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Potential errors in body composition as estimated by whole body scintillation counting
The Journal of Laboratory and Clinical Medicine
|April 1, 1983
Summary
Vigorous exercise may falsely elevate apparent potassium-40 levels due to radon progeny interference. This study demonstrates that radon progeny, not increased potassium, accounts for higher gamma ray counts after exercise, impacting body composition measurements.
Area of Science:
- Nuclear medicine
- Human physiology
- Environmental health
Background:
- Whole body counting of potassium-40 (40K) is used to estimate lean body mass.
- Previous reports suggest vigorous exercise increases apparent 40K content in athletes.
- The cause of this observed increase requires further investigation.
Purpose of the Study:
- To investigate whether the reported increase in apparent 40K content after exercise is a true physiological change or an artifact.
- To evaluate the influence of environmental factors, specifically radon and its progeny, on 40K measurements.
Main Methods:
- Three cyclists and one nonathlete underwent exercise protocols.
- Whole body gamma ray scintillation counting was used to measure 40K.
- Measurements were taken before and after exercise, with the nonathlete exposed to a radon source.
Main Results:
- Apparent 40K content increased in the athletes' thighs and the nonathlete's whole body post-exercise.
- Counts for 214Bi, a radon progeny, also increased significantly.
- A strong correlation (r = 0.87) was found between 40K and 214Bi counts, with the increase attributed to 214Bi gamma emissions.
Conclusions:
- The apparent increase in 40K after exercise is an artifact caused by radon progeny.
- Failure to account for radon progeny leads to significant errors in lean body mass estimation using 40K counting.
- Environmental radon contamination must be considered in whole body counting studies.