Carbohydrate Mouth Rinsing Does Not Alter Central or Peripheral Fatigue After High-Intensity and Low-Intensity Exercise in Men

Black, CD, Haskins, KR, Bemben, MG, and Larson, RD. Carbohydrate mouth rinsing does not alter central or peripheral fatigue after high-intensity and low-intensity exercise in men. J Strength Cond Res 36(1): 142-148, 2022-Carbohydrate (CHO) mouth rinsing improves performance during endurance exercise. However, its ability to attenuate fatigue during strength-based exercise is less certain. This study sought to determine the effects of a CHO mouth rinse on torque production and voluntary activation (VA%) after high-intensity and low-intensity isometric exercise. Twelve male subjects (22.5 +/- 2.3 years; 183.5 +/- 6.5 cm; 82.2 +/- 13.9 kg) completed 4 testing sessions in a double-blind crossover fashion. Knee extension maximal voluntary isometric strength (MVC) was assessed before(Pre), immediately (iPost-Ex), and 5 minutes (5-min Post Ex) after isometric exercise performed at 80% or 20% of MVC. An 8% CHO solution or placebo (PLA) was rinsed for 20 seconds after exercise. VA% was determined by twitch interpolation. A 2 condition (CHO vs. PLA) x 2 contraction intensity (20 vs. 80%) x 3 time (Pre, iPost Ex, and 5-min Post Ex) completely within subject-repeated measured analysis of variance was performed; statistical significance was set at p <= 0.05. Greater reductions in MVC were found at iPost-Ex after exercise at 20% compared with 80% of MVC (-25 +/- 14% vs. -11 +/- 8%; p < 0.001) as well as for VA% (-17 +/- 14% vs. -8 +/- 14%; p < 0.004). No differences were observed in the CHO vs. PLA condition (p >= 0.34). We were successful in eliciting differing levels of central and peripheral fatigue by exercising at a low and high intensity. Despite significantly larger declines in VA% after exercise at 20% of MVC, CHO mouth rinsing had no effects compared with placebo on any measured variable.