## 4 Discussion
Regarding accuracy and correct responses, the 2 min Stroop test was insufficient to promote significant changes. These results differ from those of [PERSON] et al. [19], whose systematic review concluded that mental fatigue protocols led to significant decreases in passing accuracy, as well as in the speed and precision of passes. It also deviates from the results found in the study by [PERSON] et al. [12], where significant decreases were observed in pass accuracy and speed. In line with previous studies, [PERSON] et al. [20] reported a significant increase in failed passes and lost balls by players after undergoing the mental fatigue protocol. These substantial differences may be attributed to the Stroop test duration, which lasted for 30 min [12; 13; 17; 20], while our protocol administered the Stroop test for two minutes. In this regard, when comparing the first- and second-minute results, differences were not observed in accuracy, errors, or total words. Moreover, looking for the minimum dose to induce mental fatigue, our results showed that two minutes of the incongruent Stroop task was insufficient to cause mental fatigue, affecting the accuracy of technical execution and successful decision-making. Although traditionally, longer cognitive tasks have been associated with greater mental fatigue, emerging literature suggests that shorter tasks can also induce notable ego depletion [24], impacting subsequent physical performance [28]. In this regard, short-term mental fatigue protocols based on 10 min of the Stroop test were enough to induce this fatigue state [18; 25]. Nevertheless, there are others studies that did not induce mental fatigue using 10 min of dual-tasking [32]. In relation to this, previous studies in the field of tennis have demonstrated that 12 bouts of 30 s (6 min) of the Stroop test [26; 27] combined with physical exercise may induce mental fatigue. In the same line, a previous study with chess players demonstrated that heart rate variability can be decreased after 5 min of problem solving task [29]. Interestingly, heart rate variability can be considered an indicator of fatigue due to its relationship with autonomic nervous system regulation [44]. Variations in HRV reflect changes in the balance between sympathetic and parasympathetic activity, which often accompany physical and mental fatigue [45]. Therefore, future studies should design protocols that not only measure end results but also incorporate continuous monitoring to identify the precise onset of mental fatigue during tasks. Integrating heart rate variability (HRV) and electroencephalographic (EEG) evaluations would be beneficial; HRV can provide insight into autonomic fatigue responses, while EEG, specifically monitoring theta wave activity, could serve as a robust neuronal biomarker of mental fatigue [46]. Although this approach may be complex due to equipment costs and setting constraints, it could offer valuable insights for team sports training and performance optimization. In addition, future studies should explore the role of supplementation, such as caffeine, in the mental fatigue [47]. The fatigue protocol used in this study was the Stroop test, which involves interference ability (participants must indicate the color of the ink with which a word is written, not matching its meaning) [16]. This task can be conducted using paper-based [12] or electronic devices such as computer, tablet, or smartphone [12; 13; 17]. In our study, we opted for an electronic device, such as a tablet, due to its ease of use and speed when processing data. Existing literature suggests a fatigue-inducing time ranging from 10 min [18] to 30 min [12; 13; 17]. We proposed a more ecological approach by conducting 2 min of cognitive task without breaks. This brevity allows for the administration of shorter tasks in real-world contexts, addressing potential resistance from coaching staff concerning time limitations during training sessions.