Timing of postexercise protein intake is important for muscle hypertrophy with resistance training in elderly humans

1. Age-associated loss of skeletal muscle mass and strength can partly be c ounteracted by resistance training, causing a net synthesis of muscular pro teins, Protein synthesis is influenced synergistically by postexercise amin o acid supplementation, but the importance of the timing of protein intake remains unresolved. 2. The study investigated the importance of immediate (P0) or delayed (P2) intake of an oral protein supplement upon muscle hypertrophy and strength o ver a period of resistance training in elderly males. 3. Thirteen men (age, 74 +/- 1 years; body mass index (BMI), 25 +/- 1 kg m( -2) (means +/- S.E.M.)) completed a 12 week resistance training programme ( 3 times per week) receiving oral protein in liquid form (10 g protein, 7 g carbohydrate, 3 g fat) immediately after (P0) or 2 h after (P2) each traini ng session. Muscle hypertrophy was evaluated by magnetic resonance imaging (MRI) and from muscle biopsies and muscle strength was determined using dyn amic and isokinetic strength measurements. Body composition was determined from dual-energy X-ray absorptiometry (DEXA) and food records were obtained over 4 days. The plasma insulin response to protein supplementation was al so determined. 4. In response to training, the cross-sectional area of in. quadriceps femo ris (54.6 +/- 0.5 to 58.3 +/- 0.5) and mean fibre area (4047 +/- 320 to 501 9 +/- 615 mum(2)) increased in the P0 group, whereas no significant increas e was observed in P2. For P0 both dynamic and isokinetic strength increased , by 46 and 15%, respectively (P < 0.05), whereas P2 only improved in dynam ic strength, by 36% (P<0.05). No differences in glucose or insulin response were 5. We conclude that early intake of an oral protein supplement after resist ance training is important for the development of hypertrophy in skeletal m uscle of elderly men in response to resistance training.