Understand your running watch data – VO2 Max, cadence and EPOC explained

If you're using your running watch just to track your distance and pace, you're missing out on a huge opportunity to improve your running.

Sports watches are packed with sensors and stats that can turn you into a better, faster and less injury-prone runner – it's just a case of understanding the data and using it to your benefit. But knowing how to interpret all that data can be tricky.

If you've picked up a new Garmin watch like the Forerunner 945, Fenix 6, invested in the insanely detailed Polar Vantage V or even gone for a run-friendly smartwatch like the Apple Watch, you'll probably have noticed that there's a whole flood of shiny new running metrics to wade through.

Here are ten running watch stats and what they mean for your PB.

Cadence

Cadence or foot strike rate is the number of steps per minute (SPM) you take. It's a vital stat for assessing the efficiency of your running form and thankfully is something that's relatively easy to improve once you're aware of it.

Just like vertical oscillation, some running watches offer cadence readings from the wrist or will use sensors in a heart rate chest strap to fire a SPM figure to your wrist. Older generations tend to pair up with a shoe pod too.

A typical cadence is between 150 - 200 steps per minute, but experts put 170+ SPM as the sweet spot for optimum running efficiency for reasons best left to the physicists to explain.

A great way to work on your cadence is to find a 170BPM soundtrack for a shorter run and use the beats to quicken your strike rate.

For newer Garmin and Polar watches, you'll also notice a Metronome feature that will play tones at a steady rhythm to help improve your cadence.

If you yearn for the most reliable cadence data, you'll want one of the devices we've recommended below to make that happen.

Find it on: Garmin Forerunner 245, Polar Ignite, Apple Watch Series 5, Suunto 5

Vertical oscillation

Watch any professional runner in action and you'll notice that there's very little movement in their upper body.

Their top half glides swan-like while their legs do all the work under the surface. One measure of this optimum running efficiency is called vertical oscillation and shows the degree of 'bounce' in your running motion.

This bounce is measured in centimetres from a fixed point on your body (in the case of GPS running watches this tends to be a sensor built into the heart rate chest-strap.

Typical oscillation is between 6 and 13 cm with the Paula Radcliffe's of this world moving at the lower end of that scale. So why is it useful to be able to monitor vertical oscillation?

Well, it's all to do with running efficiency and not wasting energy as you put in the miles. Ideally, you'll want to reduce that 'bounce' and that's closely linked to increasing cadence, which we'll talk about next.

Find it on: Garmin Forerunner 945 with Garmin's Running Dynamics Pod, Polar Vantage V with Stryd

Running power

This is the next big trendy running metric that we think you will start hearing more about over the coming years.

Watches like the Polar Vantage V and Garmin's newest top end Forerunner watches already offer support for running power, which is designed to offer a way another way of better managing your running performance over training session and a race.

What is running power? We have a comprehensive guide on running power, but essentially power is work rate and is a measurement of how much work you are doing and the rate of speed (how fast) you are doing it.

The benefits of running power are helping you to achieve running faster times, nail pacing during races and also improve running form. That power metric is generated from recording data like record like vertical oscillation and cadence, which we've mentioned above.

Polar is currently the only watch to offer the ability to track running power from the wrist, but there are a host of watches that will let you pair up with suitable footpod to get that hit of data to generate those power readings.

Found on: Polar Vantage V or Garmin and Suunto watches compatible with Stryd

HR Max

Maximum heat rate (HR Max) is the highest number of times your ticker will beat in a minute when you're going all out at your most intense work out level. Your HR Max is unique and depends on your genes and how old you are. The longer in the tooth, the lower your HR Max.

Why is it important? Your maximum heart rate dictates the ranges for all the other zones in heart rate training. The more accurately you know your HR Max, the more accurate your sport zones, and accurate sport zones equal more effective workouts.

There are a number of methods for calculating your HR Max. The most accurate is in a lab, another is using the formula 220 – AGE. In most cases you can manually add your stats into your running watch or they'll also estimate your HR Max based on a fitness test or even a recent workout

So can your improve your heart rate max? In a word, no. Training has little or no impact.

Found on: Pretty much all new GPS running watches

Heart Rate Zones

Using your HR Max, different running watches break down your heart rate zones or 'sport zones' into segments and make them easy to understand with different names or colour coding.

Read this: Understanding heart rate zones

Different devices give them different labels but they break down like this: Recovery training (60% of MHR), endurance base training (65-70% of MHR), aerobic capacity training (75-82% MHR), anaerobic threshold training (82-89% MHR) and maximum aerobic training (89-94% of MHR).

It's worth noting that everyone burns fat, rather than carbs, as a main fuel source at different heart rate levels but having your heart rate zones estimated gives you a far better shot at getting the workout effect you really want to achieve.

