Physical activity and human energy expenditure

Area of Science:

• Exercise Physiology
• Human Movement Science
• Biomedical Measurement

Background:

• Accurate measurement of physical activity in daily life is crucial for understanding health and energy expenditure.
• Doubly labelled water (DLW) is the gold standard for validating field-based physical activity assessment methods.
• Accelerometry offers objective and precise measurement of activity patterns, including frequency, duration, and intensity.

Purpose of the Study:

• To review methods for measuring physical activity in daily life, focusing on DLW and accelerometry.
• To illustrate the applications of DLW and accelerometry in assessing physical activity limits and energy expenditure.
• To examine the role of activity intensity in determining the overall physical activity level.

Main Methods:

• Review of literature on doubly labelled water method for energy expenditure measurement.
• Review of literature on accelerometry for assessing physical activity patterns.
• Analysis of data on physical activity index and its determinants.

Main Results:

• The upper limit of the physical activity index is confirmed to be 2.5.
• Exercise training combined with energy restriction or in elderly subjects did not increase the physical activity index.
• In children, low and high-intensity activities determine the physical activity index, while in adults, moderate-intensity activities are the primary determinant.

Conclusions:

• In adults, the physical activity level is primarily determined by the distribution of low and moderate-intensity activities.
• High-intensity activities have a limited impact on daily energy expenditure.
• Increasing activity energy expenditure does not necessarily require high-intensity activities.