Human growth hormone response to repeated bouts of aerobic exercise

J. A. Kanaley, J. Y. Weltman, J. D. Veldhuis, A. D. Rogol, M. L. Hartman, A. Weltman
1997 Journal of applied physiology  
Human growth hormone response to repeated bouts of aerobic exercise. J. Appl. Physiol. 83(5): 1756-1761, 1997.-We examined whether repeated bouts of exercise could override growth hormone (GH) auto-negative feedback. Seven moderately trained men were studied on three occasions: a control day (C), a sequential exercise day (SEB; at 1000, 1130, and 1300), and a delayed exercise day (DEB; at 1000, 1400, and 1800). The duration of each exercise bout was 30 min at 70% maximal O 2 consumption (V O 2
more » ... ax ) on a cycle ergometer. Standard meals were provided at 0600 and 2200. GH was measured every 5-10 min for 24 h (0800-0800). Daytime (0800-2200) integrated GH concentrations were ϳ150-160% greater during SEB and DEB than during C: 1,282 Ϯ 345, 3,192 Ϯ 669, and 3,389 Ϯ 991 min·µg·l Ϫ1 for C, SEB, and DEB, respectively [SEB Ͼ C (P Ͻ 0.06), DEB Ͼ C (P Ͻ 0.03)]. There were no differences in GH release during sleep (2300-0700). Deconvolution analysis revealed that the increase in 14-h integrated GH concentration on DEB was accounted for by an increase in the mass of GH secreted per pulse (per liter of distribution volume, l v ): 7.0 Ϯ 2.9 and 15.9 Ϯ 2.6 µg/l v for C and DEB, respectively (P Ͻ 0.01). Comparison of 1.5-h integrated GH concentrations on the SEB and DEB days (30 min exercise ϩ 60 min recovery) revealed that, with each subsequent exercise bout, GH release apparently increased progressively, with a slightly greater increase on the DEB day [SEB vs. DEB: 497 Ϯ 162 vs. 407 Ϯ 166 (bout 1), 566 Ϯ 152 vs. 854 Ϯ 184 (bout 2), and 633 Ϯ 149 vs. 1,030 Ϯ 352 min·µg·l Ϫ1 (bout 3), P Ͻ 0.05]. We conclude that the GH response to acute aerobic exercise is augmented with repeated bouts of exercise.
doi:10.1152/jappl.1997.83.5.1756 pmid:9375348 fatcat:kd7iblubknay5c5ysnsewy6esy