Endocrine Abstracts

Exercise is a potent stimulus for growth hormone (GH) release and a single 30 s sprint elicits a marked increase in circulating GH. However, the mechanisms regulating GH release during and after exercise are not fully understood (1). The aim of the present study was to determine whether age, body composition, the metabolic response to or performance during a single 30 s sprint are predictors of the GH response in young men.

Following local Ethics Committee approval, twenty-seven healthy, non-obese (mean body mass index (BMI) plus/minus SD; 24.9 ± 2.0 kg/m²) males aged 18-32 years (24.1 plus/minus 3.6 years) were familiarised with the exercise protocol. Subjects then arrived at the laboratory following an overnight fast and performed an all-out 30 s sprint on a cycle ergometer. Blood samples were taken via a venous cannula at rest, post-warm-up and 5, 10, 20, 30, 40 and 60 min after the sprint. Univariate linear regression analysis was employed to evaluate age-, BMI-, performance- and metabolic-dependent changes from pre-exercise to peak GH and integrated GH for 60 min after the sprint.

Growth hormone was elevated following the sprint (change in GH, 17.0 plus/minus 14.2 micrograms per litre; integrated GH, 662 plus/minus 582 micrograms per litre). Performance characteristics (work done, peak power, pedal rate), the metabolic response to exercise (blood lactate, plasma ammonia, blood pH) and BMI were not significant predictors of the GH response to exercise. However, age emerged as a significant predictor of both integrated GH (beta = -0.547, p = 0.003) and change in GH (beta = -0.448, p = 0.019) after the sprint.

In conclusion, age appears to affect the GH response to sprint exercise in young men.

(1) Stokes, K (2003) Growth Horm IGF Res 13:225-238