The Magic of Zone 2

Many of you might hear that running in Zone 2 is essential for running a good 10K, Half Marathon or Marathon. But why is that and how do you know that you are running in Zone 2. In order to understand this, you need to understand running zones. In fact, there are many different zone structures, but generally in coaching we speak about Zone 1 to Zone 5. They are related to heart rate zone but only because the harder you run, the higher your heart rate. It is better to relate them to intensity. Besides the fact that heart rates can vary because of stress, temperature, hormonal cycles, etc, not many have done the correct physiological testing to measure maximum heart rate or are using the optical heart rate sensors at the back of the watch to measure heart rate, which are prone to measuring incorrectly.

Let’s break down these zones – Zone 1 is basically the lowest intensity – like walking, doing house chores or gardening. It might raise your heart rate slightly but it doesn’t feel like a real workout. Right above that is Zone 2. This is where you do something that is a little bit more intense (like a very easy run) where you can have longer conversations with someone without getting too much out of breath. Some coaches will see Zone 1 and Zone 2 as one zone (specifically if they use a three- zone approach). Zone 3 is your 10K, half marathon and marathon zone, where you raise your intensity to a level where you might be able to talk in short sentences but it feels much harder to have a full conversation. You can still sustain this intensity for a full race. Zone 4 is what coaches call the Threshold Zone, this is the zone where you run at an intensity that doesn’t really allow you talk – your breathing gets quite heavy and your legs fatigue easily (as lactate builds up and cannot be recycled). This might be the zone for a shorter run, like 800m reps on track or your fastest park run. Zone 5 is basically full out sprints; you might sustain this for a minute but not much longer.

In order to understand the importance of Zone 2 – you need to understand where your energy comes from when you are working out. All our cells contain mitochondria. In these mitochondria a process takes place where, in simple terms, our fuel (food) and oxygen react to create energy (almost like a car engine). In Zone 2 we make our cells create more mitochondria, so we increase the number of engines we have, and obviously the more engines we have – the longer we can sustain a level of intensity. However, in the Zones above – we increase the density of the mitochondria, so we make them more effective in using the fuel (and oxygen). In order to build a ‘big’ aerobic running base it is therefore important to run in Zone 1 and 2. If you want to become quicker, you need to add Zone 3, 4 and 5 runs (but as they are much more intense, you should only do around 20% of your running in those zones .