If you’ve ever worked with a running coach, you’ve probably heard them talk about Zone 2 training. It’s a popular topic amongst endurance athletes. Opinions vary on whether it’s best to do primarily low heart rate training (easy runs) or a more aggressive mix of threshold and tempo runs.
Zone 2 training involves exercising at a low-intensity level where the body primarily relies on oxygen and fat to produce ATP (adenosine triphosphate) as fuel. Spending more time in this zone can help improve athletic endurance, increase the volume and efficiency of mitochondria, and improve cardiovascular health. In short: it’s a great way to build stamina and improve your personal bests!
Here we’ll look at exactly what Zone 2 Training is and why it’s important for base-building and endurance.
Let’s get right to it!
Understanding Training Zones
Getting a grasp of what Zone 2 training is involves first understanding how our bodies convert the food we eat into fuel to power our existence.
Every cell in the human body draws fuel from adenosine triphosphate – ATP for short. Walking, running, deadlifting, and even reading are all functions that ATP powers. This fuel is produced in three distinct ways:
- Oxidation – This is the process that produces the majority of the ATP used by the body during the day. When we breathe, oxidation converts fatty acids to ATP. It’s an essential process when it comes to Zone 2 training.
- Glycolysis – When performing more intensive exercises, such as weight lifting and sprinting, your body temporarily stops oxidizing your fatty cells instead of burning carbs/glycogen to refill ATP stores. This process is called glycolysis and produces a large amount of ATP, though less than oxidation.
- Recycling stored ATP – When ATP provides cells with energy, it sheds a phosphate to become adenosine diphosphate (ADP). Then, creatine in the body provides the ADP with phosphate to make up for the lost one, turning the ADP into ATP once more. This ‘recycled’ ATP can then be used as an energy source for the body.
One thing to note is that ATP can also be derived from lactate. To summarize, the body can convert lactate to glucose, which is then used in the process of glycolysis. It’s an incredibly technical process that we won’t delve into here, but it is endlessly fascinating.
Where Do Training Zones Fit In?
Physicians and exercise scientists have researched and developed ‘training zones’ over the years to help coaches and athletes understand the muscle fibers and energy systems used during certain exercise intensity levels.
One of these systems separates intensity training into six Training Zones. On one end of the spectrum is Zone 1, the least intensive zone. It covers activities like sitting, walking, and very low-effort processes. Zone 6 lies on the other end of the spectrum and requires the most effort. This zone involves deadlifting a heavy sit, sprinting as fast as possible, and other effort-intensive exercises.
Here’s a breakdown of the primary energy sources used for each Training Zone:
- Zone 1 – Fat
- Zone 2 and 3 – Fat, some carbohydrates
- Zone 4 and 5 – Carbohydrates
- Zone 6 – Carbohydrates, some creatine phosphate
The fuel type used by your body to synthesize ATP differs as you increase the intensity of your exercises. In the first two zones, fat is your primary source. As you move into Zone 3, you’ll begin using more carbs, and when you approach Zone 6, your body will begin using creatine to form ATP.
Exercising in Zone 2
When operating in Zone 2, the intensity of your exercise is enough to stimulate the mitochondrial functions of your cells the most. You’ll be able to meet your body’s demand for ATP using oxygen in its mitochondria and fat alone. If you increase your exercise intensity, your body will begin drawing on more carbohydrates to make ATP via glycolysis.
Zone 2 Cardio – Why It’s Good for You
Why does performing Zone 2 training benefit your exercise and endurance results? Here are some of the reasons:
Improves Your Athletic Endurance
Whether you’re a cyclist, a dancer, or a runner, keeping yourself in Zone 2 for longer will help you move faster for more time. Cardio work in this zone is often used by elite athletes for decades and is one of the key aspects separating amateurs from professional runners.
Pros take it slow, though it won’t feel that way at first. Something counterintuitive when it comes to spending time in Zone 2 while running or cycling is that, while it may not feel as though you’re pushing your limits, you will become a better athlete for it.
It’s true what they say: running slow is a great way to eventually run faster.
Over time, you can go longer and faster while maintaining a low heart rate. As you continually train your body to utilize fat as fuel, you’ll increase your speed without burning carbohydrates. What’s more, using fat allows you to train for longer since you have an almost unlimited fat supply.
