The aim of this study is to evaluate a novel composite measure of active range of motion (X_A) and determine whether this measure correlates with active function.

Post hoc analysis of two randomized, placebo-controlled, double-blind studies with open-label extensions exploring changes in active function with abobotulinumtoxinA.

Tertiary rehabilitation centers in Australia, Europe, and the United States.

Adults with upper (n = 254) or lower (n = 345) limb spastic paresis following stroke or brain trauma.

AbobotulinumtoxinA (⩽5 treatment cycles) in the upper or lower limb.

X_A was used to calculate a novel composite measure (CX_A), defined as the sum of X_A against elbow, wrist, and extrinsic finger flexors (upper limb) or soleus and gastrocnemius muscles (lower limb). Active function was assessed by the Modified Frenchay Scale and 10-m comfortable barefoot walking speed in the upper limb and lower limb, respectively. Correlations between CX_A and active function at Weeks 4 and 12 of open-label cycles were explored.

CX_A and active function were moderately correlated in the upper limb (P < 0.0001–0.0004, r = 0.476–0.636) and weakly correlated in the lower limb (P < 0.0001–0.0284, r = 0.186–0.285) at Weeks 4 and 12 of each open-label cycle. Changes in CX_A and active function were weakly correlated only in the upper limb (Cycle 2 Week 12, P = 0.0160, r = 0.213; Cycle 3 Week 4, P = 0.0031, r = 0.296). Across cycles, CX_A improvements peaked at Week 4, while functional improvements peaked at Week 12.

CX_A is a valid measure for functional impairments in spastic paresis. CX_A improvements following abobotulinumtoxinA injection correlated with and preceded active functional improvements.