Resistance Training Induce Changes in Muscle Fiber Morphology and Muscle Architecture in Elderly After Hip Surgery

Abstract

It is well known that a substantial amount of muscle mass and muscle strength is lost during joint-surgery related immobilization. The contribution of changes in muscle architecture has however, never been studied in elderly postoperative patients. PURPOSE: The aim of the present study was therefore to compare the change in muscle size and muscle architecture induced by unilateral Resistance Training (RT) or Electrical Stimulation (ES) of the quadriceps muscle compared to a Standard Rehabilitation (SR) program after hip-replacement surgery. METHODS: Twenty-eight elderly patients (60–86 yrs) scheduled for unilateral hip replacement were randomized to either 1)RT (3/wk-12 wks), 2)ES (1 h/day-12 wks) or 3) SR (1 h/day-12 wks). Muscle biopsies were obtained from vastus lateralis (VL) of both legs at baseline, 5 and 12 wks post-surgery to analyze for changes in muscle fiber CSA. Muscle fiber pennation angle in the VL muscle was measured by use of ultrasonography. Non-parametric tests were used for statistical analyses (significance level, p<0.05). RESULTS: RT increased type I (3464±205 to 4048±375 μm2, p<0.05), type IIa (2732±293 to 3760±671 μm2, p<0.05) and type IIx (2183±449 to 3334±711 μm2, p<0.05) muscle fiber CSA 12 wks post surgery, whereas there was no increase with ES and SR. Furthermore, muscle fiber pennation angle increased by 20% with RT (7.2±0.50 to 8.6±0.60) while there was a decrease by 13% (p<0.05) after 12 wks of SR. The non-operated side remained unchanged in all three groups. DISCUSSION: The present study is the first to demonstrate that resistance training initiated in the acute (1–2 days) postoperative phase is highly effective in increasing muscle fiber area of both type I (+17%), type IIa (+38%) and type IIx fibers (+52%). In addition, RT also induced marked alterations in muscle architecture by increasing muscle fiber pennation angle (+20%) of the VL muscle compared to electrical stimulation and a standard rehabilitation regime.