Abstract
This study investigated the effects of pre-exercise carbohydrate-protein (CHO-PRO) co-ingestion, compared with carbohydrate alone (CHO) and a non-caloric placebo (PLA), on muscle glycogen resynthesis rates and subsequent high-intensity intermittent running performance in trained female field hockey players. In a double-blind, randomized, crossover design, sixteen trained female players (age: 21.4 ± 2.1 years, VO2peak: 52.6 ± 3.8 mL/kg/min) completed three experimental trials separated by a 7-day washout period during the mid-follicular phase of their menstrual cycle. Participants performed an initial glycogen-depleting shuttle run protocol, consumed a pre-exercise beverage (CHO-PRO: 1.0 g/kg CHO + 0.3 g/kg whey protein isolate; CHO: 1.3 g/kg CHO; PLA: flavored water) 120 minutes prior to a 4-hour recovery period, and then completed a simulated match-play performance test (Loughborough Intermittent Shuttle Test, LIST) to exhaustion. Muscle biopsies of the vastus lateralis were obtained immediately post-depletion and prior to the performance test. Muscle glycogen resynthesis rate was significantly higher in CHO-PRO (38.4 ± 4.2 mmol/kg dw/h) compared to CHO (30.1 ± 3.8 mmol/kg dw/h, p = 0.012) and PLA (11.2 ± 2.1 mmol/kg dw/h, p < 0.001). Total distance covered during the LIST to exhaustion was 18.4% greater in CHO-PRO compared to PLA (p < 0.001) and 7.2% greater compared to CHO (p = 0.038). Pre-exercise co-ingestion of CHO-PRO accelerates short-term muscle glycogen synthesis and enhances high-intensity intermittent running capability in female field hockey athletes compared to isoenergetic carbohydrate ingestion alone.
