Zone 2 training currently seems to be one of the big training fads – I’d say it has some parallels with Maffetone training which I have written about extensively.

For the uninitiated zone 2 training is running at between 60-70% of maximum heart-rate. If your maximum heart-rate is 200beats per minute then at the 70% max that means you should run below 140bpm. The problem is as a training strategy this probably won’t work for beginner runners.

There’s a couple of reasons for this. Firstly beginner runners haven’t begun to tune up their physiology yet. Their hearts are relatively still ‘weak’ whereas for a well-tuned athlete their heart has grown in size and is outputting more blood with each beat. That’s why the resting pulse drops with regular exercise. Think of it this way, if your untrained heart is beating 80 times per minute just to supply enough oxygen to the body when you’re at rest; if the heart doubles in size and therefore pumps twice as much oxygenated blood around the system then it now only needs to beat 40 times per minute to meet the body’s needs at rest. NB I use this “doubling in size” for ease of demonstration rather than an accurate representation of what may happen. I can’t find how much a heart will grow with training and it doesn’t really matter; only to understand that with training your heart will get more efficient. And of course that drop in resting pulse will mean that you also experience a drop in pulse when exercising. It gets easier to run with lower values once you’ve pushed the heart in training. Unfortunately with Zone 2 training, you’re not really pushing it that hard so that adaptation isn’t going to happen.

The other problem is that when beginner runners start training and they are holding themselves back to heart-rates which are relatively low they can only do this by  running slowly. The problem is when you’re training slowly, you only need to engage the slow-twitch muscle which is already relatively decent at working aerobically; so again there isn’t much benefit being accrued.

And this is all before we discuss how accurate or inaccurate heart-rate monitors are. While they may be accurate a fair amount of the time; they can also be inaccurate at the start of runs or when you’re near electrical systems. But also your heartrate can vary from day to day depending on the weather and conditions and even just between the start and end of the day. So to then try and train to a specific range can have you  running much slower than you ought.

Successful runners

The truth of zone 2 training is that for it to be useful you need to be doing hours of it each week. Elite 5K/10K/marathon runners are training for the better part of two hours per day, every day of the week. Their training is built on having 2-3 quality sessions sessions per week and then perhaps spending the rest of the week in zone 2 to build some more fitness while recovering before their next quality session.

This is the key thing to understand about training, it’s the quality sessions that get them faster whether that’s a hill session; threshold work, some kind of extended tempo run or whatever. The zone 2 training is beneficial to them as part of a bigger picture but it is not the focus; it just allows them to log more training without getting broken down and injured.

Progressive Overload

Basic sports science says that if you want to improve at any exercise you have to use what is termed “progressive overload”. That’s a fancy term meaning that you keep challenging your body over the course of a training programme. And this is pretty much where Zone 2 Training falls down – for most runners running at a heart-rate below 140bpm isn’t creating any sort of challenge to the body so there is little-to-no stimulus for the body to adapt.

With running you’re typically going to create challenge either by running faster or running further or a combination of both. But if you’re doing easy runs at low heart-rates you’re not going to be running faster; in fact you’re going to be doing the exact opposite – holding yourself back from running too fast. That means the only way you might benefit from zone 2 training is by running further and that’s really what the elite athletes are using it for – they’re challenging their bodies to improve their aerobic system so that it will support the training they are doing at faster paces.

If you’re a beginner runner who only does a couple of hours running per week then perhaps doing Zone 2 training will help you increase the amount of training you do in a week. Perhaps you increase to 6 or more hours and you start to feel much more capable when you run. That’s great but at some stage you’re going to hit a maximum amount of training time which you can allocate to running each week whether that’s because of work, family or other life commitments or because your body is telling you it doesn’t want to do it. Once you reach that limit, then your training week becomes the same week after week and there is no progressive overload challenging the body. You have to introduce some kind of faster work to create that challenge. And the moment you introduce some faster running is the moment when you’re no longer doing Zone 2 training; you’re beginning to add in quality sessions and that is training like any successful runner!

What’s the alternative?

For me the alternative is turning the heart-rate monitor off and building a training schedule where you are able to run for hours per week with progressive overload. I always think of what Arthur Lydiard wrote in “Running to the Top” about how to begin running …

The stranger to jogging or running will follow his medical check by running easily out for, say, five minutes and then turning for home. If he makes it back in the same time, he’s already learnt to move aerobically. If he struggles, he’s gone out too fast. But even if he feels good on the way back, he doesn’t make the mistake of finishing with a sprint. The ideal way to finish is always to feel that you could run some more.

That five minutes out and back routine should occupy a few days to accustom leg and arm and body muscles to the activity. The beginner can then start adding time on his /her feet.

When you can do 15 minutes every day, or at least every other day, step up to 30 minutes, followed by two days at 15 minutes, another 30, another two 15s and so on. Always give your body adequate recovery. The go out to 45minutes, with two 15-minute days in between, and then onto an hour plus two 15s when you can handle it. Then you can start to bring up the intermediate days – alternating an hour, two half hours, an hour and so on.

While this may not sound like progressive overload it works. Notice there’s nothing in there about heart-rate monitors and holding back to a certain number. It’s about letting the body dictate what will work.

I have created base training plans and what I’ve always seen with runners following an easy running schedule is that their heart-rates will be in the 150s 160s, sometimes even in the 170s. And they will tell me it feels easy. Yet those numbers are way above zone 2 and I’m not asking them to hold back. I’m allowing them to build their initial fitness and for their heart to adapt and most importantly to start running quicker.

Eventually there comes a point where it stabilises and they reach a decent pace. Not necessarily world class pace but they haven’t been holding themselves back achieving 7-8min/km or 11-12min/mile wondering why they aren’t seeing any improvement. If aerobic training is working you will see results within 6-8 weeks whether that’s getting faster, seeing lower heart-rates or simply feeling that the runs are getting easier. When you reached that stage you can stick with these runs watching the pace continue to build or start to introduce some quality sessions.