04 June 2021

Rinse Pink to Run

Welcome back. You may recall that, eight months ago, I blogged about a study that found rinsing with an antibacterial mouthwash after exercise reduced the blood-pressure lowering effect of exercise (Skip Mouthwash After Exercise). The study was led by an investigator from the UK.

Well, there’s another mouth-rinsing, exercise-related study by UK researchers. But that’s where the similarities end.

The recent study by researchers affiliated with the UK’s Loughborough College and University of Westminster examined the effect of a mouth rinse’s color on exercise performance. Although the study sample was small, the findings could be big, maybe a new avenue of future research in sports drinks and exercise.

Pick a mouth rinse for exercising, clear or pink.
Study Premise
The researchers began with recognition that a carbohydrate mouth rinse commonly produces a well-documented 2% to 3% benefit in running and cycling performance during exercise sessions up to 1 hour duration. A carbohydrate mouth rinse also activates the reward and motor function areas of the brain, improving pleasure, arousal and motor output during high-intensity or prolonged exercise.

The researchers also recognized that the consumption of food and drink is a multisensory experience, with color often manipulated to enhance taste perception and psychophysiological response. In that context, the perception of sweetness is enhanced if a food or drink product appears pink.

Given that the color pink is associated with sweetness and the expectation of sugar-carbohydrate intake, they reasoned that a pink-colored mouth rinse that had no carbohydrate might elicit a benefit similar to that of a carbohydrate mouth rinse through a placebo effect.

They then set out to determine if mouth rinsing with a pink, non-caloric, artificially sweetened solution could improve self-selected running speed and distance covered during a 30-min run.

Study Design and Execution
The researchers recruited 10 healthy volunteers (6 male, 4 female; age 30 ± 3 years) who regularly ran at least 3 times/week and were judged fit by a readiness questionnaire.

The participants visited the laboratory on three occasions (one preliminary and two experimental trials), each separated by one week. The experimental trials were randomized for each participant.

Preliminary Trial:  The participants watched a video that detailed the benefits of a carbohydrate mouth rinse and were informed that the study aimed to compare the effects of mouth rinsing two commercial sports drinks. The true aim of the study and rinse content were not disclosed until the study was completed.

The two rinses were prepared identically by adding 0.12-grams of pure sucralose to 500-milliliters of plain water. Two drops of non-caloric pink colorant were added to one rinse; the other remained clear.

After the video, the participants were given a full familiarization of the experimental protocol during which they were asked to rinse their mouth with unsweetened clear water.

Experimental Trials: Each experimental trial required participants to exercise on a motorized treadmill set at a gradient of 1.0%.

The trials included a warm-up (2-min walk, 10-min run) and a 30-min, self-paced running protocol. For the latter, participants were instructed to self-select the speed necessary to maintain a rating of perceived exertion (RPE) of 15 (hard/heavy).

During each trial, the participants rinsed for 5-seconds with 25-milliliters of one of the randomly assigned solutions on 9 occasions--4 during the warm-up, 5 during the 30-min run.

The researchers recorded the distance run and mean speed for the entire 30-min and at 5-min intervals. They also measured heart rate, felt arousal (6 point scale) and pleasure/displeasure (11 point bipolar scale) 30-seconds prior to each mouth rinse and on run completion. Following the second experimental trial, they interviewed the participants to determine perceived differences in distance covered and drink ratings between trials.

Distances (meters) and speeds (kilometers/hour) measured when running with a clear or pink mouth rinse. A and C: Bar charts show overall mean differences during the 30-minute run; dashed lines show individual responses; B and D: Lines and divisions show differences at 5-minute intervals (from www.frontiersin.org/articles/10.3389/fnut.2021.678105/full).
Wrap Up
Mouth rinsing with a pink non-caloric, artificially sweetened solution improved self-selected running speed and distance covered by 4.4% compared to rinsing with an isocaloric, taste-matched clear solution.

Heart rate and feelings of arousal were unaffected by mouth rinse color, yet feelings of pleasure increased by about 12% with the pink mouth rinse, which may have bolstered the performance improvement.

I hope you're feeling in the pink. Thanks for stopping by.

Study of mouth rinsing with pink solution in Frontiers in Nutrition journal: www.frontiersin.org/articles/10.3389/fnut.2021.678105/full
Article on study on EurekAlert! website: www.eurekalert.org/pub_releases/2021-05/uow-pdc051021.php

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