Abstract
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.
Key words
endocrine system - testosterone - triathlon - triiodothyronine - shock microcycle - young athletes - interval training
