Related Experiment Video
Updated: Mar 16, 2026
08:45
Assessment of Physical Activity Intensity with Accelerometers and Oxygen Consumption
Published on: June 20, 2025
689
An Activity Index for Raw Accelerometry Data and Its Comparison with Other Activity Metrics
Jiawei Bai1, Chongzhi Di2, Luo Xiao3
1Department of Biostatistics, Johns Hopkins University, Baltimore, Maryland, United States of America.
Plos One
|August 12, 2016
Summary
A new Physical Activity Index (AI) summarizes accelerometer data better than traditional Activity Counts (AC) and ENMO. AI accurately measures sedentary to vigorous physical activity, especially in older adults.
Area of Science:
- Biomedical Engineering
- Public Health
- Gerontology
Background:
- Accelerometers are common in public health studies, collecting high-resolution data.
- Current summarized metrics like Activity Count (AC) lack transparent formulas and vary by device.
- This limits accurate interpretation and comparability of physical activity data.
Purpose of the Study:
- To introduce a novel metric, the Physical Activity Index (AI), for summarizing raw tri-axial accelerometry data.
- To compare the AI with existing metrics (AC and ENMO) against energy expenditure.
- To evaluate the sensitivity of AI, AC, and ENMO across different physical activity intensities.
Main Methods:
- Data from 194 women (60-91 years) performing 9 lifestyle activities were used.
- Tri-axial accelerometers (ActiGraph GT3X+) and portable calorimeters (Oxycon) were employed.
- Raw accelerometry data were converted into AI, AC, and ENMO; oxygen uptake was measured in METs.
Main Results:
- AI and ENMO showed higher sensitivity for moderate to vigorous activities than AC.
- AI demonstrated superior sensitivity for sedentary and light activities compared to ENMO.
- AI achieved the highest coefficient of determination for METs (0.72) and outperformed AC and ENMO in classifying physical activity intensity.
Conclusions:
- The proposed Physical Activity Index (AI) offers a transparent and effective method for summarizing accelerometry data.
- AI serves as a valuable alternative to AC, particularly for studies involving older adults.
- AI's enhanced sensitivity in detecting sedentary and light activities provides a significant advantage in geriatric research.
Related Concept Videos
01:12Measuring Acceleration Due to Gravity
1.4K
Consider a coffee mug hanging on a hook in a pantry. If the mug gets knocked, it oscillates back and forth like a pendulum until the oscillations die out.
A simple pendulum can be described as a point mass and a string. Meanwhile, a physical pendulum is any object whose oscillations are similar to a simple pendulum, but cannot be modeled as a point mass on a string because its mass is distributed over a larger area. The behavior of a physical pendulum can be modeled using the principles of...
A simple pendulum can be described as a point mass and a string. Meanwhile, a physical pendulum is any object whose oscillations are similar to a simple pendulum, but cannot be modeled as a point mass on a string because its mass is distributed over a larger area. The behavior of a physical pendulum can be modeled using the principles of...
1.4K
01:30Average Acceleration
15.7K
The importance of understanding acceleration spans our day-to-day experiences, as well as the vast reaches of outer space and the tiny world of subatomic physics. In everyday conversation, to accelerate means to speed up. For instance, we are familiar with the acceleration of our car; the harder we apply our foot to the gas pedal, the faster we accelerate. The greater the acceleration, the greater the change in velocity over a given time. Acceleration is widely seen in experimental physics. In...
15.7K
01:17Factors Affecting Activity Coefficient
1.8K
The extended Debye-Hückel equation indicates that the activity coefficient of an ion in an aqueous solution at 25°C depends on three partially interdependent properties: the ionic strength of the solution, the charge of the ion, and the ion size.
The activity coefficient value for an ion is close to one when the solution has almost zero ionic strength, i.e., when the solution shows close to ideal behavior. As the ionic strength of the solution increases from 0 to 0.1 mol/L, a...
The activity coefficient value for an ion is close to one when the solution has almost zero ionic strength, i.e., when the solution shows close to ideal behavior. As the ionic strength of the solution increases from 0 to 0.1 mol/L, a...
1.8K
01:10Relative Motion Analysis - Acceleration
1.0K
A slider-crank mechanism converts rotational motion from the crank into linear motion of the slider or vice versa. This mechanism consists of three main parts: the crank, the connecting rod, and the slider. The movement of the slider-crank is an example of general plane motion as the fluctuating angle between the crank and the connecting rod. Consider a segment AB where point A is at the end of the slider and point B is on the diametrically opposite end to point A, on a crack. The variance in...
1.0K
01:22Relative Motion Analysis using Rotating Axes - Acceleration
957
Consider a component AB undergoing a linear motion. Along with a linear motion, point B also rotates around point A. To comprehend this complex movement, position vectors for both points A and B are established using a stationary reference frame. The absolute velocity of point B is determined by adding the absolute velocity of point A, the relative velocity of point B in the rotating frame, and the effects caused by the angular velocity within the rotating frame.
Time differentiation is...
Time differentiation is...
957