Postexercise muscle glycogen recovery enhanced with a carbohydrate-protein supplement

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 (AM(ex)). 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 (PM..) were repeated. Results: Absolute muscle glycogen utilization was 18% greater (P <= 0.05) during AM(ex) (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 AM(ex) (C + P: 37.61 +/- 0.63 km; CHO: 37.03 +/- 0.60 km; PLB: 37.24 +/- 19.34 km) and PM,, (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.