Test-Retest Reliability and Minimal Detectable Change of Body Function Impairment and Activity Limitation Outcomes Using a Mechatronic Evaluation Designed for Inpatient Stroke Research

Objective: To determine the test-retest reliability and minimal detectable change (MDC) scores for 7 precision measures examining upper extremity strength, reaching ability, and the expression of flexion synergy after stroke. The measurements relied on a mechatronic evaluation designed for time efficiency facilitating implementation in inpatient translational research. Design: Observational, analytical, cross-sectional study. Setting: University research laboratory. Participants: Twenty-five participants (N=25) >6 months poststroke with persistent upper extremity body function impairment and activity limitation were recruited using convenience sampling. Interventions: Not applicable. Main Outcome Measures: Shoulder abduction and elbow extension strength measured as a unit of torque (Nm); normalized reaching distance with the arm under 3 conditions: supported, against gravity, and against 50% of shoulder abduction strength; flexion synergy takeover; and emergence thresholds. Results: Twelve male and 13 female participants aged 56.4 ± 17.8 years with a mean time poststroke of 5.37 ± 7.55 years completed the study. The intraclass correlation coefficients for the outcome measures were as follows: shoulder abduction strength (0.963), elbow extension strength (0.983), supported reaching (0.982), reaching against gravity (0.968), reaching against 50% abduction strength (0.974), flexion synergy takeover (0.919), and flexion synergy emergence (0.949) thresholds. The MDC, overall mean, and standard deviation were calculated as follows: shoulder abduction strength (5.69 Nm, 24.44±10.67 Nm), elbow extension strength (5.66 Nm, 18.53±15.66 Nm), supported reaching (0.07, 0.91±0.20), reaching against gravity (0.15, 0.73±0.30), reaching against 50% abduction strength (0.13, 0.69±0.29), flexion synergy takeover (0.14, 0.91±0.17), and flexion synergy emergence (0.17, 0.56±0.27) thresholds. Conclusions: The mechatronic evaluation, although streamlined from more labor-intensive laboratory evaluations, demonstrates excellent (>0.90) test-retest reliability and MDC scores for 7 precision measures of upper extremity body function impairment (weakness and synergy) and activity limitation (reaching).