Heart Rate Calorie Calculator — Study Reference

Keytel and colleagues fitted separate male and female group regressions for exercise energy expenditure. The entered group selects the paper's coefficients. It is a study category, not a measurement of anyone's metabolism.

Male group: kJ/min = −55.0969 + 0.6309 × heart rate + 0.1988 × weight in kg + 0.2017 × age. Female group: kJ/min = −20.4022 + 0.4472 × heart rate − 0.1263 × weight in kg + 0.074 × age. Divide kJ/min by 4.184 for kcal/min, then multiply by exercise minutes. The female weight term is negative in the published equation.

For a 30-year-old at 70 kg, 130 bpm and 30 minutes, the female group gives about 223.1 kcal; the male group gives about 336.2 kcal. These are two regression outputs, not personal measurements.

Source: Keytel et al., Journal of Sports Sciences (2005), author-uploaded full paper

This equation uses average heart rate as one predictor of expenditure during submaximal exercise. It does not calculate heart rate zones or establish a safe training range. For general intensity ranges based on estimated maximum heart rate, use the exercise intensity reference on this site.

The paper describes an approximately linear heart rate–energy relationship around 90–150 bpm during physical activity. This is modeling context, not a validated medical cutoff.

Source: Keytel et al., Journal of Sports Sciences (2005), author-uploaded full paper

The development sample included 115 regularly exercising adults aged 18–45 and weighing 47–120 kg. They completed steady treadmill or cycle stages. Use the worksheet for that educational context; exercise modes or populations outside it require other evidence.

The model without a fitness measurement explained 73.4% of variation in the development sample. That group-fit statistic does not mean any individual's calorie estimate is within a fixed percentage of measured expenditure. Heart rate and expenditure also vary with fitness and conditions.

Source: Keytel et al., Journal of Sports Sciences (2005), author-uploaded full paper

Use an average recorded during the steady exercise minutes being modeled, rather than a resting, peak, or whole-day heart rate. Enter only the minutes represented by that average; intervals with changing intensity are outside the simple constant-rate calculation.

The original study recorded heart rate and respiratory exchange during steady treadmill and cycle stages. An entered watch value does not reproduce that lab protocol.

Source: Keytel et al., Journal of Sports Sciences (2005), author-uploaded full paper

The worksheet makes the published regression and its unit conversion inspectable. It can illustrate how age, weight, heart rate, and the published group coefficients change a group estimate within the studied setting.

It does not determine a personal energy budget, prove exercise benefit, or substitute for a direct energy-expenditure measurement.

Source: Keytel et al., Journal of Sports Sciences (2005), author-uploaded full paper

Why are there two regression groups? The paper fitted different coefficients for participants classified male and female. Select the equation you intend to examine; the two values are not interchangeable or an averaged default.

Why is an average above 150 bpm excluded? The paper describes approximate linearity near 90–150 bpm. The input restriction avoids displaying this linear model as though it were established beyond that context; it is not advice to stop exercise at 150 bpm.

Does the total include a warm-up? Only if its minutes and average rate are represented by the steady input. The model does not separately calculate a changing warm-up.

Source: Keytel et al., Journal of Sports Sciences (2005), author-uploaded full paper