Taste of power goes to the head, then muscles

Just a swish of carbs can boost energy

Gargling Gatorade could clinch the gold for future Olympians. A new study establishes a neural link between mouth and muscles that slips right past the gut, producing additional power output with nothing more than the promise of an impending nutritional boost.

“What we’ve uncovered is a way in which we can shortcut our sensory circuitry, and to fool our body, maybe, briefly, into thinking the tank is full,” says study coauthor Nicholas Gant of the University of Auckland in New Zealand. The study will appear in an upcoming issue of Brain Research.

Earlier studies had shown that swishing and spitting an energy drink made study subjects sprint or cycle faster than swishing a placebo — even though the sugar never made it to the muscles. This effect could be the brain’s signal to the body that “help is on the way, fuel is in the mouth,” Gant says. But scientists weren’t sure whether there is a neural pathway that goes directly from the taste buds to the muscles, or if it’s all in athletes’ heads.

To find evidence of a mouth-to-muscle pathway, Gant and colleagues had 16 healthy men between the ages of 21 and 36 flex their biceps while electrodes on their arms measured the electrical energy in their muscles.

After wearing out their biceps for 11 minutes, the participants swished and swallowed a bright green Gatorade-like beverage sweetened with an artificial sugar called acesulfame K. In half the trials, the drink also contained a colorless, flavorless carbohydrate called maltodextrin.

Not surprisingly, the men’s muscles perked up in response to carbs. But measurements of their blood sugar at four-minute intervals showed that the response began even before the nutrition entered the men’s systems.

The electrical energy in the muscles of athletes who drank the maltodextrin-containing drink increased by 30 percent, and the maximum amount of force they exerted went up by 2 percent. By contrast, the energy-free drink had no effect on muscle performance; maximum force actually went down by 3 percent as subjects who drank it got more tired.

“We were really surprised by the magnitude of increase in force production,” says Gant, whose research has been used to advise Olympic athletes. “It’s less than a percent of your total output that will decide whether you got the gold. We’re seeing improvements that are far greater than that.”

To see if the trick worked even if the subjects never swallowed and their muscles were fresh, the researchers asked 17 different participants to rinse their mouths with either the carb drink or the placebo. The researchers then measured the electrical energy in the participants’ hand muscles. Swishing the carb drink increased the muscular energy by 9 percent.

“This clearly shows that you change something in the brain which directly affects the muscle,” comments Asker Jeukendrup of the University of Birmingham in England. “It’s quite an important piece of the puzzle.”

To see which part of the brain was responsible, the researchers applied a magnetic jolt to the subjects’ scalps in both experiments to probe activity in the primary motor cortex, a region of the brain associated with planning and executing movements. Surprisingly, the extra electrical boost in the muscles did not come from the motor cortex. The signals may come from a deeper, less consciously controlled part of the brain, Gant suggests.

In addition to helping sprinters and shot-putters improve their game, these results could help develop physical therapy treatments for people who have trouble controlling their muscles, Jeukendrup speculates.

This study supports earlier evidence that the taste receptor for sweetness is different from the part of the mouth that detects carbohydrates. But “whatever that is, that has not been detected yet,” Jeukendrup says. “That’s definitely something that someone should do at some point, try to identify that.”

Lisa Grossman is the astronomy writer. She has a degree in astronomy from Cornell University and a graduate certificate in science writing from University of California, Santa Cruz. She lives near Boston.

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