Zone 2 Training: The Art of Slowing Down

Disclaimer: I'm an amateur athelete who started training seriously this year. Please do not take this as expert advice or scientific advice for zone 2 training. Everything mentioned in this article has been derived from various articles online or videos based on my research. Please do your own research or consult an expert before engaging in any training program.

As mentioned in my 2022 planning, one goal I have for this year is to complete a half marathon ideally under 2 hours 15 minutes. Contrary to cycling, running was quite new to me and it was challenging in the beginning. At the time of writing this post, I can easily run a 10K distance and have completed a sub 30min 5k run. Even though I enjoy running, I use to feel quite exhausted and tired at the end of my runs. I was looking at ways to train efficiently for long-distance running without exerting my body too much and stumbled upon the concept called Zone 2 Training while reading Finding Ultra by Rich Roll.

In a nutshell, zone 2 training involves training at a low-intensity level for a longer period of time. The goal of zone 2 training is to sustain an intensity for longer periods of time such that heart rate lies in the range of 60-70% of the maximum heart rate value. Training at this intensity is incredibly easy and boring at the same time. When I started zone 2 training, I was a bit sceptical as it seemed too easy and I always had the attitude of ‘go hard or go home’ when it comes to training. Over time I realized this art of slowing down and how it can contribute to my aerobic fitness. In fact, the majority of high-performance endurance athletes follow the zone 2 training regime and it has proven benefits as per many scientific studies. The concept can be quite tricky to grasp as it’s hard to comprehend how training slow can help us to go faster. To understand it more, it is necessary to understand some science behind zone training and I’ve tried my best to summarise it in a concise fashion.

Science of Zone 2 Training

How an athlete performs depends upon his/her ability to convert chemical energy into mechanical energy. All cells in our body are fueled by something called Adenosine Triphosphate or ATP. Mitochondria in our cells generate ATP mainly in two ways – through aerobic or anaerobic mechanisms. The aerobic mechanism involves the conversion of fat into ATP whereas in the anaerobic mechanism carbohydrates are used. Also in our muscles, we have slow-twitch(Type 1) and fast-twitch muscles(Type 2). Type 1 muscles have a lot of mitochondria and prefer fat as fuel whereas Type 2 muscle fibres are glycolytic and prefer carbohydrates as fuel. Burning glucose or carbohydrates produces lactate and hydrogen ions, resulting in muscle fatigue.

By training in Zone 2, we are mainly using Type 1 muscle fibres and making use of the fat deposits as a source of fuel. The lactate build-up will be limited at this zone and we can maintain our efforts for longer periods of time at this level. Training at this zone stimulates Type 1 muscle fibres, stimulating mitochondrial growth and improving our function to utilize fat in our body. We can preserve the glycogen in our body to utilize in the last courses of the race when we tend to run or move faster. As discussed earlier, utilizing Type 2 muscle fibres will result in the production of lactate. A transporter called MCT-4 present in Type 1 muscle fibres can transport this lactate to mitochondria for the generation of ATP. Thus Type 1 muscle fibres play a major role in lactate clearance as well.

To summarize, training in zone 2 will stimulate Type 1 muscle fibres, which will increase the mitochondrial density in our muscles. This in turn improves fat utilization and increases the lactate clearance in our muscle fibres, thereby increasing athletic performance.

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How to Train

Ideally, 80% of all training should be done in Zone 2 to improve endurance. The most common and easy way to train in Zone 2 is to monitor your heart rate. For this, you need some sort of heart rate monitoring device. I personally use Amazfit T-Rex Pro as it is the only heart rate monitor I have access to. It is a good and affordable option and the results are 98% the same as that of an Apple Watch Series 7 based on my test. If you have the budget, I would definitely recommend you invest in a good heart-rate chest strap or a better watch like Garmin Forerunner. Chest straps usually give more accurate results compared to wrist-based heart rate monitoring in smartwatches.

The first step is to determine your maximum heart rate. I personally use the maximum heart rate from the data of all workouts I have done. You can also involve in an activity like cycling or running such that you increase your pace every 2 minutes until you can sustain it. Your heart rate at this point will be your maximum heart rate. Or, you can use the traditional way of finding heart rate by subtracting your age from 220. (If your age is 25, the max heart rate will be 195 bpm).

Once you have a value for your maximum heart rate, a ballpark estimate of your zone 2 heart range will be 70-80% of your heart rate. So if your maximum heart rate is 195bpm, your zone 2 range will be 136-156bpm. There are a number of calculators available online that you can use to calculate your zone 2 range. I have seen many people recommending the MAF 180 Formula, which you can use to calculate your upper zone of zone 2.

Training in Zone 2 is simple yet hard at the same time. You can run, cycle or do any activity such that your heart rate falls between the range of your zone 2 heart rate levels. Say if you’re running and your heart rate goes above your upper limit, slow down or start walking to bring down your heart rate. This is quite hard as we all have this tendency to go hard and running slow when you start training at zone 2 is quite painful. My personal suggestion would be to start training in zone 2 by cycling as it is much easier to maintain zone 2 levels during cycling than compared to running. If your smartwatch allows, try to set up alerts on your smartwatch such that it alerts you when you fall out of the range. Ideally, 80% of all your training should be done in Zone 2.

My Experience so far

I do not have any miraculous experiences to share when it comes to zone 2 training as it’s been only a few months since I learnt about this training method and started doing it. I try to do 4 workouts a week in zone 2 and there are some changes I can notice. I feel very less fatigue and tiredness post workouts these days. After a few times of zone 2 training, every time I run I feel like I could go on forever. In fact, the first 10k I did was by accident. I initially planned to do a 5k run while maintaining my heart rate in zone 2 and once I completed I felt like I could go on forever. So I continued running and completed my first 10k run by surprise. I still struggle to train at Zone 2 as my heart rate keeps on crossing the range at times. When I started I couldn’t even keep my heart rate in zone 2 more than 30% of the time. As I’m writing today, I can easily keep my heart rate in zone 2 80% of the time during most workouts. I’m trying to improve day by day and will update this post once I see some tangible results.

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References
1. https://www.howardluksmd.com/zone-2-hr-training-live-longer-less-injury/
2. https://www.trainingpeaks.com/blog/zone-2-training-for-endurance-athletes/
3. https://www.artofmanliness.com/health-fitness/fitness/zone-2-training/