Aerobic Exercise Training Increases Skeletal Muscle Protein Turnover in Healthy Adults at Rest
2006
Pikosky, Matthew A. | Gaine, Patricia C. | Martin, William F. | Grabarz, Kimberly C. | Ferrando, Arny A. | Wolfe, Robert R. | Rodriguez, Nancy R.
The effect of a 4-wk aerobic exercise training program (30-45 min, 3-5 d/wk, [>/=]65% maximal heart rate) on mixed skeletal muscle protein fractional synthetic rate (FSR), fractional breakdown rate (FBR), and net protein balance (FSR - FBR) (NET) was examined in 8 healthy, previously unfit men and women [21.0 ± 0.4 y, 163.7 ± 4.4 cm, 75.6 ± 5.7 kg, 33.5 ± 4.1% body fat, VO[subscript 2peak] 38.6 ± 2.3 mL/(kg·min)] fed eucaloric diets providing 0.85 g protein/(kg·d) for the 6-wk study. Measurements were made at baseline after 2 wk of diet intervention only, and after 4 wk of aerobic exercise training and diet intervention. Primed continuous infusions of ring-[²H₅]-phenylalanine (2 [micro]mol/kg; 0.05 [micro]mol/(kg·min) and [¹⁵N]-phenylalanine (2 [micro]mol/kg; 0.05 [micro]mol/(kg·min) were used to assess skeletal muscle protein turnover at rest via the precursor-product method. Endurance training improved cardiovascular fitness, with a significant increase in VO[subscript 2peak] (P < 0.01) and a significant decrease in running time on a standard course (P < 0.01). There were no significant changes in body mass or composition. There was a significant increase in FSR (0.077 ± 0.007 vs. 0.089 ± 0.006%/h, P < 0.05) and decrease in NET (FSR - FBR) (-0.023 ± 0.004 vs. -0.072 ± 0.012%/h, P < 0.05); FBR tended to increase (0.105 ± 0.014 vs. 0.143 ± 0.018%/h; P = 0.06) after training. Findings show that aerobic training for 4 wk increases skeletal muscle protein turnover in previously unfit subjects.
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