You may have heard of the 80-20 rule, that 80% of your time spent running should be easy and the rest in harder zones. Here we unpack whether that really is relevant for everyone and put Zone 2 heart rate training into its proper context.
These days, runners are flooded with data that, not long ago, was only available in a lab. I started out with a basic Ironman watch that showed little more than elapsed time. Then came a bulky first edition Garmin that added distance and pace. Now I run with a Coros Vertix 2S, which can navigate routes, track oxygen levels, take ECG readings, and even tell me when to have dinner (well almost!).
Among all this information, heart rate is something many runners glance at but few fully understand. We’ve all heard of zone 1 and zone 2 training, but what do they actually mean, and should we be paying more attention?
What are Heart Rate Zones?
In short, the answer is both yes and no. Let’s start with the “yes.” Heart rate training is now far more accurate, thanks to improved chest and arm monitors that enhance even the data from modern watches. It builds on running by feel or pace—both of which have limitations. Effort can be influenced by emotions, while pace doesn’t account for terrain, weather, altitude, or elevation. Heart rate helps bring these factors together, provided the data is tailored to the individual.
That said, heart rate itself is influenced by many variables, including age, sex, fitness, genetics, temperature, hydration, and even time of day. There’s also a natural delay between changes in effort and changes in heart rate. To make sense of it all, heart rate is typically divided into zones, usually based on a percentage of your maximum heart rate. A quick search of HR zone training will show how these zones are commonly defined.
The problem with focussing on HR Zones
Here’s the first issue: not all training zones are defined the same across platforms.
It then gets even more complicated when you consider that simple percentage-based zones may not be the most accurate method. Instead, many recommend using the Karvonen formula, which factors in resting heart rate:
([Maximum heart rate – resting heart rate] × % intensity) + resting heart rate = training zone
Now we’ve got both heart rate zones and training zones—and all of it hinges on one or two key numbers: your maximum heart rate and your resting heart rate. So how do you find them?
A rough estimate for max heart rate is 220 minus your age, but this is very basic and ignores most individual factors. A more practical method is a 5km time trial, pushing all-out in the final minutes and noting your peak heart rate. The most accurate option, though, is lab testing—well worth considering if you’re serious about training by heart rate, if you truly push to your limit.
The reasons for focusing on HR Zones
So why train by heart rate at all? At its simplest, it reinforces the idea of running your hard sessions hard and your easy sessions easy. Many runners drift into the “comfortably hard” middle ground—often zone 3—where runs feel productive but don’t deliver the full benefits of either true easy or hard efforts. It’s also an easy habit to fall into: the same familiar 45–60 minute loop, no planning required.
You’ve probably also heard of the 80/20 rule: around 80% of your running should be easy, with 20% at higher intensity. Research suggests this applies to either end of the spectrum of runners – elite and beginners, but less applicable in the middle ground. Easy running builds aerobic efficiency and endurance, works our slow twitch fibres, and help strengthen all of our ligaments and tendons without causing excessive stress, and allows you to recover well enough to perform quality hard sessions. It’s also mentally easier—if most runs feel manageable, you’re more likely to stay consistent.
There is a higher success rate for completion of any training plan, if we are more motivated to start each session due to our belief of how easy we will find it. From an anecdotal perspective I think the issue comes with how few people enjoy the concept of running uncomfortably hard. It is something we did as children perhaps when having to compete at sports day, but as an adult is much rarer. Park run to some extent offers a reason to engage in that 20%, but so often the social driver of: running with friends/it’s not a competition/insert your reason <here>, is a bit of an excuse not to push.
Why the fascination with Zone 2?
Zone 2 and the 80/20 became a fascination in sport because there is a section of runners that would have read the above and thought, no – it’s way easier to train hard, and they hate running slower than their natural pace. They are the pros, the super competitive and often new to running. The message of increasing their training at an easy pace was a new message for them, and counterintuitive. For the rest of us, well it’s just a relief!
What’s the takeaway?
Simplify: Rather than getting too caught up in exact heart rate numbers, I recommend of using three effort levels: easy, moderate, and hard. Most runners can judge this intuitively without constantly checking a watch, even if you reference your HR initially to work them out. If you are a beginner focus more on effort than HR.
Zone 2 is the start: Think of HR Zone 2 (easy effort) training as the baseline foundation to your running, without it you will be frequently injured and have erratic training. However, without those punchy hard efforts you are not going to progress further in your training, but that might be ok!
Be consistent: Ultimately, unless running is your paid job, and for most it’s not, enjoyment matters most. Whilst it would be ideal to include intervals, tempos, and speedwork during your training, it’s better to three runs a week in HR Zone 2 than to not run at all. Be consistent and enjoy your running.
Conclusion
Stay consistent, keep it enjoyable, and let that guide your progress, and every so often don’t forget to put your foot down and dip into that uncomfortable 20%!
Written by Run the Wild Running Coach and Head Guide – Karin Voller
