## 4 Discussion
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Evaluation Moment** & **Pre Event** & \multicolumn{2}{c}{**Day 1**} & \multicolumn{2}{c}{**Day 2**} & \multicolumn{2}{c}{**Day 3**} & \multicolumn{2}{c}{**Day 4**} \\ \hline Participant & 1 & 2 & 1 & 2 & 1 & 2 & 1 & 2 & 1 & 2 \\ \hline Mean HR (bpm) & 65 & 64 & 95 & 92 & 96 & 95 & 94 & 91 & 97 & 92 \\ \hline RMSSD (ms) & 68 & 66 & 18 & 17 & 17 & 18 & 14 & 16 & 15 & 17.5 \\ \hline pNN50 (ms) & 29 & 27 & 2 & 2 & 1.8 & 1.7 & 1.6 & 1.9 & 1.5 & 1.8 \\ \hline Kcal consumed & & 7311.1 & 7215.3 & 7343.8 & 7311.1 & 7278.4 & 7187.6 & 7376.5 & 7215.3 \\ \hline \hline \end{tabular} (RMSSD); Square root of the mean of the sum of the squared differences between adjacent normal R-R intervals; (PNN50); percentage of differences between normal adjacent R-R intervals greater than 50 ms. (Kcal); Kilocalories.  
\end{table} 
Table 3: Heart rate variability and Kcal consumed results pre and during the event. Participant experimental 1 in a fasting situation; participant control 2 with intake. day testing period. Effective stress management is associated with higher performance in ultraendurance tests [14]. In fact, it has been observed that this type of test elicits a moderate level of perceived psychological stress in the case of an athlete with spinal cord injury [23]. Moreover, the literature indicates that prolonged effort in highly demanding situations can deplete psychological resources and hinder their replenishment [24]. However, in the present study, this does not explain the differences found between the calorie-restricted participant and the control. In fact, the performance of highly trained athletes in a fasting state with respect to glucose metabolism appears contradictory. Differences in the duration of fasting or training, the intensity, and characteristics of the participants, necessitate further investigation in this regard [25]. Therefore, it is possible that the hours of fasting prior to the test, the duration of fasting during the event, the type of training performed, or the psychological characteristics of the participant may have contributed to the perception of the event as more stressful for the fasting participant compared to the control participant. In relation to pain perception, the post-test results were higher in the participant who underwent the event in a fasting state compared to the control subject. We know that higher pain tolerance is associated with better performance in ultraendurance tests [14], and it appears that the amount of training hours has an impact on pain tolerance [26]. However, in our study, the total weekly training volume was very similar in both participants. Regarding fasting, research is promising regarding the use of intermittent fasting and its benefits for chronic pain [27], weight loss, control of chronic diseases, and longevity. However, when it comes to the consequences of fasting in athletes, caution is warranted [28]. Hunger has been associated with increased pain in a case study of a non-finisher ultraendurance athlete, demonstrating how hunger enhances a cascade of negative sensations that can negatively influence athlete performance [29]. Therefore, undertaking ultraendurance tests in a fasting state may be linked to an increase in pain perception. However, more research is needed, involving a larger number of fasting ultraendurance athletes, to further investigate this relationship. In line with this, our research found differences in both the quantity and perceived quality of sleep, with lower sleep quality reported by the fasting participant. Evidence shows that sleep loss is associated with decreased performance in multi-day ultraendurance tests [30]. Furthermore, sleep deficiency is linked to a depletion of muscle glycogen stores, impairing muscle recovery and increasing the prevalence of injuries [31]. Therefore, reduced sleep efficiency could be a key factor contributing to increased pain perception and decreased performance in the fasting participant.