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Mapping the Body's Response to Exercise

Some research doesn't offer much practical information for the general public. But it does expand our knowledge of how the body works. Some day, this knowledge may help us take better care of ourselves.

This is one of those studies. Researchers in Japan used positron emission tomography (PET) to study how the body burns energy at rest and during exercise. PET technology involves using radioactive tracers that show up on a special kind of film. Doctors and scientists use PET tests to measure the activity, or metabolism, of tissues in the body. Tissues that show a high uptake of the radioactive tracers are very active, with a high metabolism.

The authors divided 12 healthy men into two groups. One group sat quietly in a comfortable chair for 35 minutes. The other group ran for 35 minutes, stopping only to have the radioactive tracer injected into their bloodstream. Both groups then had whole-body PET scans.

Researchers found that the active tissues in the resting group were the heart, the brain, and the organs in the abdomen, including the intestines, liver, and kidneys. The running group had markedly different PET scans. The scan showed a much higher uptake in the leg and heart muscles. There was much less activity in the abdominal organs. Only the brain showed the same metabolic activity, whether running or at rest.

So what does this mean for you? Nothing right now. But it provides a fascinating glimpse of how our bodies adjust to the demands we place on them.

References: M. Iemitsu, et al. Whole-Body Energy Mapping Under Physical Exercise Using Positron Emission Tomography. In Medicine & Science in Sports & Exercise. December 2000. Vol. 32. No. 12. Pp. 2067-2070.

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