Purpose: This study assessed whether liquid carbohydrate-protein (C + P) supplements, ingested early during recovery, enhance muscle glycogen resynthesis versus isoenergetic liquid carbohydrate (CHO) supplements, given early or an isoenergetic solid meal given later during recovery (PLB).
Methods: Two hours after breakfast (7.0 kcal·kg−1; 0.3 g·kg−1 P, 1.2 g·kg−1 C, 0.1 g·kg−1 F), six male cyclists performed a 60-min time trial (AMex). Pre- and postexercise, vastus lateralis glycogen concentrations were determined using nMRS. Immediately, 1 h, and 2 h postexercise, participants ingested C + P (4.8 kcal·kg−1; 0.8 g·kg−1 C, 0.4 g·kg−1 P), CHO (4.8 kcal·kg−1; 1.2 g·kg−1 C), or PLB (no energy). Four hours postexercise, a solid meal was ingested. At that time, C + P and CHO received a meal identical to breakfast, whereas PLB received 21 kcal·kg−1 (1 g·kg−1 P, 3.6 g·kg−1 C, 0.3 g·kg−1 F); energy intake during 6 h of recovery was identical among treatments. After 6 h of recovery, measurement and cycling protocols (PMex) were repeated.
Results: Absolute muscle glycogen utilization was 18% greater (P ≤ 0.05) during AMex (C + P: −42.75 ± 5.24 mmol·L−1; CHO: −37.08 ± 7.59 mmol·L−1; PLB: −53.78 ± 11.59 mmol·L−1; P = 0.302) relative to PMex (C + P: −38.40 ± 4.37 mmol·L−1; CHO: −31.16 ± 3.78 mmol·L−1; PLB: −40.33 ± 1.47 mmol·L−1; P = 0.292), but there were no differences between groups. During 6 h of recovery, muscle glycogen resynthesis was greater in C + P (+ 28.62 ± 2.10 mmol·L−1) versus CHO (+ 22.20 ± 1.19 mmol·L−1, P ≤ 0.05) or PLB (+ 18.50 ± 7.67 mmol·L−1, P ≤ 0.05). Cycling performance was similiar (P = 0.282) among treatments during both AMex (C + P: 37.61 ± 0.63 km; CHO: 37.03 ± 0.60 km; PLB: 37.24 ± 0.34 km) and PMex (C + P: 36.31 ± 0.83 km; CHO: 36.38 ± 0.80 km; PLB: 35.34 ± 0.45 km).
Conclusions: C + P supplements, given early after exercise, enhance glycogen resynthesis relative to CHO and PLB. However, this does not influence performance in this type of exercise bout.
1Exercise Nutrition Research Laboratory, Faculty of Health Sciences, School of Kinesiology, The University of Western Ontario, Ontario, CANADA; and 2Department of Diagnostic Radiology, Yale University School of Medicine, New Haven, CT
Address for correspondence: John M. Berardi, Ph.D., 90 Sumach St #604, Toronto, ON, M5A4R4, Canada; E-mail: firstname.lastname@example.org.
Submitted for publication July 2005.
Accepted for publication November 2005.