Isoenergetic Pre-Exercise Meals Varying in Carbohydrate Similarly Affect Resistance Training Volume Performance Compared to Placebo: A Crossover Trial

Abstract

Carbohydrate is an important fuel during moderate- to high-intensity exercise. We hypothesised that pre-exercise carbohydrate ingestion would improve resistance training (RT) volume performance. In a crossover design, sixteen resistance-trained participants (male = 13 and female = 3) performed 3 sets of back squats, bench press, prone row, and shoulder press to repetition fatigue at 80% of 1-repetition maximum (∼90 min). Two hours prior, in randomised order, participants ingested high carbohydrate (HCHO; 1.2 g/kg body mass), low carbohydrate (LCHO; 0.3 g/kg body mass), or a low-calorie placebo (PLA), taste- and texture-matched liquid breakfasts. Linear mixed models were used to analyse volume performance, subjective appetite ratings, and blood glucose and lactate. There were no significant differences between conditions for repetitions completed per session (p = 0.318) or exercise (p = 0.973). Pre-exercise and postexercise hunger was similar between conditions (p = 0.155). Satiation was greater in HCHO and LCHO versus PLA postbreakfast (p = 0.007 and p = 0.002, respectively) and pre-exercise (p = 0.001 and p = 0.002). Fullness was greater in HCHO and LCHO versus PLA postbreakfast (p = 0.001 and p = 0.001, respectively) and pre-exercise (p < 0.001 and p < 0.001). Blood lactate was greater mid- (p < 0.001) and postexercise (p < 0.0001) and was similar between conditions (p = 0.897). Blood glucose significantly increased 30 min after breakfast in HCHO versus LCHO and PLA (p < 0.001) and was similar between conditions postexercise (p = 1.000). The macronutrient or energy composition of a pre-exercise meal does not enhance upper-body-dominant RT volume.