Hormonal and metabolic responses to repeated cycling sprints under different hypoxic conditions

• Published in: Growth hormone & IGF research Vol. 25; no. 3; pp. 121 - 126
• Main Authors: Kon, Michihiro, Nakagaki, Kohei, Ebi, Yoshiko, Nishiyama, Tetsunari, Russell, Aaron P
• Format: Journal Article
• Language: English
• Published: Scotland Elsevier Ltd 01.06.2015
• Subjects: Adult; Advanced Basic Science; Endocrinology & Metabolism; Exercise - physiology; Fatty Acids, Nonesterified - blood; Growth hormone; Hormones - blood; Humans; Hypoxia - physiopathology; Lipolysis; Male; Oxygen - metabolism; Supramaximal exercise; Systemic hypoxia; Young Adult; FFA; norepinephrine; SpO 2; E; arterial oxygen saturation; Supramaximal exercise; free fatty acids; AUC; sprint exercise under moderate normobaric hypoxia (16.4% oxygen); Systemic hypoxia; growth hormone; sprint exercise under normoxia; one-repetition maximum; BMI; NSE; GH; HSE 13.6; HSE 16.4; body mass index; epinephrine; area under the curve; 1RM; Lipolysis; NE; sprint exercise under severe normobaric hypoxia (13.6% oxygen); SpO2; Growth hormone
• ISSN: 1096-6374; 1532-2238
• DOI: 10.1016/j.ghir.2015.03.002

Abstract Objective Sprint exercise and hypoxic stimulus during exercise are potent factors affecting hormonal and metabolic responses. However, the effects of different hypoxic levels on hormonal and metabolic responses during sprint exercise are not known. Here, we examined the effect of different hypoxic conditions on hormonal and metabolic responses during sprint exercise. Design Seven male subjects participated in three experimental trials: 1) sprint exercise under normoxia (NSE); 2) sprint exercise under moderate normobaric hypoxia (16.4% oxygen) (HSE 16.4); and 3) sprint exercise under severe normobaric hypoxia (13.6% oxygen) (HSE 13.6). The sprint exercise consisted of four 30 s all-out cycling bouts with 4-min rest between bouts. Glucose, free fatty acids (FFA), blood lactate, growth hormone (GH), epinephrine (E), norepinephrine (NE), and insulin concentrations in the HSE trials were measured before exposure to hypoxia (pre 1), 15 min after exposure to hypoxia (pre 2), and at 0, 15, 30, 60, 120, and 180 min after the exercise performed in hypoxia. The blood samples in the NSE trial were obtained in normoxia at the same time points as the HSE trials. Results Circulating levels of glucose, FFA, lactate, GH, E, NE, and insulin significantly increased after all three exercise trials (P < 0.05). The area under the curve (AUC) for GH was significantly higher in the HSE 13.6 trial than in the NSE and HSE 16.4 trials (P < 0.05). A maximal increase in FFA concentration was observed at 180 min after exercise and was not different between trials. Conclusion These findings suggest that severe hypoxia may be an important factor for the enhancement of GH response to all-out sprint exercise.