Effects of macronutrient intake on thigh muscle mass during home-based walking training in middle-aged and older women

We examined whether post-exercise macronutrient supplementation during a 5-month home-based interval walking training (IWT) accelerated exercise-induced increases in skeletal muscle mass and strength in healthy middle-aged and older women. Thirty-five women (41-78 years) were randomly divided into two groups: IWT alone (CNT, n=18) or IWT plus post-exercise macronutrient (7.6g protein, 32.5g carbohydrate, and 4.4g fat) supplementation (NUT, n=17). For IWT, all subjects were instructed to repeat five or more sets of 3-min low-intensity walking at 40% peak aerobic capacity (Vo(2 peak)), followed by a 3-min high-intensity walking above 70% Vo(2 peak) per day for 4 or more days per week. We determined Vo(2 peak), thigh muscle tissue area by computer tomography, and thigh muscle strength in all subjects before and after IWT. We found that an increase in hamstring muscle tissue area was 2.8 +/- 1.2% in NUT vs -1.0 +/- 0.7% in CNT and that in isometric knee flexion force was 16.3 +/- 3.7% in NUT vs 6.5 +/- 3.0% in CNT; both were significantly higher in NUT than in CNT (both, P<0.001). Thus, post-exercise macronutrient supplementation enhanced the increases in thigh muscle mass and strength, although partially, in home-based IWT in middle-aged and older women.