Muscle Atrophy and Functional Deficits of Knee Extensors and Flexors in People with Chronic Stroke

Background: Further clarification is needed with regard to the degree of atrophy in individual muscle groups and its possible relationship to joint torque deficit poststroke.

Objective: The purpose of this study was to investigate quadriceps and hamstring muscle volume and strength deficits of the knee extensors and flexors in people with chronic hemiparesis compared with a control group.

Design: This was a cross-sectional study.

Methods: Thirteen individuals with hemiparesis due to chronic stroke (hemiparetic group) and 13 individuals who were healthy (control group) participated in this study. Motor function, quadriceps and hamstring muscle volume, and maximal concentric and eccentric contractions of the knee extensors and flexors were assessed.

Results: Only the quadriceps muscle of the paretic limb showed reduced muscle volume (24%) compared with the contralateral (nonparetic) limb. There were no differences in muscle volume between the hemiparetic and control groups. The peak torque of the paretic-limb knee extensors and flexors was reduced in both contraction modes and velocities compared with the nonparetic limb (36%-67%) and with the control group (49%-75%). The nonparetic limb also showed decreased extensor and flexor peak torque compared with the control group (17%-23%). Power showed similar deficits in strength (12%-78%). There were significant correlations between motor function and strength deficits (.54-.67).

Limitations: Magnetic resonance imaging coil length did not allow measurement of the proximal region of the thigh.

Conclusions: There were different responses between quadriceps and hamstring muscle volumes in the paretic limb that had quadriceps muscle atrophy only. However, both paretic and nonparetic limbs showed knee extensor and flexor torque and power reduction.