I recently listened to an inspiring episode of the Marathon Training Academy podcast named Understanding Heart Rate Training, in which co-host Angie explains all the heart rate zones and the training connected to them in an easy-to-understand way. I love their podcast btw.
Three different heart rate training methods were explained and one of them made most sense to me in terms of racing, and that’s the lactate threshold method.
It makes sense to me because the only way to get faster is to raise this threshold, which is the highest limit you can sustain without too much discomfort. So you run faster, for longer, right?
In other words, the lactate threshold is the limit at which the body can no longer clear the lactic acid because too much is being produced and not enough oxygen is there to clear it.
Here’s how it works: One starts jogging and no oxygen is used to produce energy during the first few seconds. Muscle glycogen (carbs) is used for energy, and lactic acid builds up.
As the body adapts and goes into aerobic mode, it starts using both glycogen and fat for energy. During lower impact activities the ratio between carbs and fat used is roughly 50/50. Oxygen clears the lactic acid, by sending it back in the bloodstream and in the liver, where some of it is converted back into glycogen.
If the pace increases, less and less fat is used for fuel. Although fat is a great source of energy, it is highly inefficient and it cannot be broken down fast enough when the demand is high. Muscle glycogen becomes the only source of energy and the lactic acid builds up again. It gets to a point when the oxygen cannot clear the lactic acid fast enough, and that is the threshold that one should watch out for. Apparently this threshold can be raised with training.
First of all I had to find out what my threshold was, so I listened to the episode again, and noted one test method: I had to jog 10 minutes as warm-up, then run at a fast pace for 30 minutes. The pace was supposed to be like a 5K pace, or in a scale from 1 to 10 an effort of 8.
Then I had to look into my heart rate monitor data and calculate the average heart rate for the last 20 minutes of the run. This was going to be my lactate threshold.
I’m not sure I got this right, I ran maybe a bit too fast. I had a result of 163 bpm, which is just as the one of the podcast’s co-host Angie. This cannot be right, she’s a pro! I had to try again.
So today I tried this test again but got the time wrong and stopped at 20 mins in, as opposed to the 30 mins I was meant to do.
The end result was roughly same though, with an average of 160 bpm in the last 10 minutes, and that would have probably drifted to 163 bpm with another 10 minutes at that pace.
I still doubt I have the same threshold as Angie, but 163 shall be for now.
Anyway, these are my zones calculated as a percentage of my lactate threshold:
Zone 1 – up to 80%
In my case up to 130 bpm, and it would be like slow jogging. This is where you burn most fat.
Zone 2 – 81-89%
For me 131-145 bpm. Apparently this is the golden zone for endurance training. I should stay in this zone for at least the first half of my marathon. Training in this zone builds the foundations.
Zone 3 – 90-95%
146-155 bpm. Running (not too fast) uphill, or when I’m pushing slightly harder than my marathon target pace. More carbs are broken down, than fat.
Zone 4 – 95-99%
156-161 bpm. This is the limit, and it should be reached only for short periods of time, like the faster parts during a repeats workout. I guess I could run a 10K in this zone.
I’ll leave Zone 5 to the pro’s