Background and purpose: Stroke survivors experience disproportionate muscle atrophy and other detrimental tissue composition changes on the paretic side. The purpose was to determine whether myostatin levels are higher in paretic vs nonparetic muscle and the effects of resistive training (RT) on paretic and nonparetic mid-thigh muscle composition and myostatin mRNA expression in stroke survivors.
Methods: Fifteen stroke survivors (50-76 years) underwent bilateral multi-slice thigh CT scanning from the knee to the hip, bilateral vastus lateralis skeletal muscle tissue biopsies, a total body scan by dual-energy X-ray absorptiometry, and 1-repetition maximum strength test before and after a 12-week, (3 times/week) RT intervention.
Results: Total body fat mass and fat-free mass did not change. Bilateral leg press and leg extension 1-repetition maximum strength increased 31% to 56% with RT (P<0.001). Paretic and nonparetic muscle area of the mid-thigh increased 13% (P<0.01) and 9% (P<0.05), respectively, after RT. Muscle attenuation of the mid-thigh increased 15% and 8% (both P<0.01) in the paretic and nonparetic thigh, respectively, representing reduced intramuscular fat. Muscle volume increased 14% (P<0.001) in the paretic thigh and 16% (P<0.05) in the nonparetic thigh after RT. Myostatin mRNA expression levels were 40% higher in the paretic than nonparetic muscle (P=0.001) at baseline and decreased 49% in the paretic muscle (P<0.005) and 27% in the nonparetic muscle (P=0.06) after RT.
Conclusions: Progressive RT stimulates significant muscle hypertrophy and intramuscular fat reductions in disabled stroke survivors. The increased myostatin mRNA in the paretic thigh and reduction with RT imply an important regulatory role for myostatin after stroke.