Found on: All current running watches

VO2 Max

VO2 max sounds like some kind of complicated chemical compound from a school chemistry lesson but the precise definition is the maximum volume of oxygen (in millilitres) you can consume per minute per kilogram of body weight at max performance.

Read this: A comprehensive guide to VO2 Max

In layman's terms, it's related to your body's ability to consume oxygen. This is important because the higher your VO2 max is, the better the body can deliver oxygen to your muscles helping you to run longer and harder. When you get fitter, your VO2 max should increase.

It's one of the most important running metrics because it can also have an impact on running efficiency and improve form to help prevent injuries.

Just like HR Max, the most accurate way to find out your VO2 max is under lab conditions using expensive gas exchange equipment but many of the best running watches now use intelligent algorithms and a heart rate monitor to estimate your VO2 max based on your vital stats and recent workout performance.

If your running watch supports VO2 max readings, you can get an estimate of your current level by pairing with a heart rate monitor and running outside for at least 10 minutes.

Unlike your HR Max, you can train to improve your VO2 max.

Found on: Garmin Forerunner 245/ Forerunner 645/Forerunner 945/Fenix 6/Polar Ignite

Orthostatic Test

An orthostatic test measures your heart rate for a period while at rest, before doing the same for a period while you're standing up.

From this you get your peak heart rate, standing heart rate and resting heart rate results, which can be used to benchmark your overall condition and how ready to you are to get back out and train.

If your resting heart rate is 10 or more BPM above your average – a sign of overtraining - then you can consider resting.

This is available on some Garmin devices as a stress test – which is separate from the all-day stress tracking metric found in the wellness tracking section.

Found on: Polar Vantage V, Garmin Fenix 6

Ground contact time

Another smart stat you can use to improve your form if you've got a high end Garmin or Polar up your sleeve, Ground Contact time is the amount of time during your running that your foot is on the ground rather than flying through the air.

Measured in milliseconds, a typical runner will have a ground contact time that falls somewhere in the 160 — 300 milliseconds range. Talented types like Mo Farah spend about 190-milliseconds in contact with the ground each step.

Garmin found that there is a connection between injuries and greater imbalances with some runners. Ideally, you should have a pretty symmetrical running form.

It's something closely linked to cadence as well, so as cadence increases, your ground contact time decreases and you should be running quicker. Reducing the ground contact time can also reduce the risk of injury.

So how do you reduce ground contact? There's a few things you can work at like shortening stride length. This is the length of your stride from one footfall to the next.

You can also focus on strengthening glutes and adding some sprint training to your routine.

Found on: Stryd footpod, Garmin Running Dynamics Pod

Lactate threshold

What is your body truly capable of? Measuring lactate threshold is one way of giving us a clearer insight without going through the more complicated process or drawing blood while you're sat on a treadmill inside a sports lab.

It's all about running intensity and endurance here and the process when lactic acid is being dramatically produced in the bloodstream. When you exceed that threshold of lactic acid build up, that's when fatigue starts to kick in and your level of effort or pace is affected.

According to Firstbeat which powers the algorithms that most wearables use to calculate heart rate analysis, the threshold for experienced runners should be 90% of their maximum heart rate. For average runners, it's below 90%. This data is important because it can indicate how much you have left in the tank, whether that's in a race or during an intensive training session.

Firstbeat says it's a useful metrics because knowing your lactate threshold allows you to "personalize all your heart rate zones, which will them enable you to better identify the right pace to achieve your goals."

It's one of the most valuable metrics for runners and while the best methods of testing it are reserved for the lab. If you don't have a running watch that supports measuring it (Garmin watches require an additional sensor), you can do it with an external heart rate monitor and running watch on a treadmill or on a flat road road where you can keep a consistent pace.

Found on: Garmin Forerunner 945 (with chest strap)

Excess post-exercice oxygen consumption (EPOC)

Now we're getting deep into the science. Excess Post-exercise Oxygen Consumption, or EPOC, is the measure of the boost in metabolism (calories and fat burning) your body gets after a workout. Sometimes also know as afterburn.

We all know that when we pound the pavements or bench our own bodyweight, we burn calories to fuel our muscles, but when we're done, we keep on burning, firing and flaying more fat than we would normally at rest. It's all down to what our bodies need to recover from the hard work they've just done.

Some Suunto running watches offer predicted EPOC as a great way to measure the training load of high intensity exercise.

Garmin uses the information for physiological measurements like Training Load. That's where the measurement is used to keep track of the combined strain of all your activities recorded with heart rate data. You can see explainer of how it works in the video above.

Keeping an eye on this number in real time helps quantify the exertion of a training session, giving you the option to stop once you hit an EPOC number.

Tracking EPOC over time also lets you build a good picture of which sessions you personally find more demanding and plan your recovery of training accordingly.

Best running watch to buy: Garmin Forerunner 945 and Suunto 9