Target Heart Rate: Worthless?

by Rich Rojas

Not long ago, before a severe heat wave struck our region, I got together with a few of my co-workers to play tennis one evening after work. I really love to play tennis even though I’ve never progressed beyond the intermediate “hacker” level.

I do have a few brief flashes of what appears to be a game, but that’s usually overshadowed by a host of botched shots, which I like to refer to as “unforced errors.”

The temperature was in the low 80s and the average age of my colleagues is around 30. At 49, I’m the senior citizen in the group, but I felt I could hang with them.

I’m not sure if it was the heat or being out of condition, but after about 20 minutes I had to excuse myself and take a breather. I really didn’t feel very good and I didn’t want to take any chances, but after a 5-minute rest I caught my second wind and played for another hour and a half.

I felt somewhat embarrassed because my co-workers know how fanatical I am about running off to the gym at lunchtime to workout. It also hit home that maybe I’m not in very good cardio-vascular shape! It really made me rethink my training regimen.

My first thought was maybe all this emphasis on staying in the “fat-burning” heart rate zone was really just a false sense of complacency. Maybe what I really needed to be doing was getting my heart rate up much higher and working on improving my cardio conditioning. At least this would be the best way to improve my stamina on the tennis court.

The other harsh reality is that all this so-called “fat burning” training wasn’t really burning very much fat!

Coincidentally, I recently came across an article that discussed a book entitled “The Heart Rate Monitor Guidebook” by Sally Edwards. She states, “The ‘220 minus your age’ formula is worthless.” She advises that you determine your maximum heart by using the “Sub-Max Step Test”.

This simple test is performed by stepping up and down on an 8-inch step for 3 minutes without pausing and then taking your heart rate during the third minute. I just did this test today at the gym. I used one of those step aerobic platforms, which works great by the way.

Once you have your heart rate, she then advises that you add an “estimate factor” to it based on your fitness level:

Poor shape = 55
Average shape = 65
Excellent shape = 75

You then take 70% – 80% of this number to get your fat-burning target heart rate.

My results from the step test were:

144 bpm at the end of 3 minutes
144 + 65 (assume average shape) = 209 bpm
.70 * 209 = 146 bpm (target fat-burning heart rate)

80% would be 167 bpm, which quite frankly I think would kill me. She advises not to go over 90%. Don’t worry Sally, there’s no chance of that happening!

Please be very careful when performing this test as well as calculating your sub-max heart rate. As you can see, this number will most likely be substantially higher than the old method:

200 – 49 = 171 bpm
.70 * 171 = 120 bpm

What it looks like to me is that this sub-max method actually puts your fat-burning heart rate closer to your cardio-conditioning heart rate derived with the old method. This seems to make sense. Highly conditioned athletes in sports such as basketball usually aren’t carry around a lot of body fat!

So if you feel that your training and conditioning are at an intermediate to advanced level, you may want to take up the intensity of your workouts and see if the fat starts to melt away -- like I do on a hot summer evening while playing tennis!