Acute hormonal responses before and after 2 weeks of HIT in well trained junior triathletes

• Published in: International journal of sports medicine Vol. 35; no. 4; p. 316
• Main Authors: Zinner, C, Wahl, P, Achtzehn, S, Reed, J L, Mester, J
• Format: Journal Article
• Language: English
• Published: Germany 01.04.2014
• Subjects: Adaptation, Physiological; Adolescent; Athletic Performance - physiology; Bicycling - physiology; Hormones - blood; Human Growth Hormone - blood; Humans; Hydrocortisone - blood; Male; Oxygen Consumption; Physical Education and Training - methods; Physical Endurance - physiology; Running - physiology; Swimming - physiology; Testosterone - blood; Triiodothyronine - blood
• ISSN: 1439-3964
• DOI: 10.1055/s-0033-1353141

The aim was to compare the acute hormonal response to a single HIT session at the beginning and end of a HIT shock microcycle. 13 male junior triathletes (15.8±1.8 yrs.) performed 16 HIT sessions within a 2 week period. Venous blood samples were collected before and after the first and last HIT session. Significant increases in cortisol (first session +89.7%; last session +70.3%) and hGH (first session +435.1%; last session +314.6%) concentrations were observed after both training sessions (P<0.05). The acute responses of cortisol, hGH, T3, and fT3 were not different between the first and last HIT sessions (P=1.00). Although no acute changes in testosterone were detected after the training sessions, testosterone concentrations were significantly higher at all time points (62.6-80.1%) during the last compared to first training session (P≤0.001). Findings from the present study reveal that 16 sessions of HIT led to significant increases in baseline concentrations of serum testosterone. This might indicate a heightened anabolic state even in junior triathletes. Based on the hormonal data, we conclude that at the end of this 2 week microcycle no familiarization effect was evident and that the training stimulus produced by HIT was still great enough to "stress" the athletes and induce positive training adaptations.