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

Abstract

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. 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. This was a repeated-measures design in which each subject served as their own control. This study was conducted at the University of Virginia General Clinical Research Center. Subjects were healthy nonobese (n = 15) and obese (n = 14) young adults. 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. Twenty-four hour GH secretion was measured. 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. The present data suggest that continuous and intermittent exercise training should be comparably effective in increasing 24-h GH secretion.