By Dan Mason

Getting Zone 2 Training Right – The Foundation of Polarised Training

Run Slow to Run Fast

For the last 2 years I have been using low HR training methods to form a solid endurance base for myself and for my athletes – The results have been fantastic, though the initial switch was hard to master. It is never easy changing your running style to accommodate a new training regime and keeping your HR in check on a group ride can be frustrating when you reach the hills. Initially for me my 30 to 60 min runs were almost a minute slower per kilometre than what I was used to, I also had to walk to keep the HR down on the inclines but after around three months I was almost back to my running speed but with a HR of around 15 beats lower – 18 months down the line I am now running as fast as I was previously, if not faster, but can keep the HR down whilst doing so, even on runs of over 2 hours. Over long runs or rides with a constant effort you will see heart rate raise (cardiac drift) the challenge here is to accept it and slow down to keep your heart rate under control, given time this naturally improves through polarised training. Cycling efficiency has also improved, especially on the inclines, it is all about building the engine, refining it and enabling it to be as efficient as possible.

Heart rate training incorporating polarised training methods of 80% relatively easy effort and maximum 20% hard efforts is not followed as much as it should be.  This is due to most athletes wanting to or having the mental need to push too hard on the easier sessions to feel they have benefited form the training. This then leads to the athletes not recovering from the easier sessions and not able to push hard enough on the hard sessions. You can still utilise power meters and pace, but over time if you follow HR method then the power number will go up for the given heart rate rather than heart rate becoming lower for given power as you get fitter meaning the strain on the body is less and the training stagnates rather than improves.

In recent years HRM’s (Heart Rate Monitors) appear to be much more reliable and with the rise in smart watches they have become a daily monitoring system for many more people, with most smart watches having an optical HRM built in. Optical HRM’s are great for monitoring sleep, and daily use but if you want to monitor heart rate in real time whilst running or cycling then a chest HRM is the way to go, these are much more accurate and generally show actual HR rather than jumps in HR that the Optical sensors can. 

The benefits of polarised training or low Heart rate training

Increased endurance, higher fat burning capability, reduced recovery time, limits the risk of injury, increased efficiency, increase aerobic capacity, go faster for longer, fewer GI issues, training to run at your HIM or IM distance pace. Many do not appreciate that the best way to improve VO2 is in fact a lot of Zone 2 work.

You may ask what are the downsides of low HR/zone 2 training? Well, apart from struggle with keeping the HR down there are very few, your max HR may reduce, but this is no bad thing, you still complete hard efforts to compliment the training.

So why not just run or cycle to feel? I have found that a comfortable run speed and even cycle speed was generally in the Zone 3 of a 5 heart rate zone – Zone 3 is neither a high/hard effort or an endurance based effort therefore its somewhere in between, working in this zone doesn’t make huge improvements, but does feel comfortable. A lower heart rate, around zone 2, aids endurance, this increases fat burning capabilities and less reliance on carbs for fuelling, it builds aerobic base capabilities and allows you to be active for longer without “blowing up”. Working the top end of Zone 4 works the body hard and helps to increase speed endurance and improve your lactic threshold, this coupled with Zone 5 work can improve overall speed but should only be done for limited periods.

The 80/20 rule

If you want to improve to be faster or run longer then you need to improve the engine and your heart is where it starts, get the heart working in the right zone and reap the rewards, generally look at working in Zone 2 for at least 80% of the time then leave the hard work in Zone 4/5 for less than 20% – staying away from the comfortable Zone 3 when using a 5 zone HR model for all but race prep sessions if you race is performed at zone 3 (Ironman to 70.3 race prep sessions)

 Keeping the majority of your runs and cycles under 75% max HR or around 85% of your threshold HR, depending on your overall endurance fitness, means you have to slow down on inclines to keep the HR in check. On days where you complete intervals or “efforts” these are generally minimal but are hard efforts above 85% max HR or higher than 95% of threshold for the duration of the interval with recovery back to lower HR – By working the majority of the training at a lower heart the body becomes better at burning fat for fuel as apposed to carbs, this means you can train longer without the necessity to fuel on carbs as much, however when the heart rate is elevated and in race situation the body will still require additional carbohydrates as fuel to maintain this. The ability to utilise Carbs is still important and should be trained within the correct sessions.

And Finally…

Its not all dull efforts though, challenges such as HR hill climbs whether cycling or running, 5k runs, cycle circuits, lowest HR hill climb within a time, 1 mile run test, half marathon HR challenge, marathon HR challenge – my favourite is running as fast as I can on a local route whilst keeping HR in the lower end of zone 2 and monitoring my progress over time.


Hope this helps frame some thoughts on why training aerobically is so important.

Dan Mason.

Triathlon Coach