Zone 3 Running: Key training zone or waste of time?

Today, I’m going to answer whether Zone 3 is a crucial training zone or whether it’s a waste of time.

Zone 3 running refers to a specific level of intensity that falls between easy runs and hard threshold workouts. It’s not easy, but it’s not hard, so it’s often known as steady running.

Some running coaches argue that Zone 3 training is key to performing well at longer events like the half marathon and marathon, while others make it out to be some evil thing that should be avoided at all costs.

Who’s right?

Both. Here’s why:

• Zone 3 is the zone in which you typically run most of a marathon.
• It develops both your aerobic and glycolytic energy systems.
• But, if you spend too much time in zone 3, you risk overtraining.

Let’s dive in.

Understanding Zone 3

Training zones refer to different intensity levels during cardiovascular exercise that target specific physiological adaptations. These zones are typically determined by heart rate, as it provides a reliable indicator of effort and intensity.

You can work out your Zone 3 heart rate range using this free calculator if you don’t already know what it is.

Training zones play a crucial role in optimising running performance. You can target different energy systems and develop specific physiological adaptations by training at different intensities. Each training zone has unique benefits and improves overall fitness and performance.

Zone 3 is a strange one. It’s a bit of an in-between zone — you get some of the benefits of Zone 2 in building your aerobic system, and you also get some of the benefits of Zone 4 (threshold training) in that it also works your glycolytic/lactate system.

Some coaches talk about Zone 3 as the “sweet spot,” as it gives you the best of both worlds. Others call it the “grey zone,” as it maximally works neither your aerobic nor glycolytic/lactate systems.

Let’s dive into the benefits and drawbacks.

Benefits of Zone 3 Running

Zone 3 training can provide a lot of benefits in the right context:

1. It’s great for marathons: Most people will run the majority of a marathon and a good chunk of a half marathon in Zone 3. If you’re training for either event, it’s a good idea to run in Zone 3 once per week, either as part of your long run or as a dedicated midweek run.
2. Improved aerobic capacity: Like Zone 2 training, Zone 3 training will stimulate your aerobic system to a high degree, increasing your body’s ability to deliver oxygen to the working muscles and making it more efficient at producing energy. This all happens as a result of increased capillary density, mitochondrial density and function, and cardiovascular strength.
3. Increased lactate threshold: Zone 3 running calls upon your glycolytic/lactate system, so it can help increase your lactate threshold and become more efficient at using carbs as fuel. It’s not as effective at doing so as Zone 4 training, but by training in Zone 3, you can improve your body’s ability to tolerate and clear lactate, delaying the onset of fatigue.
4. Enhanced endurance: Steady runs in zone 3 challenge your body to sustain a higher pace for longer durations. This trains your muscles and cardiovascular system to better withstand fatigue, leading to improved endurance.
5. Injury rehab: Because it’s an in-between zone, it can be great during injury rehab. It’s a good way of adding a little bit of pace into your training without going full-on into threshold and interval workouts.

Drawbacks of Zone 3 Running

There are three main downsides to Zone 3 running.

1. Risk of overtraining: Training too frequently in zone 3 can increase the risk of overtraining. Zone 3 training is not easy, so it places a higher recovery demand on your body than Zone 2 runs. Generally, you don’t want to do more than two runs in Zone 3 or above most weeks.
2. Limited specificity: Zone 3 training may not be fast enough to train for distances like the 5km or 10km, optimally, and it might not be slow enough to train or slow enough for ultras optimally either. Different races and events require different energy systems and intensities. Zone 3 training is great for marathons and half marathons (for most people), but you’re better off focusing on the other zones if you’re training for other races.
3. Plateau effect: If zone 3 running becomes the sole focus of your training, you may experience a plateau. You’re not stimulating your aerobic, glycolytic or anaerobic energy systems maximally, and you may find it hard to increase your weekly volume as the training load per session is high. Zone 3 training works well in a balanced training plan, but it doesn’t work well if you do it all the time.

Why does it get such a bad rap?

I don’t think Zone 3 is a grey zone at all. It has it’s place.

The main reason it’s viewed so negatively is that beginner and intermediate runners often spend most of their easy runs running in Zone 3 instead of Zone 2.

I’ve been there. It’s easy to do, especially when you’re starting out. You feel like you have to run ridiculously slowly to stay in Zone 2, and it can feel embarrassing. It’s so tempting to speed up a little bit in an effort not to be constantly overtaken by other runners. But those runners are probably making the same mistake — running in Zone 3 instead of Zone 2.

Over time, lots of Zone 3 training will place significant recovery demands and impact forces on your body, which can result in overtraining and overuse injury. If you’re suffering with things like shin splints or runner’s knee, it’s worth evaluating whether it’s because you’re running your easy runs too fast and in Zone 3.

In short, there’s nothing inherently wrong with Zone 3 training, if that’s what the plan says, but going for an easy run and ending up in Zone 3 is one of the most common and costly mistakes you can make as a runner.

If you are looking for more advice on running in Zone 2, these two posts on my blog could be useful:

• Why Can’t I Stay In Zone 2 When Running?
• The Ultimate Guide: Building Your Aerobic Base For Running

Incorporating Zone 3 running into your training plan

If you think Zone 3 training is right for you, let’s explore how to incorporate it into your training plan. Here are some tips:

1. Gradual progression: If you’re new to zone 3 running, start by incorporating shorter tempo runs at this intensity and gradually increase the duration and frequency over time. This allows your body to adapt and reduces the risk of overtraining.
2. Mix it up: While zone 3 running can be beneficial, it’s essential to include a variety of training zones and types of workouts in your training plan. Don’t train in Zone 3 more than once per week. Incorporate easy runs, long runs, interval sessions, and strength training to develop a well-rounded fitness base.
3. Judge your effort using heart rate or pace: Heart rate monitors can be valuable tools for tracking your effort level during zone 3 runs. Otherwise, you can judge your effort by pace. A good rule of thumb is 10–20 seconds slower than your marathon pace.
4. Listen to your body: Training zones are helpful guidelines, but it’s essential to listen to your body and adjust the intensity based on how you feel. Some days, you may feel stronger and able to push harder, while others, you may need to dial back the intensity to allow for proper recovery.

Here’s an example from my last marathon training programme to show how you can fit Zone 3 runs into your training plan:

• Monday: Zone 2 run
• Tuesday: Interval or threshold run (Zone 4/5)
• Wednesday: Zone 2 run
• Thursday: Zone 2 run
• Friday: Strength training
• Saturday: Zone 3 long run (e.g. 5km warm up, 15km in Zone 3, 5km cooldown)
• Sunday: Rest

My Take

Zone 3 running is neither a “sweet spot” nor a “grey zone”.

It definitely has a place in:

• Marathon training
• Half marathon training
• Injury rehab

But unless you’re in any of those boats, you’re better off spending more time in Zones 2, 4, and 5.

You will build a stronger aerobic base using Zone 2 running rather than Zone 3, as Zone 2 running works you’re aerobic system maximally and is easy to recover from. Equally, you will increase your lactate threshold and improve your 5/10km times more by spending your 1–2 hard runs each week in Zone 4 and 5.

Key Takeaways

• Zone 3 runs are performed at a moderate intensity, and it’s often the zone most runners spend the majority of a marathon in.
• In Zone 3, the aerobic and glycolytic systems are both used, but neither are working maximally.
• Zone 3 training is great if you’re training for a marathon or half marathon, but there are better ways to train if you’re looking to improve your 5/10km.
• If you train in Zone 3 too much (or accidentally), it can cause you to plateau, overtrain or pick up injuries.