Supplementary Table S3. Original repetition-position distribution and interquartile-range-based outlier-screening diagnostics. Repetition position Observations, n 1 446 2 425 3 4 Repetition position refers to the original position within the five-repetition set. The primary sEMG analysis retained the first two repetitions meeting the predefined technique, cadence, signal-quality, and analytical-window criteria; when an earlier repetition was unusable, the next eligible repetition was used. Only four retained analytical-interval observations were coded as repetition position 3, and none were coded as positions 4 or 5. The sensitivity analysis restricted to positions 1 and 2 therefore closely resembled the primary analysis. Muscle Phase Rows flagged by 1.5 × IQR rule Flagged (%) Latissimus dorsi Lifting 0 0.0 Latissimus dorsi Lowering 5 5.9 Middle trapezius Lifting 2 2.3 Middle trapezius Lowering 1 1.2 Posterior deltoid Lifting 4 4.3 Posterior deltoid Lowering 0 0.0 Biceps brachii Lifting 0 0.0 Biceps brachii Lowering 0 0.0 Triceps brachii Lifting 6 6.5 Triceps brachii Lowering 6 7.1 Interquartile-range-based summaries were generated as diagnostic checks only and were not used as automatic exclusion criteria in the reanalysis.