Carbohydrate mouth rinse is no more effective than placebo on running endurance of dehydrated and heat acclimated athletes

• Published in: European journal of applied physiology Vol. 123; no. 7; pp. 1507 - 1518
• Main Authors: Kamaruddin, Harris Kamal, Farah, Nor M. F., Aziz, Abdul Rashid, Mündel, Toby, Che Muhamed, Ahmad Munir
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.07.2023; Springer Nature B.V
• Subjects: Aerobic capacity; Arousal; Biomedical and Life Sciences; Biomedicine; Blood flow; Carbohydrates; Heart rate; Heat; Human Physiology; Mouthwashes; Occupational Medicine/Industrial Medicine; Original Article; Placebos; Relative humidity; Sports Medicine; Endurance; Mouth rinse; Heat stress; Treadmill; Dextrose
• ISSN: 1439-6319; 1439-6327
• DOI: 10.1007/s00421-023-05170-y

Purpose To determine whether carbohydrate mouth rinsing would improve endurance running performance of tropical natives in a warm-humid (30 °C and 70% relative humidity) environment. Method Twelve endurance male runners [age 25 ± 3 years; peak aerobic capacity ( V ˙ O 2peak ) 57.6 ± 3.6 mL . kg −1 . min −1 ] completed three time-to-exhaustion (TTE) trials at ~ 70% V ˙ O 2peak while swilling 25 ml of a 6% carbohydrate (CHO) or taste-matched placebo (PLA) as well as no mouth rinse performed in the control (CON) trial. Results TTE performance was significantly longer in both CHO and PLA trials when compared with the CON trial (54.7 ± 5.4 and 53.6 ± 5.1 vs. 48.4 ± 3.6 min, respectively; p  < 0.001 and p  = 0.012, respectively), but was not significantly different between CHO and PLA trials ( p  = 1.000). The rating of perceived exertion was not different between the CHO and PLA trials, however, was significantly affected when compared to the CON trial ( p  < 0.001). A similar effect was observed for perceived arousal level between the CHO and PLA trials to the CON trial. Core temperature, mean skin temperature and skin blood flow were not significantly different between the three trials (all p  > 0.05). Similarly, plasma lactate and glucose as well as exercise heart rate were not influenced by the trials. Conclusions The present study demonstrates that mouth rinsing, whether carbohydrate or placebo, provides an ergogenic benefit to running endurance when compared to CON in a heat stress environment. Nevertheless, the results do not support the notion that rinsing a carbohydrate solution provides a greater advantage as previously described among non-heat acclimated individuals within a temperate condition.