Improving interlimb coordination and paretic limb use after stroke using a novel robotic split-crank pedaling device: a cross-sectional study.

backgroundMany stroke survivors cannot walk effectively, even after rehabilitation. Causes include impaired muscle activation, poor interlimb coordination, and limited restorative interventions. To address this, we developed CUped (pronounced “cupid”), a motorized split-crank pedaling device designed to compel use of the paretic limb and retrain interlimb coordination. We examined its within-session effects, comparing three proportional control schemes—assist (A), resist (R), and assist plus resist (A + R)—to identify which best promotes recovery-related movement.

methodsNineteen individuals with stroke and eleven controls pedaled in 5-min bouts, one per control scheme. Each bout included pre-test, exposure, and post-test periods. Participants were instructed to maintain a 180º interlimb phase relationship. Interlimb coordination and paretic limb use were quantified as the mean and standard deviation of phasing error (µE, σE) and net mechanical work (Wₙₑₜ), respectively. ANOVA was used to assess the effects of group, time, and control scheme; regression examined relationships between variables and conditions. Between-limb differences in pedaling velocity (Vdif) were also calculated and served as interpretive measures.

resultsIn stroke, all control schemes reduced µE, with the largest reduction observed under A + R (p ≤ 0.019; ES: A − 15º, R − 11º, A + R − 21º). Only A + R reduced σE (p = 0.039; ES: −10º). Effects diminished with sustained exposure to control schemes (p < 0.001) and exceeded pre-test when they were terminated (p ≤ 0.027; np2 µE = 0.24, np2 σE = 0.49 ). This “rebound” was associated with an increase in Vdif from pre- to post-test (p < 0.001. np2≥0.53). There was an inverse relationship between baseline phasing error and changes in µE and σE during exposure, where greater baseline error was associated with larger improvements (p < 0.001, R² µE = 0.74, R² σE = 0.69). The R scheme increased Wₙₑₜ, whereas A and A + R reduced it (p ≤ 0.026; ES: A − 8.8 J, R 2.9 J, A + R − 5.8 J). These changes were inversely related to changes in µE (p = 0.002, R²: 0.69). Responses to CUped were similar in controls.

conclusionCUped improved interlimb phasing and paretic limb use, though effects were not enduring, and gains in one reduced the other, with the A + R scheme performing the best overall. Results support CUped’s potential to enhance recovery-related movement and provide insight into motor adaptation post-stroke.