J Appl Physiol Articles in PresS. Published on February 8, 2002 as DOI 10.1152/japplphysiol.01018.2001
Final Revision 10/24/01 GENDER GOVERNS THE RELATIONSHIP BETWEEN EXERCISE INTENSITY AND GROWTH HORMONE (GH) RELEASE IN YOUNG ADULTS Cathy J Pritzlaff-Roy1 Laurie Widemen2 Judy Y Weltman2 Rob Abbott3 Margaret Gutgesell1 Mark L Hartman2 Johannes D Veldhuis2 Arthur Weltman1,2 Departments of Human Services 1, Medicine 2, and Health Evaluation Sciences 3 General Clinical Research Center University of Virginia
Running Title: Gender, exercise intensity and GH release
Correspondence should be directed to: Arthur Weltman, Ph.D. Exercise Physiology Laboratory / Memorial Gym University of Virginia Charlottesville, VA 22903 (434) 924-6191 (434) 924-1389 (fax)
[email protected] (e-mail)
Copyright 2002 by the American Physiological Society.
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ABSTRACT We previously reported that in young adult males GH release is related to exercise intensity in a linear dose-response manner (Pritzlaff et al. J Appl Physiol 87: 498-504, 1999). To investigate the effects of gender and exercise intensity on growth hormone (GH) release, 8 women (age = 24.3 + 1.3 yr, ht = 171 + 3.2 cm, wt = 63.6 + 8.7 kg) were each tested on 6 randomly ordered occasions [1 control condition (C), 5 exercise conditions (Ex)]. Serum GH concentrations were measured in samples obtained at 10-min intervals between 0700h and 0900h (baseline) and 0900h and 1300h (exercise + recovery or control). Integrated GH concentrations (IGHC) were calculated by trapezoidal reconstruction. During Ex subjects exercised for 30 min (0900-0930h) at one of the following intensities [normalized to the lactate threshold (LT)]: 25 and 75% of the difference between LT and rest (0.25LT and 0.75LT, respectively), at LT, and at 25 and 75% of the difference between LT and VO2 peak (1.25LT and 1.75LT, respectively). No differences were observed among conditions for baseline IGHC. To determine if total (Ex + recovery) IGHC changed with increasing exercise intensity, the slopes associated with individual linear regression models were subjected to a Wilcoxon signed-rank test. To test for gender differences the present data in women were compared to the aforementioned previously published data in men. A Wilcoxon ranked-sums two-tailed test was used to analyze the slopes and intercepts from the regression models. Total IGHC [men: C = 250 + 60; 0.25LT = 203 + 69; 0.75LT = 448 + 125; LT = 452 + 119; 1.25LT = 512 + 121; 1.75LT = 713 + 115 µg.l-1.min-1) and women: C = 509 + 126; 0.25LT = 799 + 131; 0.75LT = 1013 + 219; LT = 764 + 97; 1.25LT = 954 + 186; 1.75LT = 1459 +253 µg.L1.min-1)] increased linearly with increasing exercise intensity (P
