Mindfulness, Mental Fatigue, Inhibitory Control and Endurance Performance in Athletes

Inhibitory control will be evaluated by a Flanker task in terms of reaction time in this study, and the types of trials are the congruent (i.e., > > > > >) and incongruent (i.e., < < > < <). In the Flanker task, participants were presented with five arrows and instructed to respond as quickly and accurately as possible to the direction where the middle arrow is pointing (i.e., left or right).

Inhibitory control will be evaluated by a Flanker task in terms of accuracy in this study, and the types of trials are the congruent (i.e., > > > > >) and incongruent (i.e., < < > < <). In the Flanker task, participants were presented with five arrows and instructed to respond as quickly and accurately as possible to the direction where the middle arrow is pointing (i.e., left or right).

The endurance performance in terms of time to exhaustion (TTE) will be assessed by graded exercise test (GXT) with Bruce protocol on treadmill (h/p/cosmos pulsar 3p, Germany). The initial speed and grade of the GXT will be set at 2.74 km/hr with grade of 10% and increase speed and grade every 3 min until participants are volitionally exhausted.

The maximal oxygen consumption (VO2max) throughout the whole GXT will be recorded by a computerized indirect calorimetry system (SensorMedics Vmax 29C, USA), and until the participants reached volitional exhaustion. The VO2max in the study will be defined as the highest 30-s average value of VO2 measured during GXT.

Neuroelectrical activity during the Flanker task was recorded using electroencephalography (EEG) with continuous data acquisition throughout task performance. Changes in neuroelectrical activity were operationalized as differences in event-related potential (ERP) amplitudes during the Flanker task (e.g., N2 and P3 components). The mean amplitudes of the N2 and P3 were quantified within predefined time windows of 250-350 ms and 350-550 ms, respectively, following stimulus onset.

Before, after Stroop task, and after Flanker task, changes in subjective mental fatigue was measured using a visual analog scale for mental fatigue (VAS-MF). Participants were asked the following questions "What is your mental fatigue level now?", and participants could indicate how mental fatigue on a scale from 0 (i.e., no mental fatigue at all) to 100 (i.e., completely mentally exhausted).

During the intervention, the reaction time in both Stroop tasks was calculated as an index of objective mental fatigue.

During the intervention, the accuracy in both Stroop tasks was calculated as an index of objective mental fatigue.

Mood state was determined by the difference in scores on the Brunel Mood Scale-Chinese (BRUMS-C) between before (i.e., T0) and after (i.e., T1) Stroop task.

The BRUMS-C consists of 23 items rated on a 5-point Likert scale and comprises six subscales: anger, confusion, depression, tension, fatigue, and vigor. Each subscale score is calculated as the mean of its corresponding items, with possible scores ranging from 0 to 4. Higher mean scores indicate greater intensity of the respective mood state.

The level of effort exerted by participants during the Flanker task and GXT was assessed using the VAS for motivation (VAS-M). Immediately after completing each task, participants were also asked to mark a 100mm line to rate their motivation to perform at their best (i.e., "How motivated are you to perform to the best of your ability in the task?") on a scale ranging from 0, indicating "not at all," to 100, indicating "extremely motivated."