New MET Data Types

Two new heart-rate-based intensity metrics join MET and MVPA, giving researchers and health programs a more complete view of physical activity.

Fitrockr has extended its data model with two new intensity metrics: HRI-MET and Keytel-MET. They sit alongside the existing MET and MVPA values and are available for all connected wearables.

Why more than one intensity metric?

MET stands for Metabolic Equivalent of Task. It’s a unit that expresses the energy cost of an activity relative to resting metabolism.

1 MET is the energy you use sitting quietly, roughly 1 kcal per kg of body weight per hour (about 3.5 ml O₂ per kg per minute).

Light activity (slow walking, desk work) is below 3 METs.

Moderate activity (brisk walking, easy cycling) is 3 to 6 METs.

Vigorous activity (running, fast cycling) is above 6 METs.

As per definition above, MET requires participant weight information to be known and maintained during data collection. If this information is not available, alternative MET calculations can be of interest, such as HRI-MET and Keytel-MET. 

What is new

HRI-MET is based on the Heart Rate Index method, which estimates metabolic equivalents from the ratio of exercise heart rate to resting heart rate. Because it is normalized to the individual’s own resting heart rate, it accounts for differences in baseline fitness and needs no additional inputs such as weight or sex. That makes it a practical choice for large, heterogeneous cohorts.

Keytel-MET is based on the Keytel et al. regression equations, which estimate energy expenditure from heart rate, age, sex, and body weight. Fitrockr converts the result into MET values, so it can be compared directly with the other metrics on the platform. It is well suited to programs where personal profile data is available and a more individualized estimate is wanted.

Read more at Fitrockr MET & MVPA.

How it fits with MET and MVPA

MET remains the vendor-reported or motion-based intensity value.

MVPA continues to show moderate-to-vigorous activity minutes, the basis for most public health guidelines.

HRI-MET and Keytel-MET add two independent, heart-rate-derived views of the same activity.

Together, they let you cross-check results, compare devices on a common footing, and choose the method that best fits your protocol instead of depending on a single vendor’s algorithm.

What this means for your organization

Researchers can report intensity using published, citable methods and run sensitivity analyses across metrics.

Clinical and healthcare teams get a physiologically grounded measure of effort, not only movement.

Coaches and gamification programs can base challenges and goals on intensity that reflects real exertion.

Availability

The new metrics are available in the Daily/Hourly/Detailed Health Log downloads for all subscriptions.