RESULTS AND DISCUSSION
This study evaluated the behavior of salivary cortisol levels during a long CrossFit® championship. The initial hypothesis, found in literature review, is that salivary cortisol levels increase after workouts. However, this was not demonstrated in this study. Athletes’ saliva samples were collected in the morning, before the competition (D1A – 15.9 ± 10.3 ng/mL, D2A – 13.2 ± 8.0 ng/mL, and D3A – 13.1 ± 9.9 ng/mL), and immediately after the last workout (D1P – 6.4 ± 6.9 ng/mL, D2P – 9.6 ± 7.9 ng/mL, and D3P – 7.1 ± 6 , 7 ng/ml). A statistically significant difference (Figure 1) was found only in D1P compared to D1A, although data showed a trend of fall in cortisol levels throughout the day, indicating that the circadian rhythm of cortisol seemed to react as expected7.
In general, the literature has emphasized that the behavior of cortisol varies according to the intensity of physical exercise; thus, the higher the intensity, the greater the need to mobilize amino acids of tissues. Concurrently, the transportation of cortisol from the extracellular zone to the liver cell increases, which increases their availability for further conversion to glucose. In addition, the increased peripheral destruction of cortisol, the decreased hepatic metabolism rate and the increased ACTH secretion, mostly derived from the influence of stress-related mechanisms, also contribute to increased cortisol secretion during physical exercises7.
Authors, such as Nunes et al.8, demonstrated increases in cortisol concentrations during endurance, power and hypertrophy exercise protocols. This increase is related to the intensity of the physical effort performed; the high metabolic demand of higher efforts tend to induce higher concentrations of cortisol. The idea that CrossFit® is considered an extreme exercise program9supports this fact. However, this study’s data showed that the physiological condition of cortisol behavior was maintained.
Other authors have stated that increased cortisol levels play an important role in athletes’ performance, ultimately meeting their physical demands during a long-term competition10,11,12. Some authors have corroborated that cortisol increases during recovery, indicating a delay in post-training cortisol secretion in women13,14.
Georgopoulos et al.15 found that female Olympic gymnasts showed higher stress response, and their salivary cortisol showed an inverse relation to fat percentage. However, this study was conducted with adolescent gymnasts, who were thinner than the Average female gymnasts at their age, had delayed skeletal maturation, suffered from amenorrhea, and had a significant reduction in fat mass. This phenotype probably results from multifactorial events; that is why this behavior cannot be applied to this study.
Our findings, however, contradict the research studies presented above. In our study, Figure 1 shows the mean values and confidence intervals for each concentration of salivary cortisol (ng/mL) at each time on evaluation days, in the pre and post phase. All athletes presented a physiological performance contrary to the one expected concerning the cycle of cortisol after a competition based on salivary cortisol. This finding may partially result from the behavior of cortisol secretion/metabolism.
Figure 2 reveals that there was a statistical difference (p>0.05) in the concentration of salivary cortisol (ng/mL) between each group of evaluation days.
Figure 1. Mean values and confidence intervals for each concentration of salivary cortisol (ng/mL) at each time on evaluation days.