Increases Mitochondria Volume and Efficiency
At Zone 2, you’re stimulating your mitochondria to create ATP the most. As you spend more time in this zone, your body will react by creating more mitochondria to power this activity. The more mitochondria in the body, the more your body will be able to oxidize fat and convert it to fuel.
What’s more, Zone 2 also improves the efficiency of your mitochondria. The more time you exercise in this zone, the better your body becomes at converting fat into energy. The body’s inefficiency at converting fat to fuel can lead to several health issues, like dementia or insulin resistance.
Improves Your Cardiovascular Health
Perhaps the most important benefit of Zone 2 training is that it improves the efficiency of your heart, thus improving your circulatory system. Your heart becomes stronger, eventually requiring fewer beats to move blood throughout the body.
Over time, your body will expand the vascular system, allowing it to circulate oxygen-rich blood more efficiently. The result is an overall benefit to your cardiovascular health, which, in turn, results in better exercise performance.
You’ll notice a decreased resting heart rate as well. The average resting rate for adults is 60 bpm – 100 bpm, but with Zone 2 training, it can often average between 50 bpm – 70 bpm.
If you’re wondering why your heart rate is high on a slow run, it could be a sign that more Zone 2 training is required. And that’s when you might want to consider a training plan that focuses on low heart rate training, like the MAF Method.
Reduces Your Risk of Injury
The great thing about Zone 2 is that it puts very little stress on the body, allowing you to increase the volume of your training regimen without fatigue or injuries getting in the way. Even after a long Zone 2 cardiovascular session, you should be ready for one again the day after if you’ve done it properly.
What’s more, it aids in recovery. When you’re exercising in this zone, your blood gets pumping, providing your muscles with nutrients to help them recover after a session of weight lifting.
The Potential Downsides of Zone 2 Workouts
When dosed appropriately for a trained runner, Zone 2 training is highly beneficial. But you mustn’t do all of your training exclusively in Zone 2.
If you are only spending time in Zone 1 and 2 for extended periods, you’ll eventually plateau in your progress, or worse – you’ll get slower. Lower intensity zones leave out the neuromuscular system. Power is not increased with biomechanical mechanisms, muscle fibers are not activated, and you’ll never improve your lactate clearance.
Spending around 20 – 30% of our training time in higher-intensity zones is important. Interval workouts, moderate running, and hill sprints are all valuable in training for adding extra speed and running faster.
Don’t Train for Metrics
Training for metrics can also cause plateaus in your performance. It’s essential to know each run’s purpose and focus on that purpose.
For instance, if you are training to compete in a hilly marathon, pushing your heart rate into Zone 3 on uphills can greatly benefit you. While walking up hills will keep you in Zone 2, it won’t be beneficial to the demands of the race day.
Running up those hills in Zone 3 will help you practice the biomechanics you’ll use for running up hills on the day of your race. Walking uphill doesn’t take into account the importance of training your biomechanical patterns and muscle fibers.
Is Zone 2 Good for Beginner Runners?
If you’re a beginner, you might struggle to keep your heart rate in Zone 2. Your stroke volume has not yet adapted to the demands, and your heart rate is naturally higher at this stage. The main factor here is that you don’t yet have the cardiac training required to run at a low heart rate.
Of course, as you become fitter and a better runner, your stroke volume will increase, allowing you to run with lower heart rates. This doesn’t mean you should run as hard as you can every time – moderate intensity can benefit you as a novice athlete.
Spending around half of your training time at a moderate intensity can be beneficial, especially if you’re new to the sport or do not run at high volumes. Spending a good chunk of time in Zone 3 offers stimulating aerobic exercise, helping you improve your running biomechanics.
Once you’ve been training for a while and have developed your cardiovascular system (which usually takes around six months), you’ll be able to focus on slowing down and improving your performance via Zone 2 training.
Wrapping Up
To sum it all up, Zone 2 training is absolutely important to improving your running performance and cardiovascular efficiency. However, it’s essential that you don’t spend all of your time in this zone and that you break into higher intensities to stimulate your neuromuscular system.
If there’s one key takeaway we want to leave you with, it’s this: don’t train for metrics. Train for performance. Happy running!
