Physical activity assessment: comparison between movement registration and doubly labeled water method

Area of Science:

• Human physiology
• Metabolic research
• Biomedical engineering

Background:

• Accurate assessment of physical activity energy expenditure is crucial for understanding metabolic health.
• Traditional methods can be invasive or lack objectivity in real-world settings.
• The doubly labeled water method provides a gold standard for measuring average daily metabolic rate (ADMR).

Purpose of the Study:

• To evaluate the efficacy of a triaxial accelerometer for assessing physical activity under daily living conditions.
• To correlate accelerometer output with energy expenditure measured by the doubly labeled water method.
• To investigate physical activity levels across different body mass index (BMI) categories.

Main Methods:

• Employed the doubly labeled water method to determine ADMR in 16 men and 14 women.
• Utilized a triaxial accelerometer to register body movement over a 7-day period.
• Measured resting metabolic rate (RMR) in a respiration chamber (sleeping metabolic rate, SMR).
• Extended the study to include individuals with anorexia nervosa and morbid obesity.

Main Results:

• Accelerometer output (AO) significantly explained variations in ADMR after adjusting for SMR (R2 = 0.64).
• Average AO did not differ significantly between normal weight, anorexia nervosa, and morbidly obese groups.
• In anorexia nervosa, AO correlated significantly with BMI, indicating higher activity in those with BMI ≥ 17 kg/m2.
• Morbidly obese individuals showed distinct low and high activity level subgroups based on AO.

Conclusions:

• A triaxial accelerometer is an objective tool for quantifying physical activity energy expenditure.
• This method can effectively differentiate activity levels among individuals with varying BMIs.
• The findings support the use of accelerometers for objective physical activity assessment in diverse populations.