Study aim: General Objective:The effect of caffeine supplementation on corticomuscular coherence at specified RPE scales during cycling to exhaustion in active women. Design: A randomized, double-blind, crossover clinical trial conducted on 15 participants. Settings and conduct: This study will be conducted at the Exercise Physiology Laboratory of Alzahra University. In the familiarization session. An incremental cycling test will be performed to determine the anaerobic threshold using the V-slope method, starting with a 4-minute warm-up at 75 watts (70 rpm), followed by 25-watt increments every 2 minutes until exhaustion (RPE = 10) or inability to maintain cadence above 50 rpm. In the main session, participants will have EEG and EMG electrodes placed (according to SENIAM method), and baseline resting EEG will be recorded. They will then consume caffeine or placebo, and maximum voluntary contraction will be measured. After 60 minutes, resting EEG and heart rate will be recorded. The bicycle will be adjusted for participant comfort. The fatigue protocol involves a 4-minute warm-up at 60% of anaerobic threshold, followed by cycling at a constant workload (anaerobic threshold + 5%) until exhaustion, with RPE reported throughout. Participants/Inclusion and exclusion criteria: Inclusion Criteria:Physically active (150–300 min/week moderate aerobic exercise), healthy, normal BMI, no tobacco/alcohol/CNS-active drugs/sports supplements, moderate caffeine intake (≤70 mg/day), regular menstrual cycles (26–32 days).Exclusion Criteria: Acute illness/injury preventing participation, or unwillingness to cooperate. Intervention groups: Caffeine capsule (6 mg/kg bw) and placebo capsule (wheat bran), identical to caffeine Main outcome variables: Time to exhaustion during cycling; Corticomuscular coherence in the rectus femoris and gastrocnemius and vastus medialis and biceps femoris muscle at specified RPE scales