Decker K. P., M. J. Saunders, N. D. Luden, C. J. Womack, and N. J. Hladick. Mouth Exposure to Carbohydrate Prior to Exercise Possibly Impairs the Efficacy of Carbohydrate Mouth Rinsing during Exercise. Purpose: Carbohydrate mouth-rinsing (CHO-MR) during intense endurance exercise has been associated with improved cycling performance, due to neurological influences. However, prior studies have reported the efficacy of CHO-MR is attenuated following a pre-exercise meal. To determine if this outcome is related to desensitization of CHO receptors (rather than metabolic effects following digestion), this study will investigate whether CHO-MR prior to exercise influences cycling performance when CHO-MR is also used during exercise. Methods: Eight trained cyclists (age, 24 ± 6 yr; height, 176 ± 6 cm; weight 75 ± 12 kg; VO2max, 61 ± 8 ml/kg/min) completed three exercise trials, each consisting of 15-min of incremental, constant-load exercise followed by a simulated 30-km time-trial (TT). Treatment beverages in the trials were randomly counterbalanced: a) PL_PL: placebo before and during exercise, b) PL_CHO: placebo pre-exercise, CHO-MR during exercise, and c) R_CHO: CHO-MR before and during exercise. Physiological responses (VO2, VE, RER, RPE, heart rate, blood glucose and lactate) were assessed during constant-load exercise and during the TT. Magnitude-based qualitative inferences were used to evaluate differences in responses between treatments. Results: TT performance was ‘possibly’ impaired (59% likelihood) with R_CHO (57.3 ± 3.6) versus PL_CHO (56.9 ± 3.0 min). Both trials were ‘likely’ slower than PL_PL (55.8 ± 3.1 min), but the reliability of performance data from this trial may have been impacted by measurement error, which limited our ability to determine the influence of CHO-MR during exercise. Physiological responses between treatments during constant-load cycling, and the TT were generally similar between all treatments. Conclusion: A pre-exercise CHO-MR had a possibly negative impact on cycling performance that also included CHO-MR during exercise. Although further evidence is required to validate this finding, our data suggests that desensitization of CHO receptors related to recent CHO exposure may be partially responsible for previous reports that the efficacy of CHO-MR during exercise are attenuated by pre-exercise feedings. Keywords: CYCLING, CARBOHYDRATE, MOUTH-RINSING, PERFORMANCE, ERGOGENIC-AIDS
