Supplementary Table S6. Robustness of principal sEMG contrasts after adjustment for participant-by-attachment mean velocity-defined active-motion duration. Muscle / contrast Primary-analysis estimate Unadjusted estimate (same sample) Duration-adjusted estimate Adjusted 95% CI Change after adjustment PD: RP - CB (marginal) 7.96 7.77 7.49 4.53-10.46 -0.28 (3.6%) BB: WVS - SB, lifting 10.95 12.27 12.29 7.94-16.63 +0.02 (0.2%) BB: WVS - CB, lifting 10.59 11.83 11.84 7.51-16.16 +0.01 (0.1%) BB: WVS - RP, lifting 15.66 16.56 16.61 12.37-20.85 +0.05 (0.3%) MT: lowering - lifting (marginal) 6.15 5.62 5.67 2.19-9.16 +0.06 (1.0%) Duration-adjusted estimates were obtained from the attachment × phase mixed-effects model with participant × attachment mean velocity-defined pull/return active-motion duration entered as the corresponding interval-specific covariate (pull duration for the lifting analytical interval and return duration for the lowering analytical interval). The kinematic durations were not time-registered to individual sEMG repetitions. Unadjusted estimates used the same sEMG observations without the duration covariate. Values are reported in the same outcome units as the primary analysis.