctuations in IGF-I levels and changes in habitual PA over a 6-month period. PA was evaluated by a questionnaire QAPSE (Questionnaire d’Activité Physique Saint-Etienne), and expressed by two activity indices: mean habitual daily energy expenditure (MHDEE), and daily energy expenditure corresponding to leisure time sports activities (sports activity index). In an experimental design we compared IGF-I levels before, at 1 and 15 minutes after short quadriceps muscle exertion (10 consecutive repetitions) carried out with optimal muscle power development. Changes in IGF-I levels over a 6-month period were positively related to changes in MHDEE (r=0.41; p<0.01), and sports activity (r=0.40; p<0.02). When analyzed by gender, these correlations were still statistically significant in women (r=0.39; p=0.05 and r=0.41; p<0.05), but not in men (r=0.36; p=0.21 and r=0.20; p=0.50). No changes (p=0.17) were observed in serum IGF-I concentrations after the acute exercise protocol. These findings indicate that IGF-I levels are positively related to fluctuations in habitual PA, at least in women. Further research is needed to establish the best intensity and duration of exercise training to induce these changes.