## 4 Discussion
### Future Perspectives  
To date, the primary challenge in using VOT-NIRS is the variety of protocols, instruments, and variables employed to measure muscle metabolism. As in other studies, we acknowledge that desaturation reflects the rate of muscle oxygen consumption, indicating oxygen supply capacity, while resaturation refers to microvascular function, showing the ability to return to an aerobic state [53, 64]. Along with MRT, these measures can indicate oxidative capacity, similar to phosphocreatine (PCr) restoration [65]. Trained individuals are more efficient in switching between oxidative and anaerobic metabolism in response to ischemia and reperfusion (desaturation and resaturation) [64].  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Reliability between Different Days**} & \multicolumn{3}{c}{**Reliability between Fatigue and Non-Fatigue**} \\  & \multicolumn{3}{c}{**(Non-Fatigue)**} & \multicolumn{3}{c}{**Measurements**} \\ \hline
**Variables** & **TE** & **ICC** & **CV\%** & **MDC** & **TE** & **ICC** & **CV\%** & **MDC** \\ \hline Desaturation & 7.3 (5.4 to 11.3) & 0.49 & 5.97 & 7.4 & 8.5 (6.3 to 13.2) & 0.04 & 1.96 & 8.6 \\ Resaturation & 7.4 (5.5 to 11.4) & 0.63 & 14.4 & 7.5 & 9.4 (6.6 to 15.9) & 0.18 & 2.63 & 11.1 \\ Hyperemia & 3.6 (2.6 to 6.1) & 0.57 & 40.5 & 4.3 & 3.3 (2.3 to 5.6) & 0.49 & 11.41 & 3.9 \\ Tau & 11.6 (8.2 to 19.7) & 0.32 & 94.7 & 13.7 & 12.0 (8.5 to 20.4) & 0.03 & 13.67 & 14.2 \\ MRT & 8.2 (5.8 to 13.9) & 0.50 & 9.50 & 9.7 & 12.2 (8.7 to 20.8) & 0.45 & 2.80 & 14.5 \\ \hline Interval R-R & 51.53 (36.5 to 87.5) & 0.94 & 2.95 & 60.9 & 141.7 (100.4 to 240.6) & 0.44 & 0.97 & 167.1 \\ RSMMD & 38.0 (27.0 to 64.6) & 0.98 & 1.76 min & 45.0 & 164.2 (116.3 to 278.7) & 0.21 & 1.96 & 194.0 \\ SDNN & 224.6 (159.1 to 381.3) & 0.43 & 1.58 & 265.4 & 113.3 (80.3 to 192.4) & 0.26 & 2.28 & 133.9 \\ PNS index & 1.5 (1.1 to 2.5) & 0.98 & 15.27 & 1.8 & 5.7 (4.0 to 9.7) & 0.25 & 9.31 & 6.7 \\ SNS index & 0.4 (0.3 to 0.7) & 0.97 & 24.97 & 0.5 & 0.7 (0.5 to 1.1) & 0.61 & 9.63 & 0.8 \\ Mean HR & 3.1 (2.2 to 5.3) & 0.91 & 8.72 & 3.7 & 7.2 (5.1 to 12.3) & 0.59 & 3.76 & 8.5 \\ \hline \hline \end{tabular} Note. ICC interpretation= Value below 0.5: poor reliability; values between 0.5 and 0.75: moderate reliability; values between 0.75 and 0.9: good reliability; values above 0.9 indicate excellent reliability. CVs of \(\leq\)10% and \(\leq\)5% were considered to represent good and excellent reliability, respectively. Variables description: Tau = Constant time, MRT = Mean Response Time, PNS = Parasympathetic nervous system, SNS = sympathetic nervous system, SDNN = the standard deviation of the R-R intervals, and RMSSD = Root mean square successive differences of R-R intervals.  
\end{table}
Table 3: Description of the reliability between the days and conditions of fatigue obtained from resting muscle oxygen consumption and HRV data.  
Similar to [PERSON] et al. [53], we support the hypothesis that resting arterial occlusion is easy to apply and time-efficient, practical for those who cannot tolerate multiple occlusions or perform exercise. For athletes, it is essential to have diagnostic tests that do not require physical exertion and do not interfere with daily training. HRV is known to be sensitive to acute fatigue changes the following day, but the use of SmO\({}_{2}\) as a fatigue marker is still unclear. Longer follow-up protocols should be established to enhance the reliability of the VOT-NIRS test. For example, changes could be observed every hour, and the test should be repeated on different days and under various environmental conditions to establish normative values. Therefore, researchers must continue to refine their studies to reach a consensus that eliminates controversies surrounding the data and improves practical communication. This research proposes using these variables in future fatigue studies.