Target Heart Rate

A reader (age 43) asked:

My heart rate is around 155-160 when I’m running a typical mile on treadmill. Should I slow down? My Dr. recommends HR of 130 till I can tolerate 170 6-9 months from now.

This is a common, though not very straight-forward issue. There are several contributing factors to what an individual’s target heart rate should be. For example, the traditional method of calculating Target Heart Rate is 60-90% of your Maximum Heart Rate. Maximum Heart Rate is calculated as 220 minus your age:

220 – age (in years)

for age 43 – 220 – 43 = 177

for age 31 – 220 – 31 = 189

for age 65 -220 – 65 = 155

Where does the calculation for Maximum Heart Rate come from? Good question – I had to look it up. There is a somewhat linear relationship between intensity of exercise and heart rate (i.e. the more intense you exercise, the faster your heart will beat) as established in a research study years ago. At some point, however, the heart rate is unable to continue increasing with increases in exertion – that point is deemed the Maximum Heart Rate. Rather than measuring that point in individuals, the above equation was derived in 1971 to provide a rough estimate of Maximum Heart Rate across all populations.

Subsequent research revealed that this equation is fraught with error, as there is incredible variety between individuals of the same age. I know I’ve been able to take my heart rate higher than my calculated Maximum HR. Revised formulas have been suggested:

205.8 – 0.685 (age)

for age 43 = 176

for age 31 = 184.5

for age 65 = 161

or

208 – 0.7(age)

for age 43 = 178

for age 31 = 186

for age 65 = 162.5

Though there’s not great disparity between these calculations, there may still be significant variation between seemingly similar individuals. Thus, it’s recommended to design exercise regimens to focus on other measurements of intensity rather than heart rate alone. For example, “perceived effort” is one option, though quite subjective. When I do HIIT on the elliptical, I just aim to give it almost all I can, aiming for 90-100% effort during the high-intensity intervals, then falling to roughly 50% effort between intervals.

A Target HR of 60-90% of Maximum Heart Rate is the standard recommendation for exercise intensity. Traditionally, a Target HR of 60-70% of Maximum HR has been suggested as optimal for fat-burning, but that is simply not true. As you will learn from my HIIT post, exercise of higher intensity is better for fat loss, but a beginner will not be able to handle that regimen right off the bat.

When starting out on a new exercise regimen from a relatively inactive lifestyle, it certainly makes sense to start out low and gradually ramp up the intensity. I recommend that you not get hung-up on the numbers so much as just doing the exercise. Work hard, and it will pay off over time. If you want to monitor your heart rate, that’s okay, but I don’t think it’s necessary let off the intensity of your workout just because you have exceeded your Target HR, unless you are pacing yourself for an endurance workout.

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