Knee extensor muscles strength indicates global lower-limb strength in individuals who have suffered a stroke: A cross-sectional study

Objectives: This study had three aims: (1) to evaluate the relationships between the paretic knee extensor muscle strength and global lower-limb strength in individuals who had suffered a sub-acute/chronic stroke, (2) to determine whether global lower-limb strength, sex, body mass index, or age could predict knee extensor muscle strength, and 3) to investigate whether the results obtained via a Modified Sphygmomanometer Test (MST) would be similar to those obtained using a hand-held dynamometer.

Methods: This was a cross-sectional study, performed at a research laboratory, at participants' homes, or at outpatient clinics. Forty-two individuals with a sub-acute stroke and 45 individuals with a chronic stroke participated. Maximum isometric strength of the paretic lower-limb muscles (i.e. hip, knee, and ankle flexors/extensors, hip abductors) was measured using the MST and a hand-held dynamometer.

Results: Significant and high correlation coefficients were found between knee extensor muscle strength and global lower-limb strength as measured by the combined strength values of 6 lower limb muscle groups in individuals with sub-acute (0.81≤r≤0.88; p<0.05) and chronic (0.82≤r≤0.85; p<0.05) stroke. Step-wise multiple regression analysis revealed that only global lower-limb strength was retained in the model and accounted for 66-78% and 67-72% (p<0.001) of the variance in knee extensor muscle strength at the sub-acute and chronic phases post-stroke, respectively. The results obtained via the MST were similar to those obtained using the hand-held dynamometer.

Conclusion: Paretic knee extensor muscles strength, assessed using a MST or a hand-held dynamometer, indicates global lower-limb strength in individuals with a sub-acute or chronic stroke.