Decreased rate of leg extensor force development in independently ambulant patients with acute stroke with mild paresis

We aimed to examine the rate of force development (RFD) of knee extensors on both sides in independently ambulant patients with acute stroke with mild paresis compared with that in age-matched healthy adults. A total 31 patients with acute stroke history (patient group: 67 ± 12 years) and 54 age-matched healthy, community-dwelling adults (control group: 67 ± 8 years) were included. Maximum voluntary contraction (MVC) and RFD were assessed <1 month post-stroke during isometric knee extension (sitting position; 90° knee flexion) using a hand-held dynamometer. RFD was measured as the average slope of the torque–time curve over time intervals of 0–50 ms and 0–200 ms from contraction onset. In the patient group, MVC and RFD for 0–50 ms were significantly lower on the affected side than on the unaffected side (p < 0.01). RFD was significantly decreased in the patient group, to 32%–38% and 62%–71% of that in the control group, over 0–50 ms and 0–200 ms, respectively, regardless of the affected side (p < 0.01). No significant differences in MVC between patient and control groups were observed for either side. RFD of the knee extensors significantly decreased without MVC reduction in patients with acute stroke history compared with that in age-matched healthy adults in both the affected and unaffected sides. These results suggest that decrease in RFD was initiated from the acute phase of stroke, even in patients with stroke who had good motor function.