HR monitors

Heart rate is an indicator of the physiological response to PA
- Moderate to vigorous PA: linear relationship between HR and oxygen consumption
- Lower intensities and rest: non-linear
  - Confounded by e.g. caffeine, stress, smoking, temperature, …
Outcomes
- Heart rate bpm (average, min, max)
- Energy expenditure (EE) (subject/group derived regression equations)
Placement
- Classic HR belt + watch
- Wrist worn: optical sensors -> consumer devices
  - photoplethysmography
Pros
- lightweight and portable
- relatively cheap
- minute-by-minute data collection (time pattern)
Cons
- Confounding factors of HR – VO2 relationship
  - Temperature, humidity, hydration, stress, age, gender, muscle mass
- Individual calibration of HR – VO2 relationship required
  - Implications for large-scale studies
- Not suited for low intensity EE estimation
- Discomfort of chest strap
Single electrocardiogram
- Example: Apple watch