Endocrine Abstracts

Objective

There is large inter-individual variation in the growth hormone (GH) response to resistance exercise, but the intra-individual variation is unknown. This study aimed to determine the reproducibility of the GH response to a 30-min resistance exercise session.

Design

Following local Ethics Committee approval, nine male participants were familiarised before completing three trials in a random order. During two trials participants completed a resistance exercise bout followed by 60-min of recovery. In the other trial participants rested in the laboratory. Blood samples were taken at regular intervals during each trial.

Results

There was no significant difference in the mean (SD) weight that was lifted [98.4(21.3) vs. 98.9(20.1) kg], lactate response [2.5(0.9) vs. 2.50(0.9) mmol.l⁻¹] or HR [120(11) vs. 120(13) bpm] between the two exercise trials. Exercise elicited a significant increase in GH when compared to rest, with peak GH of 10.8(8.9), 6.6(6.6) and 1.3(2.4) μg l⁻¹ and GH area under the curve (AUC) of 550(540), 302(383) and 43(72) μg l⁻¹ for exercise trials 1 and 2, and the rest trial, respectively. Re-test correlation was significant for both peak GH concentrations (r=0.92, P<0.01) and GH AUC (r=0.88, P<0.05). Within-subject error for the exercise trials (change in mean + typical error) of peak GH and GH AUC was -4.3+2.4μg l⁻¹ and −248+194 μg l⁻¹, respectively. Within-subject percentage error (percentage change in mean + typical percentage error) for peak GH and GH AUC was 55+27% and 54+58%, respectively.

Conclusion

Despite reproducible exercise performance, systematic error is evident in both peak GH and GH AUC, indicating that further familiarisation may be required. Random error for peak GH is similar to that seen in response to other types of exercise.