Are pedometers adequate instruments for assessing energy expenditure?

Area of Science:

• Exercise Physiology
• Biomedical Engineering
• Obesity Research

Background:

• Accurate assessment of energy expenditure (EE) is crucial for obesity management.
• Daily step counts are a popular, practical method for evaluating physical activity (PA) in large populations.
• Limited data exists on the ability of pedometers to track EE in real-world settings.

Purpose of the Study:

• To evaluate the efficacy of pedometers (step counts) versus accelerometry in assessing 24-hour EE in healthy adults.
• To determine the primary determinants of EE, including body weight, height, and activity metrics.

Main Methods:

• Measured 24-hour EE using indirect calorimetry in a respiratory chamber for 71 healthy adults.
• Utilized two waist-worn accelerometers: one for step counting (ACC(STEP)) and another for whole-body acceleration (ACC(RMS)).

Main Results:

• Step counts (ACC(STEP)) did not correlate with PA-related EE (PAEE) or 24-hour EE.
• Body weight was the primary determinant of EE, explaining 30-75% of variance.
• Accelerometry signals (ACC(RMS)) explained 8% of PAEE variance after accounting for body weight; step counts did not.
• Body weight, height, and ACC(RMS) together predicted 83% of 24-hour EE variance.

Conclusions:

• Daily step counts are an inaccurate and crude predictor of EE and general PA.
• Accelerometry signals offer a more meaningful measure of EE than step counts, especially in sedentary individuals.
• Combined accelerometry, body weight, and height data provide a robust estimation of 24-hour EE.