Background: Despite extensive study of the impact of stroke on muscle and functional performance, questions remain regarding the extent to which changes are due to the neurological injury vs. age-related loss of morphology and force production.
Objectives: To synthesize available evidence describing post-stroke changes in lower extremity muscle size and strength compared to healthy adults.
Methods: Scientific literature was searched up to April 2016 to identify studies that included lower extremity muscle size and strength measures in individuals with chronic stroke. Lower extremity muscle size and strength data from healthy controls were sought for comparison. Relative differences were calculated between paretic, nonparetic, and control limbs.
Results: Fifteen studies with 375 participants (61% male; age = 62 ± 5 years; time since stroke = 60 ± 42 months) were included. The paretic limb exhibited deficits of ~13% in thigh muscle size, ~5% in lower leg muscle size, and ~8% in lean leg mass compared to the nonparetic limb. Paretic plantarflexor and knee extensor strength were 52 and 36% lower, respectively, compared to the nonparetic limb. When compared to age-matched control data, both paretic and nonparetic limbs showed deficits in muscle size and strength.
Conclusions: Age-related differences support the impact of stroke-related sarcopenia as a contributor to hemiparetic muscle dysfunction. Understanding these muscular changes is necessary for designing appropriate exercise interventions aimed at restoring muscle function.
Keywords: Stroke; muscle; muscle mass; rehabilitation; sarcopenia; strength; systematic review.