abstract
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Resistance exercise training results in skeletal muscle hypertrophy due to accumulated periods ofprotein accretion, the magnitude ofwhich may be influenced by post-exercise feeding. One study suggests that hypertrophy is maximized by immediate provision ofprotein (26); how the type ofprotein ingested in this period affects protein accretion is not known. PURPOSE: To investigate the effect of consuming different post-exercise beverages -milk (MLK), an isonitrogenous and isoenergetic soy drink (PEC), or an isoenergetic control (CON)-on body mass, fat-bone free mass (FBFM), muscle fibre area, and strength during a 12-week progressive whole body resistance training program, in untrained men. METHODS: 34 men were randomized to postexercise consumption ofMLK (n=12; fat free), PEC (n=11; soy) or CON (n=11; maltodextrin) using single-blinded allocation, with characteristics-22.5 ± 0.6 yr, 25.6 ± 0.7 kg/m2• Participants trained 5 d/wk using a whole body split resistance training program and consumed 500 ml oftheir assigned drink immediately and 1h post-exercise following every training bout. RESULTS: Total body mass increased following training (P<0.01) but there were no differences between groups (MLK = 3.2 ± 0.8 kg, PEC = 2.9± 1.4 kg, CON= 2.0 ± 0.8 kg). Similarly, FBFM also increased post-training (P<0.01), but was not different between groups (MLK = 3.3 ± 0.6 kg, PEC = 2.7 ± 0.6kg, CON= 2.2 ± 0.6 kg). Muscle type II fibre area increased post-training (P<0.05) but was not different between groups (MLK = 1004 ± 249 pm2, PEC = 650 ± 192 pm2, CON= 565 ± 120 pm2). Training resulted in increases in 1RM strength for 13 different exercises (P<0.01) with no difference between groups (range= 29-101%). CONCLUSION: Immediate post-exercise provision ofeither milk (MLK), or an isonitrogenous I isoenergetic soy drink (PEC), as well as an isoenergetic carbohydrate beverage (CON), resulted in similar increases in body mass, FBFM, type II muscle fibre area, and strength. This study demonstrates that intact dietary proteins from milk and soy are effective for promoting skeletal muscle hypertrophy. Moreover, when given equivalent energy immediately postexercise, proteins consumed as part of a normal diet, outside ofthe immediate postexercise period are sufficient for hypertrophic and strength gains. Finally, post-exercise consumption ofprotein is no more effective than carbohydrate for promoting skeletal muscle hypertrophy when adequate protein is consumed within a regular diet.