Can you use an equation to determine your max heart rate?
The most widely used equation to predict maximum heart rate (the highest heart rate that a person can achieve) is: Max Heart Rate = 220-Age in Years. For example, predicted maximum heart rate for a 20 year old would be 220 – 20 = 200 beats per minute. How accurate is that formula? Not very. Look at the graph below, which represents actual measured maximum heart rate (not estimated) versus age in years. If 220 – age were accurate, the dots (individual data points) would be on a straight line and would decline with age. Look at how much spread there is in the data. You can see that one 24 year old had a maximum heart rate of about 210 BPM and another had a maximum heart rate of about 165 BPM. If we used the equation (220-age) for both of these individuals to prescribe an exercise intensity, one of these individuals would be working impossibly hard, and the other hardly working at all.
A thorough review of the scientific research concerning the use of mathematical equations for estimation of maximum heart rate concluded that, “Currently, there is no acceptable method to estimate heart rate max.”
Does this mean that using heart rate to gauge exercise intensity is worthless? No. It is useful, but caution must be exercised in interpreting the numbers. If the session feels too hard, it probably is (and vice versa). A really hard interval session (i.e., Tabata protocol) or a sprint at the end of a shorter race (i.e. 1.5 mile or 5K) will generally get you within 5-7 BPM from your maximum heart rate.
Robergs, RA, and Landwehr R, The surprising history of the HRmax = 220 – age equation, Journal of Exercise Physiology (online), 5(2), 2002.