Heart Rate Reserve

Heart rate reserve describes the difference between a measured heart rate or the predicted maximum heart rate and the resting heart rate in a person. It indicates the heart rate reserve cardiovascular fitness of a person.

How to calculate heart rate reserve

The formula used to calculate the heart rate reserve is HRR = HRmax − HRrest.

As the heart rate reserve increases the HRrest has to drop. This is a beneficial parameter that is calculated by athletes to increase their performance.

Heart rate and oxygen consumption

Heart rate has a relation with oxygen consumption especially when intensities rise to reach ranges between 50-90% VO2 max. Thus exercise intensity is the percentage of maximum heart rate (calculated using the formula 220 – age).

A 30 year old who has a maximum heart rate of 190bpm thus may train up to 75% of his intensity at 143bpm.

The earlier formula “220 – age” makes no allowances for variations in resting heart rate among individuals.

The formula for heart rate reserve allows a better target heart rate to be determined for optimum training capacity based on both maximum and resting heart rate.

Calculating Target Heart Rate with Karvonen Formula

  • 220 – age = maximum heart rate
  • Maximum heart rate – resting heart rate = heart rate reserve
  • (Heart rate reserve X training%) + resting heart rate

Comparing the two formulas

To compare the two formulas, an example of a 45 year old man who has a resting heart rate of 60 beats per minute and who wants to train at 70% maximum is assessed.

Target heart rate in this individual:-

220 – 45 = 175 beats per minute. This is the maximum heart rate.

According to Karvonen formula (115 x 0.7) + 60 = 140.5

Thus 140.5 beats per minute is the target heart rate using this method.

Using the traditional 220 age formula this same person would have a target heart rate of (220-45 X 0.7) or 122.5

122.5 beats per minute is considerably lower than that estimated by the Karvonen formula.


  1. www.mpc.edu/…/Heart%20Rate%20Reserve.pdf
  2. http://www.rbht.nhs.uk/patients/condition/heart/
  3. www.uhs.nhs.uk/…/Bradyarrhythmias-patientinformation.pdf
  4. www.uhs.nhs.uk/…/Tachyarrhythmias-patientinformation.pdf
  5. http://serendip.brynmawr.edu/sci_edu/waldron/pdf/HeartRateProtocol.pdf
  6. knowledgetranslation.ca/…/Ref%20ID%208067-20090628231006.pdf

Further Reading

  • All Heart Rate Content
  • What is Heart Rate?
  • Target Heart Rate
  • Heart Rate Abnormalities

Last Updated: Jun 4, 2019

Written by

Dr. Ananya Mandal

Dr. Ananya Mandal is a doctor by profession, lecturer by vocation and a medical writer by passion. She specialized in Clinical Pharmacology after her bachelor's (MBBS). For her, health communication is not just writing complicated reviews for professionals but making medical knowledge understandable and available to the general public as well.

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