How hard should your exercise be?

How to calculate your cardio exercise intensity

First, regardless of what the calculations tell you, always use how you feel as the primary guide to intensity. Unless you are training for athletic events and at maximum intensity, you should never be so out of breath that you can’t have a conversation (moderately labored breathing with conversation is fine, especially if your walk takes you up a hill).

It is smart and recommended to have a physical before initiating a new exercise regimen especially if you are over 40 or if you have any risk factors such as high blood pressure, diabetes or elevated cholesterol to name a few.

Always perform a 3-5 minute warm-up before exercise and a 3-5 minute cool-down afterward.

Now, back to calculating heart rate intensity for your cardio or HIIT exercise programs.

First you have to calculate your Maximum Heart Rate (MHR) in beats per minute. You could get your max heart rate tested maybe at a university performance lab or with an athletic performance center but it is not fun. Basically you are hooked up to an EKG or other heart rate monitoring device and you begin walking on a treadmill. Every 2-3 minutes, the incline and the speed is increased. At each stage, your Heart Rate will increase to meet the new demand of more incline and more speed. At some point, when you are at full exertion, almost falling off the treadmill, and barely keeping up, your heart rate will not increase when the speed and incline are increased. This is the point at which your ability to keep up the pace is about over and you have reached your max heart rate. It is painful and in some cases can cause injury (for example, falling on the treadmill or passing out) so I recommend just calculating your MHR.

Fortunately, exercise scientists have used a lot of test subjects performing many treadmill tests and have developed calculations so that smart people like you can just do a calculation and forego the treadmill max test.  I recommend using the Heart Rate Reserve method because it takes into account your resting heart rate.

With this method, you calculate your Max Heart Rate (MHR) by subtracting your age from 220. So, a 40 year old would have an estimated MHR of 180 beats per minute, (220-40= 180).

Next you need to take your resting heart rate (RHR). I recommend a seated heart rate. The best time to do this is in the morning before you start your day. If you just wake up and maybe go to the bathroom or brush your teeth, once finished, go sit in a comfortable chair or on the side of the bed for about 5 minutes. Once you are back in a rested state, take your pulse at your wrist for a minute. If you do not know how to take your pulse, you can learn pretty fast.

Taking your pulse: I prefer taking a pulse at the wrist and I usually use my left. To do this I rest my left arm on a chair arm or pillow and with my elbow bent, turn the left arm palm up. I take my index finger and middle finger on my right hand and place them on the thumb side of my left wrist in the space between the bone and the first tendon that I feel. This is over the radial artery. You should feel the pulse and it may take moving your fingers on the right hand around a little bit over this space before you find it. Do not press too hard, just mild pressure is all that is needed to find it.

Once you find your pulse, start a stop watch and count it for a full minute (or at least 30 seconds and just multiply by 2). Be careful not to count the seconds, just the pulse. I usually try to prevent this by just checking the time every few seconds.

Let’s say your resting heart rate (RHR) is 74.

The next step is to calculate your Heart Rate Reserve (HRR). you do this by subtracting your RHR from your MHR. See this: MHR-RHR=HRR.

In our example it would be 180-74=106

The next step is to adjust your intensity by taking a percentages of your HRR. If you are just a beginner and want to start with moderate intensity, take 40% and 60% of your HRR and you add back in your Resting Heart Rate (RHR). If you want to start with a higher intensity, use 60% and 80% of the HRR and add back in your RHR.  

First let’s take the percentages.

40% of 106=42 and 60% of 106 = 63 and 80% of 106= 85.

There are a couple of steps left so don’t leave yet.

All you have to do now is add back in your resting heart rate (RHR) to get your Target Heart Rate Range.

For moderate intensity add 42 + 106 = 148 beats per minute to 63 + 106 = 169 beats per minute. So your estimated training heart rate range would be 148-169 beats per minute. You can use a heart rate monitor to set your range and notify you if you go to low or too high. Also use how you feel.

For vigorous intensity it would be 63+106 = 169 beats per minute to 85 + 106 = 191 beats per minute.

This range would be 169 beats per minute to 191. Now remember, as you age, your predicted Max Heart Rate decreases so your training range changes over time as well.

If you do not have a heart rate watch, fitbit or other device that records your heart rate, all you have to do is stop for about 15 seconds every few minutes to get an idea where your pulse range is.

Take your pulse manually for 15 seconds and then just do the math in your head and multiply by 4 or for 30 seconds and multiply by 2. Stopping for 15-30 seconds every little while will not affect your routine negatively.

If you are not currently taking your heart rate, it is good practice and it also helps you get better at just going by how you feel (your perceived exertion) during exercise and to get better at managing your intensity.

Now, it is recommended that you get 30 min of moderate exercise 5 days per week in your Target Heart Rate Range. The good thing is that you can break this up into 2 or more sessions. I would recommend two, 15 minute sessions. And what is even better is that if you do not have time for 30 minutes in a day, do what you can. Let’s say you average 15 min a day for 5 days. That is 75 more minutes than you are currently getting. That is very good and it is much better than doing nothing.

go out and have a great workout today. Be glad that you accomplished something very good for you.