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Related Experiment Video

Updated: Dec 19, 2025

Assessment of Physical Activity Intensity with Accelerometers and Oxygen Consumption

Assessment of Physical Activity Intensity with Accelerometers and Oxygen Consumption

Published on: June 20, 2025

No one accelerometer-based physical activity data collection protocol can fit all research questions.

Patrick Bergman¹, Maria Hagströmer^2,3,4

¹Department of medicine and optometry, eHealth Institute, Linnaeus University, 39182, Kalmar, Sweden. patrick.bergman@lnu.se.

BMC Medical Research Methodology

|June 5, 2020

Summary

Increasing sample size is more effective than longer measurement periods for reducing the Standard Error of the Mean (SEM) in physical activity research. This finding can improve the accuracy of accelerometer-based studies.

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A Method for Quantifying Upper Limb Performance in Daily Life Using Accelerometers

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Area of Science:

Exercise Physiology
Biostatistics
Wearable Technology

Background:

Accurate measurement of physical activity and sedentary behavior is crucial but challenging.
Minimizing the Standard Error of the Mean (SEM) is vital for statistical power in group comparisons.
Sample size and repeated observations per subject impact SEM.

Purpose of the Study:

To investigate how varying sample sizes and repeated observation periods affect SEM in accelerometer-based physical activity research.
To determine the most effective strategy for reducing SEM in such studies.

Main Methods:

A convenience sample wore accelerometers for 28 days.
Calculated SEM based on within- and between-subject variances for different combinations of sample sizes and measurement durations.

Main Results:

Increasing sample size significantly reduced SEM, regardless of physical activity intensity or protocol design.
Increasing the number of measurement days per subject yielded smaller reductions in SEM compared to increasing sample size.

Conclusions:

Larger sample sizes are more effective than longer individual measurement periods for reducing SEM.
Findings challenge current accelerometer research protocols, emphasizing the need to prioritize sample size for enhanced statistical power.