## 1 Introduction
Key frequency bands studied in exercise research include alpha (8-13 Hz) and beta (13-30 Hz) waves, which are associated with relaxation, cognitive processing, and motor control [25; 27]. Studies indicate that both alpha and beta wave activity increase with exercise intensity, reflecting enhanced neural synchronization and motor planning [24; 28]. However, conflicting evidence exists regarding the patterns of cortical activity during IET, with some studies reporting linear increases, while others observe plateaus or declines in neural activity as fatigue sets in [29; 30]. To our knowledge, only one study, by [PERSON] et al. (2019), has directly compared EEG responses between IET and SPV tests, using RPE as both a dependent and an independent variable [31]. [PERSON] found significant differences between the two protocols, with the SPV test showing continuous increases in alpha and beta activity, while the IET exhibited a peak followed by a decline, suggesting an earlier onset of fatigue. [PERSON] et al. (2019) also employed RPE as an independent variable and used EEG to assess brain activity during the SPV test [28]. Their study, which investigated EEG responses in younger and middle-aged adults, found that alpha and beta wave activity increased with exercise intensity regardless of age, highlighting the effectiveness of RPE in regulating exercise intensity. However, unlike [PERSON]'s study, [PERSON] did not compare different exercise protocols but rather examined EEG variations within a single self-paced protocol across different age groups. Both studies imposed RPE levels (11, 13, 15, 17, and 20 on [PERSON]'s scale) rather than basing subsequent test steps on the RPE given by subjects at the end of each step [28,31]. Imposing a standard RPE on each subject does not account for individual variations in response. For instance, at an RPE of 15, subjects may be at different percentages of their ventilatory threshold or VO2 max. Our study aims to fill this gap by defining the steps of the second test based on the RPE indicated by subjects at the end of each step of the first test. The primary objectives of this study are (1) to investigate neural responses to self-paced and externally controlled incremental exercise using EEG and (2) to assess whether individuals can effectively regulate their effort based solely on perceived exertion, as indicated by the RPE scale. We hypothesize that alpha and beta power spectral density (PSD) will increase with exercise intensity in both the IET and SPV tests, but this increase will be more pronounced in the incremental exercise test due to higher levels of perceived exertion and physiological strain. Additionally, we expect that a decline in the EEG/VO2 ratio will be observed as exercise intensity increases, particularly in the IET, suggesting that neural activity decreases relative to physiological demand, and potentially serving as a marker of central fatigue. Furthermore, we hypothesize that subjects will demonstrate a capacity to control their exercise intensity accurately using the RPE scale, reflected by similar cardiovascular parameters (VO2, respiratory rate (Rf), HR, power output) between the IET and SPV tests.