Development and psychometric evaluation of an integrative Manual Muscle Test for patients with post-stroke hemiplegia

Muscle strength is crucial for predicting functional recovery in stroke patients, yet current assessment methods (manual muscle testing and instrument-based dynamometry) are limited in stroke patients due to interference from abnormal synergistic movements and operational complexity/cost, respectively. No validated tool addresses these constraints while quantifying strength across recovery stages.

To develop an integrative manual muscle test (iMMT) for measuring muscle function in stroke patients with abnormal synergistic movements and evaluate its psychometric properties.

An observational study.

Rehabilitation hospital inpatient.

Stroke patients.

The iMMT was developed through a multi-stage process. Initial development involved creating essential movement test items and a novel grading system. This was followed by a pretest to assess operability and refinement of content validity via expert panel review (10 physiotherapists). Finally, a pilot test with 104 stroke patients was conducted to optimize the scale's structure using factor analysis and evaluate its psychometric properties.

The final 17-item iMMT (six upper limb, four trunk, seven lower limb items) was developed with dual six-point grading systems for active range of motion in a normal pattern (A-score) and strength within the active range (B-score) respectively, integrated into a C-score (C=A+B). It demonstrated satisfactory content validity (above moderate relevance), excellent internal consistency (α=0.949), high test-retest (ICC: 0.852-0.992) and inter-tester reliability (ICC: 0.829-0.992). The minimum detectable change (MDC95) was 9.69. Factor analysis confirmed the pre-specified body-part factor structure (AVE>0.5, CR>0.7) and revealed two categories of test items based on postural perturbation (69% variance explained). The iMMT showed excellent convergent and criterion validities demonstrating moderate-to-very-strong correlations with the Fugl-Meyer Assessment (r=0.954), Berg Balance Scale (r=0.747), 10-Meter Walk Test (r=0.769-0.810), the Timed Up and Go test (r=-0.767), Modified Barthel Index (r=0.627), and isokinetic measures (r=0.589-0.773). No ceiling/floor effects were observed.

The iMMT is the first muscle strength tool specifically designed to mitigate synergistic movement interference, providing reliable and valid assessment across stroke recovery stages.

The iMMT provides precise, accessible muscle assessment in hemiplegic patients. This enables identification of specific neuromuscular deficits, thereby guiding targeted strength training and enhancing rehabilitation outcome prediction in clinical practice.