Physical activity assessment by accelerometry in people with heart failure

Area of Science:

• Cardiology
• Exercise Physiology
• Biomedical Engineering

Background:

• International physical activity guidelines recommend at least 150 minutes of moderate-to-vigorous physical activity (MVPA) weekly for adults, including those with cardiac conditions.
• Accurate categorization of accelerometer data into behaviorally relevant intensity metrics, especially for chronic disease populations like heart failure (HF), remains a challenge.
• Existing physical activity intensity thresholds are primarily based on healthy adults and may not accurately reflect the energy expenditure of HF patients.

Purpose of the Study:

• To establish specific acceleration values for inactivity and MVPA during daily living activities in heart failure (HF) patients.
• To calibrate these values using oxygen consumption (VO2) measurements.
• To compare the derived HF-specific thresholds with commonly used intensity thresholds established for healthy adults.

Main Methods:

• Twenty-two adults with HF performed daily living activities while wearing wrist- and hip-worn accelerometers and undergoing indirect calorimetry for VO2 measurement.
• Raw accelerometer data was converted to milligravity (mg), and energy expenditure was calculated in METs (metabolic equivalents).
• Activity intensity thresholds were determined using multilevel mixed effects linear regression and receiver operator characteristic curve analysis, with cross-validation via a leave-one-out method.

Main Results:

• Accelerometer values for inactivity (<1.5 METs) and MVPA (≥3.0 METs) in HF patients were over 50% lower than previously published thresholds for both wrist and waist accelerometers.
• Specific inactivity thresholds ranged from 16.7 to 18.6 mg (vs. 45.8 mg for healthy adults), and MVPA thresholds ranged from 43.1 to 49.0 mg (vs. 93.2 to 100 mg for healthy adults).
• Measured METs in HF patients were significantly higher than standard and predicted METs across standing and walking activities.

Conclusions:

• Heart failure (HF) specific accelerometer intensity thresholds for inactivity and MVPA are substantially lower than those derived from healthy populations.
• These differences are attributed to a lower resting metabolic rate and increased energy expenditure during daily activities in HF patients.
• The findings necessitate revised physical activity intensity thresholds for accurately assessing and prescribing exercise in individuals with heart failure.