Abs hold the secret to sweating it out

29 May 2014

A University of Sydney study has uncovered new temperature sensors in the abdominal area of the body that are responsible for independently altering our sweat output.

The discovery was made as part a larger program of research investigating the impact of ingesting hot versus cold fluids when exercising.

"We were able to prove that cold drinks don't always have the cooling effect that people anticipate when exercising in a hot environment and in doing so also uncovered new internal sensors within the body which were responding to the temperature of the ingested fluid" said Dr Ollie Jay from the Faculty of Health Sciences.

Known as thermoreceptors - these internal sensors which are stimulated by changes in temperature - appear to be located not in the mouth or throat as many originally thought, but further along the gastrointestinal tract.

While previous studies had suggested that cold and warm fluid ingestion had an impact on whole body sweat loss, no previous research could pinpoint the timing, or specific skin or body location of such changes.

Dr Jay's study design allowed this discovery by comparing the results of those who consumed the hot and cold fluids orally, swirling it around in their mouth only, and those who had it injected directly into their stomach via a nasogastric tube while exercising.

The results showed large decreases in sweating when the cold fluid was injected directly into the stomach, but no such changes were seen when mouth-swilling cold water.

These findings suggest that the sensors responsible are located in the abdominal area.
It also showed that when exercising in the heat a cold drink causes an immediate suspension of sweating - the key way in which our bodies cool down.

"The heat that our body loses to warm up the cold drink after it is ingested in countered by the fact that the body decreases the heat that we lose through sweating," Dr Jay said.

"So you may feel cooler for having had a cold drink, but in reality the body's core and skin temperatures are the same as when ingesting a body temperature drink."

The study is published in the current edition of the Journal of Applied Physiology.

Contact: Michelle Blowes

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