Heart rate is a useful tool to predict fitness level and quantify physical effort. Based on the linear relationship between heart rate and VO2 heart rate can be used as an effective gauge to guide exercise intensity. Heart rate training intensities can be used to establish training zones to improve cardiorespiratory fitness.

Maximum heart rate (MHR) is used to formulate exercise training intensities or target heart rates (THR). The classic method for obtaining maximum heart rate is an estimation based on an individual’s age subtracted from 220. For example the estimated MHR for a 20 year old would be 200 (220 – Age (20 years) = 200 beats ∙ min^-1). Target training zones for aerobic training using the Heart Rate Max Formula would be 70% for the lower limit and 90% upper limit of the MHR. This method does have draw backs; one in particular is the physiological factors associated with age and how it affects heart rate. A second is the standard deviation of 10-12 beats. Individuals that are one or two standard deviations from the norm (32% of the population) will require additional criteria to help improve the accuracy of the prediction. RPE and submax test response can both be used to aid in validity of the training zone predictions.

In addition to the aforementioned concerns related to prediction the Heart Rate Max formula loses greater value with individuals under 20 year old and persons over 60 year old. Children and older adults have different factors influencing their resting and maximum heart rates that need to be considered. Children have higher resting heart rates that progressively decrease with age into adolescences. Their heart rates are increased due the smaller heart size, decreased stroke volume and decreased blood volume. Explaining why (220 – age) is inaccurate for this population. The changes in resting heart rate skew their maximum heart rate prediction.

Physiological systems also change with age altering the maximum heart rate of seniors. These changes include decreases in blood plasma, stroke volume, cardiac muscle and heart volume, stimulation and activation of the heart which decrease MHR. The efficiency and contractibility of the older heart creates a lower MHR. These changes are exaggerated with inactivity.

Research conducted by Tanaka, Monahan, and Seals found that [208 – (0.7 x Age)] is a more accurate formula for these populations. The formula leads to a more accurate maximum heart rate estimation that accounts for age related variations. The formula gives values that are 6 beats per minute lower for the under 20 year old populations and 6 beats per minute higher for the over 60 year population increasing the accuracy of the prediction. The physiological changes are factored into the equation creating a more appropriate tool. The standard deviations of both the traditional and modified formulas are consistent; 10 beats per minute due individual differences.