Receptors in the mouth in influencing exercise performance

[Guest guest]

>

> The Route to Obesity Passes Through Your Tongue

>

> obesity, taste, taste buds, sugar, bitter, tongue, leptin,

> insulinAccording to neuroscientists, obesity gradually numbs the

taste

> sensation of rats to sweet foods, and drives them to consume larger

> and sweeter meals. There is apparently a critical link between taste

> and body weight.

>

> Previous studies have suggested that obese persons are less

sensitive

> to sweet taste, but little is known about the specific differences

in

> sense of taste between obese and lean individuals. Researchers

> investigated these differences by studying the taste responses of

two

> strains of rats.

>

> Compared to the lean and healthy LETO rats, the taste responses in

> OLETF rats mirror those in obese humans. These rats tend to

> chronically overeat due to a missing satiety signal, and they become

> obese and develop diabetes. The obese rats also show an increased

> preference for sweet foods.

>

> The researchers implanted electrodes in the rodents' brains to

record

> the firing of nerve cells when the rats' tongues were exposed to

> various tastes. The OLETF rats had about 50 percent fewer neurons

> firing when their tongues were exposed to sucrose, suggesting that

> obese rats are overall less sensitive to sucrose.

*****

The below may be of interest:

The effect of carbohydrate mouth rinse on 1-h cycle time trial

performance.

JM, Jeukendrup AE, DA.

Med Sci Sports Exerc. 2004 Dec;36(12):2107-11. Links

PURPOSE AND METHOD: To investigate the possible role of carbohydrate

(CHO) receptors in the mouth in influencing exercise performance,

seven male and two female endurance cyclists (VO(2max) 63.2 +/- 2.7

(mean +/- SE) mL.kg*(-1).min(-1)) completed two performance trials in

which they had to accomplish a set amount of work as quickly as

possible (914 +/- 40 kJ). On one occasion a 6.4% maltodextrin

solution (CHO) was rinsed around the mouth for every 12.5% of the

trial completed. On the other occasion, water (PLA) was rinsed.

Subjects were not allowed to swallow either the CHO solution or

water, and each mouthful was spat out after a 5-s rinse.

RESULTS: Performance time was significantly improved with CHO

compared with PLA (59.57 +/- 1.50 min vs 61.37 +/- 1.56 min,

respectively, P = 0.011). This improvement resulted in a

significantly higher average power output during the CHO compared

with the PLA trial (259 +/- 16 W and 252 +/- 16 W, respectively, P =

0.003). There were no differences in heart rate or rating of

perceived exertion (RPE) between the two trials (P > 0.05).

CONCLUSION: The results demonstrate that carbohydrate mouth rinse has

a positive effect on 1-h time trial performance. The mechanism

responsible for the improvement in high-intensity exercise

performance with exogenous carbohydrate appears to involve an

increase in central drive or motivation rather than having any

metabolic cause. The nature and role of putative CHO receptors in the

mouth warrants further investigation.

=========================

Mouth rinse but not ingestion of a carbohydrate solution improves 1-h

cycle time trial performance.

Scand J Med Sci Sports. 2008 Nov 3. [Epub ahead of print] Links

Pottier A, Bouckaert J, Gilis W, Roels T, Derave W.

The aim of the present study was to further explore the influence of

ingestion and mouth rinse with a carbohydrate-electrolyte solution

(CES) on the performance during a approximately 1 h high-intensity

time trial on trained subjects. Subjects rinsed around the mouth or

ingested a 6% isotonic CES or placebo (14 mL/kg body weight) before

and throughout a time trial in which they had to accomplish a set

amount of work (975+/-85 kJ) as quickly as possible.

In the mouth rinse conditions, time to complete the test was shorter

(P=0.02) with CES (61.7+/-5.1 min) than with placebo (64.1+/-6.5

min), whereas in the ingestion conditions, there was no difference

between placebo (62.5+/-6.9 min) and CES (63.2+/-6.9 min). Although

power output and lactate concentration during exercise were

significantly higher when subjects rinsed their mouth with CES

compared with placebo, the rating of perceived exertion values did

not differ. Blood glucose concentration increased after ingestion of

but not after mouth rinse with CES.

The interesting finding of the present study is that rinsing the

mouth with but not ingestion of CES resulted in improved performance.

=========================

Ross Tucker and Dugas recently posted the below on their

website:

http://www.sportsscientists.com/search?updated-max=2008-11-27T11%3A58%

3A00%2B02%3A00 & max-results=6

Firstly, this study did NOT show that rinsing the mouth is better

than swallowing the solution. It simply compared rinsing with CHO to

rinsing with H2O. It is not, therefore, an excuse not to drink

glucose-containing drinks during exercise! (the second study

discusses this a bit more).

However, what it does do is help us understand how shorter exercise

might be improved by carbohydrates. The authors of this study

speculated that there are receptors in the mouth, which are

stimulated by the CHO-drink (but not by water), and then trigger

centres in the brain that then increase the central drive for

exercise. Once again, this would suggest that the brain picks up

the " reduction " in effort as a result of the glucose in the mouth,

and the cyclist rides harder, with the result that the perception

increases to the desired level at a higher overall performance level.

It supports the notion that the sensation and perception are the

regulators of performance.

===================

Carruthers

Wakefield, UK