Heart Rate Reserve

Heart rate reserve is the difference between maximum heart rate and resting heart rate. It is the basis of the Karvonen formula for training zones.

Definition

“Heart rate reserve” (HRR) is the difference between maximum heart rate and resting heart rate. It describes the range available to the cardiovascular system between complete rest and maximal exertion.

HRR = HRmax − HRrest

Training intensities can be expressed as a percentage of heart rate reserve (%HRR). Converting to a target heart rate uses the Karvonen formula:

target HR = HRrest + (%HRR × HRR)

Why it matters

Plain percentages of maximum heart rate ignore the resting heart rate. Two athletes with the same HRmax of 190 bpm but resting values of 42 and 65 bpm have completely different intensity ranges. At “70 % HRmax” both land at 133 bpm, although that is easy for one and already moderate intensity for the other.

Heart rate reserve accounts for this individual range. Percentages of HRR also correlate more closely with percentages of VO2 reserve than percentages of HRmax do, which makes them the better basis for intensity prescriptions.

Intensity	%HRR	Typical description
Recovery	40–50 %	Very easy, conversation effortless
Base	50–65 %	Aerobic range, long sessions
Tempo	65–80 %	Brisk, breathing clearly elevated
Threshold	80–90 %	Close to the anaerobic threshold
VO2max	90–100 %	Short intervals, near maximum

The table is a guide. Only a performance diagnostic shows where the individual thresholds actually lie.

How obseed measures it

obseed calculates heart rate reserve from the HRmax and HRrest values stored in the performance parameters. Resting heart rate should be measured lying down after waking; maximum heart rate should ideally come from a diagnostic test or a maximal effort, not from the “220 minus age” formula.

In training analysis, the intensity of a session can be shown both in beats per minute and as a percentage of HRR. This allows an assessment relative to the cardiovascular potential actually available rather than by absolute numbers.

Example

An athlete has an HRmax of 188 bpm and an HRrest of 48 bpm.

HRR = 188 − 48 = 140 bpm

For a base session at 60 % HRR:

target HR = 48 + (0.60 × 140) = 48 + 84 = 132 bpm

Using the simple HRmax method, 60 % would be 113 bpm, a difference of 19 beats. If the athlete runs the session at an average of 139 bpm, that corresponds to:

%HRR = (139 − 48) / 140 = 65 %

The session was at the upper edge of the base range.

References

Karvonen, M. J., Kentala, E., Mustala, O. (1957). The effects of training on heart rate: a longitudinal study. Annales Medicinae Experimentalis et Biologiae Fenniae.
Swain, D. P., Leutholtz, B. C. (1997). Heart rate reserve is equivalent to %VO2 reserve, not to %VO2max. Medicine and Science in Sports and Exercise.