Effects of Rhodiola Rosea Supplementation on Mental Fatigue, Visuo-cognitive Processing, and Strength Performance

The general warm-up mirrored that of the 1RM assessment. Thereafter, the specific warm-up included for each exercise 2 sets of 3 repetitions at 30% and 50% of 1RM, and a final set of 2 repetitions at 70% of 1RM. The training regimen consisted of 8 alternating sets (4 sets each) of bench press and bench pull, with a 2-minute rest period between sets, performed at 70% of the 1RM load established during the preliminary testing session. Sets were terminated when 2 consecutive repetitions were performed at a MV below 0.35 m·s-1 for the bench press and 0.60 m·s-1 for the bench pull. Participants were encouraged to perform all repetitions at maximal intent, and they received real-time MV feedback (GymAware RS; Kinetic Performance Technologies, Canberra, Australia). Strength performance was assessed by recording the number of repetitions completed (Nrep) and the velocity of the fastest repetition (MVfastest) in each set.

The OMNI-Resistance Exercise Scale (OMNI-RES) of perceived exertion was

In line with the method used by Vera et al. [26] for the MOT test, eight identical black balls (each with a diameter of 1.8 cm) were displayed on a white square background (32.5 cm, luminance of 107 cd/m²) subtending a visual angle of 36°. The stimuli were presented on a 27-inch television monitor (LS27C330GAUXEN) positioned 50 cm away from the participant. At the beginning of each trial, three of the balls were randomly illuminated in green for 2 seconds, after which they reverted to their original black colour. Participants were instructed to track the selected balls for a duration of 10 seconds. No specific strategy was suggested for completing the task, and participants were allowed to use natural eye movements, mirroring real-world scenarios [27,28]. None of the participants had prior experience with the MOT task. The balls moved along linear paths at a constant speed, changing direction only when colliding with each other or the walls.

After the 10-second tracking period, all t

A 30-minutes incongruent Stroop task was used to induce mental fatigue, which requires response inhibition and sustained attention [24] and has demonstrated to be a valid intervention for inducing mental fatigue and impairing physical performance [1,25]. In the incongruent Stroop colour word task, participants were shown lists of colour words (e.g., "blue", "red", "yellow", or "green") on the screen, where the ink colour of the letters did not match the word itself (for example, the word "blue" might be displayed in green ink). For each word, participants were instructed to select the ink colour rather than reading the word. After each response, a new word was presented. The control condition consisted of watching an emotionally neutral documentary during 30 minutes in the same screen (LS27C330GAUXEN, 27", Samsung, Seoul, Korea) used for the Stroop task. Participants remained seated in the same room and in the same position for both interventions (50 cm from the screen).