Methods to assess physical activity with special reference to motion sensors and accelerometers

Area of Science:

• Biomedical Engineering
• Sports Science
• Wearable Technology

Background:

• Motion sensors are crucial for assessing physical activity levels.
• The evolution from mechanical pedometers to electronic accelerometers has advanced measurement capabilities.
• Accurate assessment of physical activity in free-living conditions is essential for health monitoring.

Purpose of the Study:

• To review the evolution of motion sensors for physical activity assessment.
• To evaluate the reliability of a three-directional electronic accelerometer for physical activity monitoring.
• To compare bench test results with real-world performance in subjects.

Main Methods:

• Review of motion sensor technology, focusing on accelerometers.
• Intrainstrument and interinstrument variation testing of a three-directional accelerometer.
• Treadmill experiments to assess reproducibility at different speeds (3, 5, and 7 km/h).

Main Results:

• Intrainstrument variation in bench tests was below 8%.
• Interinstrument variation during treadmill experiments averaged 22%, uncorrected by bench tests.
• Reproducibility on treadmills was high (76-95%) across tested speeds.

Conclusions:

• Electronic accelerometers are promising for physical activity assessment in free-living settings.
• Significant interinstrument variation exists, questioning current reliability and bench test relevance.
• Further investigation is needed to understand and improve accelerometer reliability for outdoor applications.