Dynamics of GH secretion during incremental exercise in obesity, before and after a short period of training at different work-loads

Alberto Salvadori (1) , Paolo Fanari (2) , Paolo Marzullo (3) , Franco Codecasa (1) , Ilaria Tovaglieri (1) , Mauro Cornacchia (1) , Gillian E Walker (4) , Amelia Brunani (5) , Erminio Longhini (1)

1 Respiratory Rehabilitation
2 Respiratory Rehabilitation
3 Dep. Of Clinical and Experimental Medicine
4 Chemical Laboratory
5 Rehabilitation Medicine

Background. Growth hormone (GH) is normally sensitive to physical exercise. Intensity and duration of exercise, fitness as well as age, all can influence GH response to exercise. In obesity, GH secretion is decreased both in basal conditions and in response to exercise. Objective. To analyse the dynamics of GH response to a progressive cycloergometric test conducted up to exhaustion in adult normal subjects and obese patients, after a reconditioning program at different workloads. Design and methods. We studied 8 lean subjects (4 males, mean age 34.3 yrs, range 26-47 yrs, mean BMI 22.1 kg/m²). GH was sampled at baseline and during the last 30 s of each power output increase. Anaerobic threshold (AT) was detected by the V-slope method. The same test was carried out in 16 obese subjects (7 males, mean age 39.1 yrs, range 20-59 yrs, mean BMI 35.8 kg/m²) and repeated after a 4-week reconditioning program consisting of aerobic workout (Group A, 8 subjects, 3 males, mean age 40.5 yrs, range 22-59 yrs, mean BMI 33.6 kg/m²), and aerobic plus anaerobic work (group B, 8 subjects, 4 males, mean age 37.6 yrs, range 20-56 yrs, mean BMI 38.0 kg/m²) for 6 days/wk, with no dietary restrictions. Results. Mean exercise peak occurred at higher intensity in controls (140 vs. 110 W, p<0.05) and AT exceeded at higher work outputs than in obese subjects (102 vs. 74 W, p<0.05). In controls, GH response to exercise was prompt and further sustained after AT; in obese subjects, GH increased slowly and unsignificantly before AT, thereafter it increased to lower levels than in controls (p<0.001). Following the reconditioning period, both Group A and Group B of obese subjects failed to improve exercise performance as well as GH response to exercise before AT; beyond AT, a greater GH response to exercise occurred in Group B than Group A (7.59 ± 0.32 μg/l at peak of exercise) with significantly different Delta AUCs following AT: 30.5 ± 12 μg-min/l in the Group A vs 124.2 ± 38 μg-min/l in the Group B, p < 0.05. Conclusions. Our results confirm the blunted GH response to exercise in obese adults when compared to lean counterparts. With obesity, aerobic training poorly increases the GH response beyond AT while supplemental anaerobic workload appears to increase GH response beyond AT. These observations may have implications for prescription of physical exercise, which is one of the recommendations in the management of obesity.

Mots clés: Medicine

Alberto Salvadori, Paolo Fanari, Paolo Marzullo, Franco Codecasa, Ilaria Tovaglieri, et al.. Dynamics of GH secretion during incremental exercise in obesity, before and after a short period of training at different work-loads. Clinical Endocrinology, 2010, ⟨10.1111/j.1365-2265.2010.03837.x⟩. ⟨hal-00552613⟩