Failure to generalize determinants of self-reported physical activity to a motion sensor

Area of Science:

• Behavioral Science
• Exercise Physiology
• Psychology

Background:

• Accurate assessment of physical activity is crucial for understanding its psychological determinants.
• Discrepancies exist between self-report and objective measures of physical activity.

Purpose of the Study:

• To investigate if psychological predictors of physical activity differ based on assessment method (electromechanical vs. self-report).

Main Methods:

• 44 young adults completed questionnaires on outcome expectancies, perceived barriers, and self-efficacy.
• Physical activity was monitored for 7 days using both a daily diary (self-report) and a Caltrac motion sensor (objective).
• Canonical correlation analysis was used to examine relationships between psychological variables and physical activity measures.

Main Results:

• Psychological variables (outcome expectancies/perceived barriers and self-efficacy) significantly predicted physical activity measured by the 7-day diary (explaining 26% of variation).
• These psychological variables were not significantly related to physical activity measured by the Caltrac motion sensor.
• Outcome expectancies/perceived barriers showed a moderate correlation with both diary (r=0.51) and Caltrac (r=0.34) measures.

Conclusions:

• Psychological determinants of physical activity are better predicted by self-report measures than by objective motion sensor data in this population.
• The choice of physical activity assessment method significantly influences the observed relationship between psychological factors and actual behavior.