Purpose: The aim of this study was to determine whether adding protein to a CHO beverage would improve late-exercise cycle time-trial performance over CHO alone. Furthermore, we examined the effects of coingesting protein with CHO during exercise on postexercise markers of sarcolemmal disruption and the recovery of muscle function.
Methods: In a double-blind, crossover design, 12 trained male cyclists performed 120 min of steady-state (SS) cycling at approximately 55% V˙O2max followed by a time trial lasting approximately 1 h. At 15-min intervals during SS exercise, participants consumed either a CHO or a CHO + protein (CHO + Pro) beverage (providing 65 g·h−1 CHO or 65 g·h−1 CHO plus 19 g·h−1 protein). Twenty-four hours after the onset of the SS cycle, participants completed a maximum isometric strength test. At rest and 24 h postexercise, a visual analog scale was used to determine lower-limb muscle soreness, and blood samples were obtained for plasma creatine kinase concentration. Dietary control was implemented 24 h before and during the time course of each trial.
Results: Average power output sustained during time trial was similar for CHO and CHO + Pro, with no effect of treatment on the time to complete the time trial (60:13 ± 1:33 and 60:51 ± 2:40 (min:s) for CHO and CHO + Pro, respectively). Postexercise isometric strength significantly declined for CHO (15% ± 3%) and CHO + Pro (11% ± 3%) compared with baseline (486 ± 28 N). Plasma creatine kinase concentrations, and visual analog scale soreness significantly increased at 24 h postexercise, with no difference between treatments.
Conclusions: The present findings suggest that CHO + Pro coingestion during exercise does not improve late-exercise time-trial performance, ameliorate markers of sarcolemmal disruption, or enhance the recovery of muscle function at 24 h postexercise over CHO alone.
School of Sport and Exercise Sciences, University of Birmingham, Birmingham, UNITED KINGDOM
Address for correspondence: Asker E. Jeukendrup, Ph.D., School of Sport & Exercise Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, United Kingdom; E-mail: firstname.lastname@example.org.
Submitted for publication July 2009.
Accepted for publication October 2009.