Effects Of 24-h Fasting On Human Growth Hormone And Cytokine Responses After Resistance Exercise

Abstract

PURPOSE: This study was to investigate effects of 24-hour fasting on human growth hormone (hGH) and cytokine responses after resistance exercise METHODS: Ten male students (Age; 24.7 ± 1.2 yr, Height; 174.1 ± 2.0 cm, Body Weight; 70.4 ± 1.5 kg) were randomly received to the control treatment (CON) and 24hrs fasting treatment (24-FT). The CON ingested the typical diet (about 400 kcal) prior to 3 hours and performed the resistance exercise, while 24-FT was fasting for 24 hours. The resistance exercise session consisted of squat exercise with 5 sets (8 RM). Blood samples were drawn immediately before (pre) and after (0) exercise and at 15min, 30 min, 60 min, 120 min, 180 min, and 48hrs after exercise. Plasma hGH, IGF-1, total testosterone, cortisol, free fatty acid (FFA), insulin and glucose levels, CK activity, cytokine (IL-6, IL-10, IL-1 B) were determined. RESULTS: Plasma hGH level in 24-FT was significantly increased at 0, 15, 30, 60 min (0.69±0.18, 2.32±0.71, 1.62±0.45, 1.29±0.43 μg/L, respectively) after exercise compared with the CON (0.31±0.04, 0.90±0.31, 0.41±0.08, 0.42±0.14 μg/L, respectively) (p<0.05), but hGH in 24-FT (0.23±0.05 μg/L) was significantly lower than CON at 180 min(0.72±0.23 μg/L) (p<0.05). IL-6 in the 24-FT (48.3±3.6 pg/ml) was significantly increased at 48h after exercise as compared with the CON (39.7±1.5 pg/ml) (p<0.05). CONCLUSIONS: We observed that the fasting did affect hGH releases for 60 min after exercise compared to typical diet in exercise, but this effect in hGH release was disappeared 3 hours after exercise. In addition, we assumed that IL-6 elevation at 48 h after exercise might be due to muscle injury which was caused by the fasting.