Effects of continuous versus intermittent exercise, obesity, and gender on growth hormone secretion

Context: Obesity attenuates spontaneous GH secretion and the GH response to exercise. Obese individuals often have low fitness levels, limiting their ability to complete a typical 30-min bout of continuous exercise. An alternative regimen in obese subjects may be shorter bouts of exercise interspersed throughout the day. Objective: The objective of the study was to examine whether intermittent and continuous exercise interventions evoke similar patterns of 24-h GH secretion and whether responses are attenuated in obese subjects or affected by gender. Design: This was a repeated-measures design in which each subject served as their own control. Setting: This study was conducted at the University of Virginia General Clinical Research Center. Subjects: Subjects were healthy nonobese (n = 15) and obese (n = 14) young adults. Interventions: Subjects were studied over 24 h at the General Clinical Research Center on three occasions: control, one 30-min bout of exercise, and three 10-min bouts of exercise. Main Outcome Measures: Twenty-four hour GH secretion was measured. Results: Compared with unstimulated 24-h GH secretion, both intermittent and continuous exercise, at constant exercise intensity, resulted in severalfold elevation of 24-h integrated serum GH concentrations in young adults. Basal and pulsatile modes of GH secretion were attenuated both at rest and during exercise in obese subjects. Conclusions: The present data suggest that continuous and intermittent exercise training should be comparably effective in increasing 24-h GH secretion.