No dose-response effect of carbohydrate mouth rinse concentration on 5 km running performance in recreational athletes

Oral carbohydrate rinsing has been demonstrated to provide beneficial effects on exercise performance of durations of up to one hour, albeit predominately in a laboratory setting. The aim of the present study was to investigate the effects of different concentrations of carbohydrate solution mouth-rinse on 5 km running performance. Fifteen healthy men (n=9; mean±SD age: 42±10 years; height: 177.6±6.1 cm; body mass: 73.9±8.9 kg) and women (n=6; mean±SD age: 43±9 years; height: 166.5±4.1 cm; body mass: 65.7±6.8 kg) performed a 5 km running time trial on a track on four separate occasions. Immediately before starting the time trial and then after each 1 km, subjects rinsed 25 mL of either 0, 3, 6, or 12% maltodextrin for 10 s. Mouth-rinsing with 0, 3, 6 or 12% maltodextrin did not have a significant effect on the time to complete the time trial (0%: 26:34±4:07 min:sec; 3%: 27:17±4:33 min:sec; 6%: 27:05±3:52 min:sec; 12%: 26:47±4.31 min:sec; P=0.071; 2 P  =0.15), heart rate (P=0.095; 2 P  =0.16), rating of perceived exertion (RPE) (P=0.195; 2 P  =0.11), blood glucose (P=0.920; 2 P  =0.01) and blood lactate concentration (P=0.831; 2 P  =0.02), with only non-significant trivial to small differences between concentrations. Results of this study suggest that carbohydrate mouth-rinsing provides no ergogenic advantage over that of an acaloric placebo (0%), and that there is no dose-response relationship between carbohydrate solution concentration and 5 km track running performance.