Assessment of Physical Activity and Energy Expenditure

Assessment of physical activity and energy expenditure underpins our understanding of human movement, health and nutrition across the lifespan. Physical activity encompasses any skeletal muscle movement that expends energy, while energy expenditure quantifies the metabolic cost of such activity and basal physiological processes. Traditional gold-standard methods include doubly labelled water for free-living energy expenditure and indirect calorimetry for laboratory‐based measurement of oxygen consumption and carbon dioxide production. Advances in wearable technology have popularised accelerometry, heart rate monitoring and combined sensor platforms, enabling continuous, real-world tracking. These methods vary in complexity, accuracy and cost, from laboratory validation to large-scale population surveillance. Contemporary research explores device calibration, metric standardisation—such as the Metabolic Equivalent of Task (MET)—and the integration of ambient sensors with wearables. Accurate assessment informs public health guidelines, clinical interventions, occupational safety, sports science and nutrition policy, with global implications ranging from chronic disease prevention to addressing undernutrition in low- and middle-income settings.

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Assessment of Physical Activity and Energy Expenditure publication trend

The graph below shows the total number of articles in assessment of physical activity and energy expenditure across all publications each year (not limited to Nature Index journals).

Technical terms

Energy expenditure (EE): the amount of energy a person uses to perform bodily functions and physical activities, typically expressed in kilocalories or joules.

Metabolic Equivalent of Task (MET): a unit representing the ratio of metabolic rate during a specific activity to resting metabolic rate, where 1 MET is defined as the energy expended at rest.

Accelerometer: a wearable device that measures acceleration forces to infer movement patterns and activity intensity over time.

Indirect calorimetry: a method of estimating energy expenditure by measuring oxygen consumption and carbon dioxide production during respiration.

Resting Metabolic Rate (RMR): the rate of energy expenditure while at rest, reflecting the minimal energy required to maintain vital physiological functions.

References

1. Large Estimate Variations in Assessed Energy Expenditure and Physical Activity Levels during Active Virtual Reality Gaming: A Short Report. International Journal of Environmental Research and Public Health (2023).
2. Ambient and Wearable Sensor Technologies for Energy Expenditure Quantification of Ageing Adults. Sensors (2022).
3. Physical activity, time use, and food intakes of rural households in Ghana, India, and Nepal. Scientific Data (2020).