Protein to Maximize Whole-Body Anabolism in Resistance-trained Females after Exercise

Introduction Current athlete-specific protein recommendations are based almost exclusively on research in males. Purpose Using the minimally-invasive indicator amino acid oxidation (IAAO) technique, we determined the daily protein intake that maximizes whole body protein synthesis and net protein balance after exercise in strength trained females. Methods Eight RT females (23 ± 3.5 y, 67.0 ± 7.7 kg, 163.3 ± 3.7 cm, 24.4 ± 6.9% body fat; mean ± SD) completed a 2-d controlled diet during the luteal phase prior to performing an acute bout of whole body resistance exercise. During recovery, participants consumed eight hourly meals providing a randomized test protein intake (0.2-2.9 g⋅kg-1⋅d-1) as crystalline amino acids modelled after egg protein, with constant phenylalanine (30.5 mg⋅kg-1⋅d-1) and excess tyrosine (40.0 mg⋅kg-1⋅d-1) intakes. Steady state whole body phenylalanine rate of appearance (Ra), oxidation (Ox; the reciprocal of protein synthesis, PS) and net protein balance (NB; PS - Ra) were determined from oral [13C] phenylalanine ingestion. Total protein oxidation was estimated from the urinary urea to creatinine ratio (U/Cr). Results A mixed model bi-phase linear regression revealed a breakpoint (i.e., estimated average requirement; EAR) in Ox (r2 = 0.64) of 1.49 ± 0.44 g⋅kg-1⋅d-1 (mean ± 95% CI) and NB (r2 = 0.65) of 1.53 ± 0.32 g⋅kg-1⋅d-1, indicating a saturation in whole body anabolism. U/Cr increased linearly with protein intake (r2 = 0.56, P

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