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Introduction: Protein ingestion during recovery from exercise has been reported to augment myofibrillar protein synthesis rates, without increasing muscle connective protein synthesis rates. It has been suggested that collagen protein may be effective in stimulating muscle connective protein synthesis. The present study assessed the capacity of both whey and collagen protein ingestion to stimulate postexercise myofibrillar and muscle connective protein synthesis rates. Methods: In a randomized, double-blind, parallel design, 45 youngmale (n = 30) and female (n = 15) recreational athletes (age, 25 ± 4 yr; bodymass index, 24.1 ± 2.0 kg·m-2) were selected to receive primed continuous intravenous infusions with L-[ring-13C6]-phenylalanine and L-[3,5-²H2]-tyrosine. After a single session of resistance type exercise, subjects were randomly allocated to one of three groups ingesting either 30 g whey protein (WHEY, n = 15), 30 g collagen protein (COLL, n = 15) or a noncaloric placebo (PLA, n = 15). Blood and muscle biopsy samples were collected over a subsequent 5-h recovery period to assess both myofibrillar and muscle connective protein synthesis rates. Results: Protein ingestion increased circulating plasma amino acid concentrations (P < 0.05). The postprandial rise in plasma leucine and essential amino acid concentrations was greater in WHEY compared with COLL, whereas plasma glycine and proline concentrations increased more in COLL compared with WHEY (P < 0.05). Myofibrillar protein synthesis rates averaged 0.041 ± 0.010, 0.036 ± 0.010, and 0.032 ± 0.007%·h-1 in WHEY, COLL and PLA, respectively, with onlyWHEY resulting in higher rates when compared with PLA (P < 0.05). Muscle connective protein synthesis rates averaged 0.072 ± 0.019, 0.068 ± 0.017, and 0.058 ± 0.018%·h-1 in WHEY, COLL, and PLA, respectively, with no significant differences between groups (P= 0.09). Conclusions: Ingestion of whey protein during recovery fromexercise increasesmyofibrillar protein synthesis rates. Neither collagen nor whey protein ingestion further increased muscle connective protein synthesis rates during the early stages of postexercise recovery in both male and female recreational athletes. [ABSTRACT FROM AUTHOR]