Running wearables and the data they show: what are cadence, heart-rate zones and lactate threshold?

And how can they help you be a better runner?

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The allure of a wearable has them flying off the shelves. Buy one and you can achieve your goals and become a better version of yourself. Who wouldn’t want that? In reality it takes a bit more work on the wearer’s part. We don’t just mean physical exercise and will power, but understanding too.

It’s all good and well knowing how fast you’re running or how many beats per minute your heart is hitting. But to have the knowledge to improve, it can be helpful to delve a bit deeper.

We’re going to explain the big measurement metrics that are popular with running wearable brands now. Be warned, once you know more about your training data, that’ll be one less excuse to not be the best you that you can be.

What are heart rate zones and how do they work?

When your heart rate speeds up that means you’re working harder. Sadly, that’s not all you need to know. There are various zones that your heart rate falls into between resting and maximum. Maintaining intensity within specific zones when you run (or do any exercise) can help you hit specific fitness goals.

For example if you’re hoping to burn fat in your training, it’s actually better not to work too hard. By keeping your heart rate lower in what is generally known as the 'fat burning' zone, at about 60-70 percent of max HR, your body better metabolises fat for energy. 

So brisk walking, light jogging and the likes of yoga, which elevate your heart rate, but not too high, are great for fat burning.

• The next step up is the lower aerobic zone, at 70-80 percent of max HR. This is ideal when building muscle. 

• The upper aerobic/threshold zone sees you training at 80-90 percent max HR. This is good for improving your body’s ability to flush out lactic acid, making your threshold higher. Put more simply, it's ideal for those looking to run longer distances. 

• The top zone (90-100 percent of max HR) is specifically for fast twitch muscle fibres and works for increasing speed over short distances – so one for sprinters and middle-distance runners working on their sprint finish.

The big issue with cardio zone training – just check out any running forum discussion about it – is how do you calculate your maximum HR? All the zones stem from that, after all. 

The 'classic' method is to deduct your age from 220. If you're about 40, you can immediately tell this is bollocks, by observing the wildly varying fitness levels of other people you know who are your age.

A more accurate formula is to include your average resting heart-rate in the calculation, which is what Garmin's best running watches do. The most accurate way is to have it tested under medical supervision, but that's beyond the scope of even the most advanced wearable.

One final note on this: if your heart-rate is regularly going up above your maximum HR by more than 1 or bpm, clearly it is not your maximum HR, so you may need to recalculate your zones. And although 'maximum HR' sounds very final, if you do go above it, although it's not advisable to do so, your heart will not immediately explode.

What is cadence and how can it help you?

Cadence is a measurement that applies to both running and cycling training and can help improve your performance. In the case of running it’s the number of steps you take in a minute (for cycling it’s the number of revolutions of the crank via the pedals per minute).

Why should you care about cadence though? Because this measurement allows you to use your energy more efficiently. If you’re hitting the ideal cadence that essentially means you’re going at the fastest speed for the amount of energy you’re putting in. 

When running, shorter steps mean more per minute and also mean your weight is better distributed to help carry you forward. That's as opposed to longer, more lunging steps that strain your balance muscles and waste energy. And giant steps, which are what you take, walking on the moon.

The inexpensive Moov Now is a good gateway drug for 'getting into cadence'. It uses (slightly robotic, but you get used to it) voice coaching in association with a sensor on your ankle, helping you run at different cadences until you find your optimum. It also gives all manner of other running insights. It can help with HIIT workouts, swimming, cycling and more too, but it's primarily a runner's tool.

Incidentally, for cycling, hitting the ideal number of revolutions per minute means you’re not using too much force, from slow, powerful movements, or too much energy, from superfast spinning. Average cyclists have a cadence of about 60 while the pros are nearer to 120. You probably want to hit somewhere in between at about 90-100 for the ideal energy output.

What is lactate threshold and how can it help?

Well, for a start lactate doesn't help you so much as hinder you. Lactic acid is the chemical released by the muscles when they’re working without enough oxygen. While that’s great to keep you going even when tired, it is also the reason your muscles hurt the next day after you train too hard and cause lactic acid release.

So, by knowing exactly when you muscles run out of oxygen and start releasing lactic acid – the 'lactate threshold' – you can ease back and avoid overtraining, allowing you to get back out there the next day without quite so much hobbling.

This is a very tough metric to measure accurately without invasive surgery. However Garmin's Forerunner 935 does include a lactate threshold test that can determine the level you should ideally stay below while working out. It seems unlikely this is 100% accurate, but it can still help you avoid overtraining, by erring on the side of caution.