The Effect of Whey Protein Supplementation on the Recovery of Contractile Function following Resistance Training: 3369 Board # 238 June 2 9 30 AM - 11 00 AM

PURPOSE: This study investigated the effect of supplemental whey protein (WP) on acute measures of muscle protein fractional synthetic rate (FSR) and the recovery of skeletal muscle contractile function during repeated bouts of resistance training (RT). METHODS: Sixteen resistance-trained men (80 [13] kg body mass; 23 [4] y; 2.6 [1.2] y RT experience; mean [SD]) completed the 7-day dietary supplement intervention study. Subjects were randomly assigned to consume each morning in a double-blind manner either a WP supplement (WP; 0.33 g/kg; n = 8) or an isocaloric, isonitrogenous, non-essential amino acid control (CON; 0.33 g/kg n = 8) with a timed and standardised diet (35 kcal/kg/day; 2 g/kg/day protein). Peak isometric squat force (ISQ) and countermovement jump displacement (CMJ) were used to assess baseline contractile function. Subjects then completed three RT bouts (0.7 1RM back squat; 10 repetitions per set; 0.25 duty cycle; point of exhaustion = 8 [2] sets), every other day. Other activities of daily living did not exceed 3 metabolic equivalents. Repeat measurement of ISQ, CMJ, muscle pain and serum creatine kinase (CK) activity (an index of muscle damage) was taken pre-RT, +24h and +48h post-RT, each bout. Muscle protein FSR was measured between muscle biopsies taken from the vastus lateralis pre- and 5 h post- the first RT intervention using the D(2)O stable isotope tracer technique. The observed changes are reported as the mean [low, high] 90% CI, p-value (P). RESULTS: A 1.0 [0.7, 1.3] fold increase (P < 0.008) in CK and muscle pain (20 [10, 30] %; P = 0.011) was observed +24h the first RT bout only, confirming an absence of overt muscle damage. An acute loss of ISQ was observed following all RT bouts +24h (-19 [-21, -17] %; P < 0.001) and +48h for ISQ (-19 [-21, -17] %; P < 0.001), and +24h for the CMJ (-7 [-9, -5] %; P < 0.05). Whilst acute FSR was increased for WP over and above the CON (+ 0.275 [0.148, 0.403] %/day; P = 0.07), no discernible difference between WP and CON was observed for any measure of contractile function, pain, or CK (P > 0.493). CONCLUSIONS: We conclude that, whilst peri-RT supplementation with WP augments muscle protein FSR, further inference of this pro-anabolic effect should not extend to acute (0 to 48 h) recovery of peri-RT muscle contractile function.