How to use Training Zones the Right Way (Part 1)

Training zones, lactate threshold, anaerobic threshold, VO2 max: training buzzwords. Do you know what they mean? Do you know how to use them to improve your training? Find out in this three-part series. (Part 2, Part 3)

Part 1: Training Zones based on Lactate Threshold

Does your watch tell you what training zone you’re in? Do you have any idea what it means? Today, we will break down the useful (but oft misunderstood) concepts of training zones.

Firstly, be aware that there are different ways to summarize different training levels. Many fitness watches divide training into numbered or color-coded levels, from warm up pace to sprinting. If your watch tells you you’re in Zone 3 and your coach wants today’s workout to be Level 1, don’t freak out. They might just be different names for the same thing. I use a nomenclature that sets easy and distance pace at Level 1 (L1,) anaerobic exertion at L5, and everything else somewhere from L2 to L4. Much the same as measuring temperature by fahrenheit and celcius, different systems all refer to the same training metrics, they just use different names and numbers.

Any good delineation of training zones will be based around a few key markers. Fitness watches tend to base their training zone approximations on their estimate of your max heart rate. I prefer to base training levels around lactate threshold: an important tipping point in an endurance athlete’s training.

If you’re going to understand only one piece of training jargon, lactate threshold is a good one to grasp.

So what is it? Let’s break it down:

1) Say you go for a distance run, starting out at a comfortable pace. You’re out there burning mainly fat for fuel (whether you know it or not,) and producing a small amount of lactic acid (about the same amount as at rest), which gets carried away from muscles in the bloodstream as lactate. The conversion of lactic acid to lactate leaves behind a few hydrogen ions.

2) Then you pick up your pace. You’re breathing harder, and (unbeknownst to you) burning some sugar (glycogen) along with your supply of fat. You’re also producing more lactic acid, sending more lactate away in the bloodstream. It becomes harder for your bloodstream to keep up. You’re accumulating hydrogen ions in your muscles, which makes the muscles begin to get that burning sensation.

Now you’ve transitioned to burning glycogen as your primary fuel instead of fat. If you could graph* your blood lactate over the course of this scenario, it would look something like this.

Lactate Threshold Curve

Beyond the second inflection point, lactate production increases at a constant rate (the curve becomes a line.) This inflection point, roughly speaking, is lactate threshold.

It’s a very functional metric to base training around. Imagine if you could produce less lactic acid (and muscle-burning hydrogen ions) at any given pace. Or imagine you could clear lactate away a little better, or tolerate the hydrogen byproduct better.

You could go faster for longer, before crossing the threshold. And going faster for longer is usually the goal of endurance athletes.

So we do some training at or near lactate threshold, or at least, we should.

Next week (Part 2): training at lactate threshold. We will review the importance of proper training pacing, common errors, and how to do it right, including a DIY test to find your lactate threshold.

*You can have this scenario graphed by having testing done on a treadmill in a lab

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