The effect of hydration status on the measurement of lean tissue mass by dual-energy X-ray absorptiometry
Athletes cycle between exercise and recovery. Exercise invokes changes in total body water from thermal sweating, muscle and hepatic glycogen depletion and metabolic water loss. Recovery from exercise results in rehydration, substrate repletion, and possible glycogen supercompensation. Such changes may corrupt the measurement of hydrated tissues, such as lean tissue mass (LTM), by dual-energy X-ray absorptiometry (DXA). The purpose of this study was to determine the effect of exercise and thermal dehydration and subsequent glycogen supercompensation on DXA-based measurement of body composition.
Twelve active adult (18–29 years) males exercised at 70% VO2max on a cycle ergometer in a thermal environment (30 °C) to induce a 2.5% reduction in body mass. Participants subsequently underwent a glycogen supercompensation phase, whereby a high carbohydrate diet (8–12 g/kg body mass/day) was consumed for a 48-h period. Whole-body DXA measurement was performed at baseline, following exercise and supercompensation.
Following exercise, mean body mass decreased by −1.93 kg (95% CI −2.3, −1.5), while total LTM decreased by −1.69 kg (−2.4, −1.0). Supercompensation induced a mean body mass increase of 2.53 kg (2.0, 3.1) and a total LTM increase of 2.36 kg (1.8, 2.9). No change in total fat mass or bone mineral content was observed at any timepoint.
Training regimens that typically induce dehydration and nutrition regimens that involve carbohydrate loading can result in apparent changes to LTM measurement by DXA. Accurate measurement of LTM in athletes requires strict observation of hydration and glycogen status to prevent manipulation of results.
KeywordsDXA Hydration Lean tissue mass Measurement Glycogen Athletes
Analysis of variance
Body mass index
Bone mineral content
Bone mineral density
Dual-energy X-ray absorptiometry
Lean tissue mass
Least significant change
Physical activity readiness questionnaire
Region of interest
Total body water
Maximal oxygen uptake
The authors wish to acknowledge the assistance of Conor Hurley, Ross McGlynn, and Alexandra Cremona with data collection.
Compliance with ethical standards
All procedures performed involving human participants were in accordance with the ethical standards of the institutional research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
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