Heart rate training can be very useful for runners hoping to train more effectively by helping us to avoid those dreaded junk miles. Heart rate monitors can be purchased as chest straps and some GPS watches now even have built-in optical sensors on the wrist.

Since I’ve been training with heart-rate for quite a few years myself, and as an ambassador for Suunto, I often get asked about training with heart-rate. I’ve also realized in talking with people that there’s quite a bit of confusion on how heart rate can and can’t be used.

Here are 5 common mistakes that runners make when training with heart rate.

1. Using Formulas to Calculate Heart Rate

When heart-rate based training was first popularized, many runners began using formulas such as subtracting their age from 220 to approximate their maximum heart rate, and to then calculate their zones based on percentages of this maximum. This formula assumes a similar profile for all athletes and, in my experience at least, can be so far off as to be useless.

Another method for approximating target heart rates zones is to perform various time trials, such as a 30-minute simulated race to determine your anaerobic threshold. These tend to be a little more accurate and may suffice for runners looking to get started with heart rate training, although relying on perceived effort alone has its caveats as heart rate is less reliable at higher intensities and can vary from day to day, as we’ll explore further below.

I’m very lucky to have the luxury of training with the Peak Centre for Human Performance in Vancouver where I regularly have VO2max and lactate threshold tests performed. These tests are more accurately able to determine a runner’s specific aerobic threshold, anaerobic threshold, and Vo2max, and to track changes over time with heart rate correlated to more concrete indicators like blood lactate levels.

2. Not Re-Testing Often Enough

If your thresholds and zones aren’t going to change over time, then what’s the point of training with heart rate in the first place?

Not only is heart rate data specific to an individual athlete, it can change drastically over time. I often see a jump in my thresholds following several weeks of speed work, so re-testing allows me to set new targets to ensure that I continue to improve. Conversely, after recovering from a big race or taking some time off from structured training, I rely on fresh data so that I can get back up to speed as quickly as possible through targeted training.

Comparative results over the years.

Comparative results over the years.

Whether you’re testing yourself on a track or getting tested in the lab, it’s important to get new data as often as at least a few times per year before and during active training.

3. Relying on Heart Rate During Races

As powerful a tool it is for training, heart rate is not a helpful indicator for performance nor should it be relied upon during a race. Many factors can affect heart rate throughout the day, including caffeine, hydration, temperature, stress, sleep, and (especially during a race) adrenaline.

When it comes to road races, most runners have a pretty specific time goal. It simply wouldn’t make sense to throw that out the window because your heart rate seemed a little high on that day, nor would it be wise to speed up just because it’s reading low.

Trail runners especially must understand that heart rate is subject to something called cardiac lag, meaning that you might not realize you’re pushing too hard on a hill until you’ve already crested it, and ultra runners shouldn’t be running anywhere near the top of their aerobic thresholds anyway which they should be able to do by feel come race day.

There’s nothing wrong with using heart rate as yet another data point during a race, but it’s often best simply ignored until our post-race analysis on Strava.

4. Using Heart Rate During Speed Work

Heart rate is a lagging indicator of stress, and many athletes like myself have what’s referred to as a ‘squished’ profile, with very narrow ranges of upper Zones stacked on a very large aerobic base. These two factors, combined with the variability of heart rate from day-to-day discussed above, make it almost useless when it comes to interval work.

Speed Work for Ultra Runners

As we begin training in Zone 3 and above, we should rely on pace targets or track lap times instead. Fortunately, this information is also typically provided as part of the detailed VO2max and lactate threshold tests done in a lab, or can be somewhat reliably estimated based on time trials or recent race results.

5. Comparing Heart Rate Data with Others

The main reason why common formulas for estimating heart rate fail is because of how different each and every one of our profiles are as athletes. You may be able to benchmark your own data to track trends over time, but it’s completely useless to compare your numbers against those of your friends or competitors.

Have you made any of these mistakes? What’s your experience with heart rate-based training? Tell me about it in the comments below!