Effect of three different dairy protein beverages on muscle protein synthesis after exercise

Consumption of the proprietary milk protein concentrate (pMPC) containing 25.0g of dairy protein, 1.3g of carbohydrate and 0.5g of fat dissolved in 200mL of water. Energy = 458kJ. At baseline all participants will undergo DXA and pqCT scans to estimate body composition on muscle size as well as isometric strength measurements. Participants will consume a standardised meal (60% carbohydrate, 20% protein and 20% fat) the night before the trial and must be in an overnight fasted state when arriving at the CRU by 0800h. A muscle biopsy will be taken after a 30 minute rest, and then followed by a blood sample. The participants will then undergo a primed constant infusion of 13C6 phenylalanine (prime: 2 micromol kg-1; infusion: 0.05 micromol kg-1 min-1) for the rest of the trial duration. Blood samples will be taken again every hour for the next three hours. Immediate after the third blood sample a second muscle biopsy from the contralateral leg will be obtained. The participant will then complete three sets of leg presses and leg extensions using both legs on commercial gym equipment. Each set will be at a load of 80% of 1RM and repetitions will be preformed until the point of momentary muscle fatigue. Two minutes of rest will be taken between each set and exercise. all exercise will be supervised by a trained investigator. The total duration of the exercise will be approximately 20 minutes. Immediately after exercise they will consume one of three protein beverages. Beverage consumption will take place within 5 minutes and will be supervised by an investigator in order to ensure compliance. Several blood samples will be taken from the participant up to 240 min. Further muscle biopsies will be taken at 120 min and 240 min after beverage consumption.