Heart Rate Reserve

Heart rate reserve is the difference between resting heart rate (RHR) and  maximum heart rate (MHR). As an individual has a lower resting heart rate, functional heart reserve goes up. The importance of a lower heart rate becomes evident when calculating heart rate reserves.

• Example: Person A and B are both 20 years old.
  
  Person A -- RHR =  75 bpm; MHR = 220 - 20 = 200 bpm; HRR = 200 - 75 = 125 bpm.
  
  Person B -- RHR = 40 bpm; MHR = 220 - 20 = 200 bpm; HRR = 200 - 40 = 160 bpm

Percentage of Heart rate reserves is calculated by using the Karvonen Formula:

KEY Formula Variables:
-- Maximum Heart Rate (MHR)
-- Resting Heart Rate (RHR)
-- Percentage of Heart Reserve (%)

The Formula:

Target HR = ((MHR - RHR) * %) + RHR
or
Target HR = (((220-age) - RHR) * %) + RHR

To calculate 70% of Heart Rate Reserve (HRR) for a 20 year old with a Resting Heart Rate of 75 bpm, you would:

• Multi-step Process:
  • MHR = 220 - 20 = 200
  • RHR = 75
  • ((200 - 75) * 70%) + 75 = 162.5

OR

• Single Step or Compact Method:
  • (((220-20) - 75) * .7) + 75 = 162.5

Other Variation of the Karvonen Formula:

To calculate Percentage Intensity when given a Target Heart Rate for a given person:

% Intensity = (THR - RHR)/(MHR - RHR)               **THR = Target Heart Rate**

Example: For a 20 year old with a 50 bpm RHR exercising at a 150 bpm Target Heart Rate

% Intensity = (150 - 50)/(200 - 50) = .67 or 67% of Heart Rate Reserve or also considered VO₂max