Acute Human Growth Hormone Response in Elite Rowers After 12- weeks of Training

Abstract

2084 PURPOSE: A number of studies have examined the hGH response to a chronic exercise stimulus. Under a varying range of circumstances with sub-elite populations results have been mixed, with findings of an increase, decrease and no change being demonstrated. However, no studies exist which compare the exercise induced hGH response (EIGR) in elite rowers before and after a period of concentrated endurance training. The present study compared the acute hGH response to a standardised graded exercise stimulus in members of the GB heavyweight male rowing squad. METHODS: Eight elite male rowers entered the study. All have a minimum of six years international competitive experience, and all are Olympic gold medallists. Participants completed an incremental rowing exercise test in January and again in April. This comprised 5 × 4-minute stages (25 W/stage increment) and a sixth and final 4-minute effort which was a maximal paced effort. Capillary (earlobe) blood samples for lactate and hGH determination were taken at t = −10, 4, 8.5, 13, 17.5, 22, 28.5, 38.5, 48.5 and 58.5 minutes. O2, HR and power output were measured continuously throughout exercise. During 12-weeks training, 80% of weekly hours comprised aerobic work and 20% was a combination of strength training, lactate threshold (LT) training and high intensity efforts. RESULTS: Paired t-tests revealed no significant difference between January and April for peak power, power at LT, O2peak, hGH at LT and hGH at peak exercise. Only the performance measure, distance covered during the sixth 4-minute effort, demonstrated a significant difference (p<0.05), increasing from 1327.05m ± 23.90 in January to 1346.47m ± 30.71 in April (mean ± SD). CONCLUSION: No change was seen in the EIGR. Assuming hGH is involved in the adaptive response then, since there was no change to selected physiological parameters, this result is not surprising. An improvement was seen however, as determined by the distance covered during maximal exercise and arguably this could be attributed to improvement in technique. This finding is consistent with out of season training for elite athletes where ‘maintenance’ of physiological condition is key whilst technical improvements are sought. However, such information on elite individuals is rarely presented in the research literature.