From The Inside Triathlon Archives: Getting To The Core

  • By Aaron Hersh
  • Published Feb 10, 2012
  • Updated Oct 31, 2014 at 4:37 PM UTC
Photo: John Segesta

The Tool
To find out what Alexander must do to stave off dehydration and overheating, Steinmetz needed to know Alexander’s core temperature and dehydration level at various points throughout the key workouts of his six-day Kona training camp. Both athlete and advisor agreed that Alexander should not hold himself to a strict hydration strategy during the race. They were not trying to find the perfect recipe. Rather, they wanted to come up with a set of guidelines for how to minimize dehydration.

To get Alexander’s true core temperature, an under-the-tongue thermometer just wasn’t going to cut it. Instead, Steinmetz turned to something called the ingestible thermal monitoring system (ITMS). The monitoring system, developed by NASA and Johns Hopkins University scientists, is a two-part system made of a capsule, which is swallowed, and a handheld data reader called the CorTemp data recorder. The three-quarter-inch-long capsule contains a quartz crystal temperature sensor that measures core temperature, a battery and a wireless transmitter that sends a signal through the body to the data recorder. Temperature is measured by holding the recorder up to Alexander’s lower back, near where the ingested monitoring system is sitting.

To test Alexander’s dehydration level, Steinmetz turned to a less sophisticated tool: a bathroom scale. Any weight lost during one of the camp’s training sessions was assumed to be water lost from sweating.

RELATED: Training Day With Craig Alexander

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Aaron Hersh

Aaron Hersh

Aaron Hersh is the Senior Tech Editor of Triathlete magazine. To submit a question, write Aaron at

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