Cardiac reserve in physiology
The cardiac reserve is the heart's ability to increase its blood flow in one minute.
Compared to basal conditions, the human heart can increase its flow rate by 3-7 times, depending on age, state of health and degree of training. The maximum percentage increase in cardiac output (or range) compared to the baseline values (at rest) constitutes the cardiac reserve.
Reserve heart rate according to Karvonen
The Karvonen method is concerned with indirectly calculating the ideal heart rate of training or THR ( target heart rate ). Compared to the other indirect methods, that of the reserve heart rate is credited with the lower percentage of error.
Karvonen assumes that the resting heart rate differs from individual to individual and uses this data to establish a new benchmark, called the reserve heart rate. Then set the number of resting beats of the subject as zero, then calculate the training intensity percentage based on the difference between maximum heart rate and resting heart rate.
Cardiac reserve frequency (FCR) = max HR - rest HR
Therefore in a 30-year-old male subject, with an HR at rest of 70 bpm, the theoretical cardiac reserve is equal to:
220 - 30 (age) - 70 (HR at rest) = 120 bpm
At this point the range calculation to be checked / maintained during training is estimated as follows:
(% of reserve heart rate) + Freq. cardiac at rest
More generally:
THR = ((HRmax - HR at rest) ×% Intensity) + HR at rest
One of the advantages of backup heart rate is that for moderate to high work intensity, the percentage value of FCR is similar to the heart rate corresponding to a similar percentage of reserve of VO2max. Therefore, especially for a trained subject, it represents a much more accurate reference than the simple percentage of maximum heart rate.
Calclolo of the reserve heart rate
