Comparative validity assessment of five activity monitors: does being a child matter?

Area of Science:

• Exercise Physiology
• Biomechanical Engineering

Background:

• Activity monitors are widely used to estimate energy expenditure during physical activity.
• Accurate prediction of energy expenditure is crucial for health and fitness monitoring.
• Existing models may not fully account for individual anthropometric and demographic variations.

Purpose of the Study:

• To investigate the impact of age and leg length on the accuracy of energy expenditure predictions from five activity monitors.
• To determine if incorporating age and leg length improves the validity of these predictions.

Main Methods:

• Eighty-six participants aged 8-40 years engaged in treadmill activities at speeds from 4 to 12 km/hr.
• Measured energy expenditure (VO2) was compared against predictions from five activity monitors.
• Analysis assessed differences in prediction accuracy across five leg length categories.

Main Results:

• Accelerometer counts or pedometer steps, combined with age, weight, and leg length, explained 85-94% of measured energy expenditure.
• Incorporating age and leg length as predictor variables significantly increased the explained variance in energy expenditure across all tested speeds.
• Leg length and age were identified as key factors influencing prediction accuracy.

Conclusions:

• Age and leg length significantly affect the validity of energy expenditure predictions from current activity monitors.
• Future activity monitor development and data analysis should control for age and leg length to enhance accuracy.
• Accurate physical activity energy expenditure estimation requires consideration of individual user characteristics.