Doubly-Labeled Water PDF Print E-mail
The use of doubly-labeled water to assess free-living energy expenditure is currently regarded as the gold standard technique.  With a reported precision of ± 3%, this method serves as a reference for validating other instruments or methods designed to measure energy expenditure.  

Doubly-labeled water is a noninvasive procedure involving the ingestion of a quantity of water labeled with a known concentration of naturally occurring, stable isotopes of hydrogen and oxygen.  As energy is expended in the body, carbon dioxide and water are produced, and the differences between the isotope elimination rates are used to calculate total energy expenditure.  This method can be carried out on a wide range of individuals over lengthy time periods, usually between 4 and 21 days, which is advantageous for capturing habitual energy expenditure patterns.  However, the cost of materials and expertise required to analyze the isotope concentrations via mass spectrometry prohibits the use of doubly-labeled water in large epidemiological studies.


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Tools for Subjective Measurement

Self-report measures are the most common approach to quantifying physical activity levels and patterns in free-living adult populations.  The three main types of subjective instruments are recall questionnaires, physical activity logs, and physical activity diaries.  Individual data obtained from self-report measures are typically converted into estimates, which allow researchers to categorize or rank individuals or populations by physical activity level. 

Environmental Measures

Tools for Objective Measurement

Accurate assessments of the physical activity dimensions (type, duration, frequency, intensity) and contexts (sport or recreation, occupation, transportation, incidental) requires an instrument that objectively quantifies activities performed in free-living conditions.
  • Measurements of Heart Health and Capability Using EKG
  • Indirect Calorimetry at Any Workload in the Laboratory or the Field
  • Bone Health and Osteoporosis Risk Assessment Using DXA Technology
  • Body Composition, Including Regional Fat and Lean Mass, Using DXA Technology
  • Balance Testing of Visual, Somatosensory, and Vestibular Systems Independently and in Combination
  • Functional Movement Screens

Platforms for Research

  • Mobile Phones & PDAs
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