title: Protein intake does not increase vastus lateralis muscle protein synthesis during cycling.
abstract: OBJECTIVE
  This study aimed to investigate the effect of protein ingestion on leg protein turnover and vastus lateralis muscle protein synthesis during bicycle exercise and recovery.
  
  
  METHODS
  Eight healthy males participated in two experiments in which they ingested either a carbohydrate solution (CHO) providing 0.49 g·kg(-1)·h(-1), or a carbohydrate and protein solution (CHO + P) providing 0.49 and 0.16 g·kg(-1)·h(-1), during 3 h of bicycle exercise and 3 h of recovery. Leg protein turnover was determined from stable isotope infusion (l-[ring-C6]phenylalanine), femoral-arterial venous blood sampling, and blood flow measurements. Muscle protein synthesis was calculated from the incorporation of l-[ring-C6]phenylalanine into protein.
  
  
  RESULTS
  Consuming protein during exercise increased leg protein synthesis and decreased net leg protein breakdown; however, protein ingestion did not increase protein synthesis within the highly active vastus lateralis muscle (0.029%·h(-1), ± 0.004%·h(-1), and 0.030%·h(-1), ± 0.003%·h(-1), in CHO and CHO + P, respectively; P = 0.88). In contrast, consuming protein, during exercise and recovery, increased postexercise vastus lateralis muscle protein synthesis by 51% ± 22% (0.070%·h(-1), ± 0.003%·h(-1), and 0.105%·h(-1), ± 0.013%·h(-1), in CHO and CHO+P, respectively; P < 0.01). Furthermore, leg protein net balance was negative during recovery with CHO intake, whereas positive leg protein net balance was achieved with CHO+P intake.
  
  
  CONCLUSIONS
  We conclude that consuming protein during prolonged bicycle exercise does not increase protein synthesis within highly active leg muscles. However, protein intake may have stimulated protein synthesis within less active leg muscles and/or other nonmuscle leg tissue. Finally, protein supplementation, during exercise and recovery, enhanced postexercise muscle protein synthesis and resulted in positive leg protein net balance.
authors.affiliation: Metabolic Mass-Spectrometry Facility, Rigshospitalet, Copenhagen, Denmark. carl.hulston@brunel.ac.uk
authors.forename: Carl J
authors.initials: CJ
authors.lastname: Hulston
authors.forename: Emil
authors.initials: E
authors.lastname: Wolsk
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Grøndahl
authors.forename: Christina
authors.initials: C
authors.lastname: Yfanti
authors.forename: Gerrit
authors.initials: G
authors.lastname: VAN Hall
mesh_terms: D000596:Amino Acids / Q000097:blood; D001642:Bicycling; D004040:Dietary Carbohydrates / Q000008:administration & dosage; D004044:Dietary Proteins / Q000008:administration & dosage*; D015444:Exercise; D005080:Exercise Test; D006801:Humans; D007328:Insulin / Q000097:blood; D007866:Leg / Q000502:physiology; D008297:Male; D009124:Muscle Proteins / Q000096:biosynthesis*; D010101:Oxygen Consumption / Q000502:physiology; D010649:Phenylalanine / Q000097:blood / Q000378:metabolism / Q000494:pharmacology; D052097:Quadriceps Muscle / Q000378:metabolism*; D055815:Young Adult
chemical_list: D000596:Amino Acids; D004040:Dietary Carbohydrates; D004044:Dietary Proteins; D007328:Insulin; D009124:Muscle Proteins; D010649:Phenylalanine