We live in a data-hungry world. Fancy watches and gadgets are the norm now for runners of any age and the data that comes with them is overwhelming! If you’re like me, you don’t want to let this precious information go to waste. One such metric is heart rate – more specifically, the number of times your heart beats in a minute.
Entire training systems have been developed around heart rate. Some athletes will swear by its effectiveness, while others stick their noses up at it. I’ve seen both sides of the coin in my own training, so I hope to give you an honest unbiased evaluation of how to train using a heart rate monitor and its limitations.
Zone Training
The concept behind heart rate training is based on five training zones. To train effectively, we should hit these zones enough times to make our body adapt. The five zones can be determined by, you guessed it, your heart rate! I’ll get in to the numbers and percentages in a second but here’s the zones that will help our conversation.
Zone 1 – (<80% of LTHR, <70% of Max Heart Rate) Uhh, are we even exercising?
This zone hardly constitutes exercising. You may even pass it by just briskly walking.
Zone 2 – (81-90% LTHR, 70-76% MHR) Easy aerobic running.
This is the bread and butter for any race that requires the aerobic system (spoiler alert: they ALL do!). At this intensity, the muscles will start to adapt at the cellular level, giving them more endurance-focused characteristics. It’s in this zone that the heart becomes more and more efficient at pumping blood, thus reducing the amount of heart beats (aka: effort) that is needed for a particular effort. In Matt Fitzgerald’s book, 80/20 Running, he suggests that roughly 80% of a runner’s weekly volume be made up of this type of running! Many elite athletes’ training logs will reflect this as well! Example workouts: easy days, recovery jogs in between intervals. Total Suggested Weekly Volume: 40-50%.
Zone 3 – (90-95% LTHR, 77-85% of MHR) The gray area.
The benefits of this zone are a cross between Zone 4 and Zone 2, but neither really get worked WELL when training in this zone. When you hear people make the case that runners run their easy runs TOO HARD, they are really saying that they have ventured from Zone 2 to Zone 3, which is making their workout less effective. For added benefits, stick to zone 2 or zone 4 and stay out of this zone 3. Example workouts: Marathon-paced runs, some long runs. Total Suggested Weekly Volume: 15-20%
Zone 4 – (96-100% LTHR, 86-90% of MHR) Now it’s getting serious.
This is a key zone to work to improve one’s lactate threshold, which builds strength and speed. In other words, you can endure faster paces for longer – and who doesn’t want that! I often describe this zone as “comfortably hard” when talking to athletes. You’re running hard but you can sustain it. Example workouts: 2-3 mile repeats, tempo runs, end of long runs, some fartleks. Total Suggested Weekly Volume: 8-10%.
Zone 5 – (100+%, 91+% of MHR) Give it all you’ve got!
We can think of this zone as the end of a 5k race or for short interval workouts. You cannot sustain this for very long. Working in this zone is going to improve your VO2 max, which is essentially the max amount of oxygen your body can use at a particular time. Example workouts: Short intervals, end of long intervals, VO2 Max workouts. Total Suggested Weekly Volume: 5-10%
What is my Lactate Threshold Heart Rate (LTHR)?
I’m so glad you asked! When we are running easily, our lactate levels remain consistent. We produce some, clear it out, produce some more, clear it out. That’s why we can keep this pace relatively consistently.
When we start to run faster, our bodies can no longer clear the lactic acid from our blood as quickly as it is getting produced, and we will become fatigued more quickly. This point is called our Lactate Threshold. Our heart rate while running at this faster pace is called our Lactate Threshold Heart Rate (LTHR).
It is slightly more accurate than simply max heart rate for developing heart rate training zones because two people can have the same max heart rate but wildly different thresholds. Our lactate threshold will improve over time with training, while our max heart rate will be fixed. The problem? It’s more difficult to find!
Here’s a test you can do: Run a 30 minute time trial on a flat course. 30 minutes. As fast as you can go! Your average heart rate for the last 20 minutes of this run is your lactate threshold heart rate (LTHR). I’ve used this multiple times and believe in its results.
Ok, now that we’ve cleared that up!
How Does Heart Rate Training Help?
Our heart rate can tell us effectively what training zone we are in while we are running. We may THINK we are running easy on our easy days, but slap a heart rate monitor on and you may find that you are well into zone 3 (ie: TOO FAST!). Easy days are where I see the most benefit of heart rate training because so much of my weekly volume (sometimes over 80% as stated above) is easy running. That’s a major chunk to be running too fast!
Your heart rate can be a gauge for you on tempo runs as well. These can be difficult runs for many athletes because they tend to race them. Let’s use a 30-minute tempo run as an example. “Runner A” who is racing it may spend that middle 10 minutes in zone 4 but blow through it for the last 10 minutes. As opposed to Runner B who sticks with the appropriate paces and spends at least 20 minutes in the right zone.
Who is going to get the better adaptation from that workout? Runner B, of course, for TWO reasons. First, they obviously spent more time in zone 4 working to raise their lactate threshold and improving strength and speed as discussed above. But ALSO, because they are not going to be as tired as Runner A who may have sabotaged the next workout because they are too fatigued!
Remember the goal with training: Do the LEAST amount of work as possible that will get you the desired benefit.
Beware the Drawbacks
Heart rate training has its fair share of detractors as well. As far as I can tell, the criticisms come down to these three:
- It’s not an accurate measure of effort. Heart rate can be affected by many things like sleep, stress, dehydration, and the weather. A bad night’s sleep can shoot my heart rate up at least 2-4 bpm the next day. But does my easy effort really have to slow by 30 seconds per mile as well? I’m not sure! But these are potential sticking points you’ll encounter. Furthermore, heart rate monitors are not always accurate themselves, so be aware of this when placing too much faith in yours.
- It doesn’t say your heart rate on your finishing time. Most of us set goals based on a finishing TIME. We don’t set goals of “I want to finish my half marathon with an average heart rate of 165” for example! If you’re heart rate is unexpectedly high on race day, you want to know that you can still hit your pace and perform.
- We are more than just physiology! While many elite athletes have unbelievable physiological factors (high lactate threshold, high VO2 max, low resting heart rate, etc.), it is not always the runner with the best stats that wins the race! If it were, races would be much more predictable. Racing is more than just a physical activity. There’s a neurological and emotional aspect to it as well. Training strictly by zones misses this point and can make runners think they are more limited by those things than they really are.
Part 2 | Another Approach
Some heart rate enthusiasts subscribe to a different approach in heart rate training, popularized by Phil Maffetone. While similar to what is above, I want to do it justice so I’m saving it for Part 2 of this article! Stay tuned!
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