Purpose: 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-13C6]phenylalanine), femoral-arterial venous blood sampling, and blood flow measurements. Muscle protein synthesis was calculated from the incorporation of l-[ring-13C6]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.
1Metabolic Mass-Spectrometry Facility, Rigshospitalet, Copenhagen, DENMARK; 2Copenhagen Muscle Research Centre, Rigshospitalet, Copenhagen, DENMARK; 3Centre of Inflammation and Metabolism, Rigshospitalet, Copenhagen, DENMARK; and 4Department of Biomedical Sciences, Faculty of Health Sciences, University of Copenhagen, DENMARK
Address for correspondence: Carl John Hulston, Ph.D., Centre for Sports Medicine and Human Performance, Brunel University, Uxbridge, Middlesex, UB8 3PH, United Kingdom; E-mail: firstname.lastname@example.org.
Submitted for publication November 2010.
Accepted for publication February 2011.