Experimental protocol
fatigue
The study was based on a randomized counterbalanced cross-over design. All experiments took place at the practical demonstration laboratory (Gymnasium), department of physiotherapy, Bayero University, Kano, Nigeria. The participants visited the laboratory four times. The first visit was used to obtain participants’ demographic data (gender, age, height, and weight) and familiarize them with the study procedures. During this visit, the participants received explanation on the study procedures and subjective measurements (mental fatigue visual analogue scale, motivation scale and National Aeronautics and Space Administration (NASA) task load Index) they were expected to fill during their subsequent visits. However, the specific aims and hypotheses of the study were not disclosed to them. Similarly, since they would be required to carry out the Stroop task for induction of mental fatigue, and the balance task during the study, they were also given a practice trial of both tasks (SMBA based mBESS and 120 trials of the Stroop task) during this visit to ensure task familiarization and to mitigate possible learning effects. Subsequently, the order of the experimental and control conditions for each participant was determined at random during this visit. Similarly, the order of the balance assessment i.e., starting with either single or dual task was also randomized with half of the participants starting with single task before dual task and vice-versa.The remaining three visits were allocated to the experimental (induction of mental fatigue, under two conditions) and one control (watching a documentary) condition. Adequate wash-out period (at least 7 days) was allowed between the three sessions to avoid carry-over effects. Participants attended the laboratory at the same time of the day for all conditions to control for circadian effects. They were also instructed to ensure adequate sleep (at least 7 h) the night before; refrain from consumption of caffeine or alcohol 12 h before; and not to engage in rigorous physical exercise 24 h before each of the testing sessions. Participants were interviewed with a checklist of these instructions before each condition to ensure strict compliance. Each condition involved recording the participants single and dual task balance performance using the SMBA based mBESS pre-intervention. During the dual task assessment, the participants completed the balance task while concurrently counting backward by seven from a random number selected by the assessor between 200 and 300. The participants also completed the cognitive task of counting backward by seven for the same duration as the balance task in a seated position as a single task. This and the dual task balance assessment were video recorded, and the total numbers counted backward (both correct and incorrect) were analysed offline.The balance assessment tool and procedure were explained in detail in the outcome measures section below. After the balance assessment, the participants were seated comfortably and asked to fill the questionnaire on motivation and mental fatigue visual analogue scale before performing the Stroop task or watching the documentary. Immediately after completion of the task (Stroop task or watching documentary), they were asked to fill the mental fatigue visual analogue scale again before repeating the balance assessment as done in the pre-test condition. They were then asked to complete the National Aeronautics and Space Administration Task Load Index (NASA) task load index that asked about the perceived workload of the completed experimental or control conditions (Fig. Experimental protocol