4. Discussion
hypoxia, fatigue
HYPOXIC, HYPOXIA
A high T blood concentration and a favorable T/C ratio are considered important factors influencing the effectiveness of altitude training [The results of our study showed that a 2-week DAA supplemental protocol (6 g per day) did not cause significant beneficial changes in blood testosterone (T, fT) concentration during LH–TL and did not affect the effectiveness of hypoxic exposure in terms of hematological changes in relation to the control group. We showed that in both groups, after the first night spent in hypoxic conditions (after 4 days of supplementation), there was an approx. 20% increase in T concentration in the blood. No significant changes in fT, LH, or C were noted. Changes in the T/C ratio were also observed. Initially, after 12 h of exposure to hypoxia (S2), there was a significant increase in T/C in the DAA group compared to the baseline studies. Notably, the changes in the C group had the same trend, but they were not statistically significant. The increase in the T/C ratio in the DAA group was temporary, and on the following days of the LH–TL protocol (S3 and S4), the T/C values no longer differed significantly from the baseline. In our opinion, the decrease in T/C values during S3 and S4 compared to the S2 measurement was due to the increasing fatigue of the subjects, as evidenced by significant changes in CK activity, as well as an increase in C concentration in the blood.The observed increase in T concentration in the blood during S2 was the effect of 12 h of hypoxic exposure of the subjects, not the effect of the introduced DAA supplementation. Recently, Oyedokun et al. [Our study results, indicating that DAA supplementation does not affect T or fT concentrations, are consistent with previous studies involving male athletes using various DAA doses (1.78 to 6 g per day) over different dosing periods (from 2 to 12 weeks) [As mentioned above, the ineffectiveness of DAA was previously explained by the autoregulatory control of the HPG axis, which may limit endogenous T production when it approaches or exceeds a certain individual threshold. The results of our study suggest that the autoregulatory control of the HPG axis depends on the strength of the stimulus. Our study found that after exposure to normobaric hypoxia, there was a significant increase in blood T concentration in the studied groups. The lack of change in T concentration after DAA supplementation, on the other hand, suggests that the stress caused by hypoxia seems to be a much stronger stimulus in this regard than the effect of DAA.The only potentially beneficial change observed in our study resulting from DAA supplementation appears to be a significantly higher T concentration (by 15% vs. baseline) after 6 nights of the LH–TL protocol (after 9 days of supplementation), despite the accumulation of training loads. In the control group, the T concentration at this time tended to return to baseline values. Additionally, in the control group, on the 5th and 10th days of the experiment, the level of fT in the blood reached values lower than the baseline. In the DAA group, on the other hand, despite increasing fatigue over the consecutive days of training, the fT did not change. However, further analysis of the area under the curve (AUC) for T and fT concentrations in the blood during the entire intervention period did not show significant differences between the DAA and control groups. These findings allow us to conclude that the applied DAA supplementation did not cause significant beneficial changes in blood testosterone concentration during the given LH–TL protocol. In our opinion, the observed changes in the rate of return of T and fT concentrations to baseline values during training are most likely the result of the different reactivity of the subjects to hypoxic conditions and the imposed training loads rather than the effect of DAA.As regards hematological changes, we observed a small but significant (