On the surface, running may seem simple: you put one foot in front of the other at a pace somewhere above walking speed and hope for the best. But dig a little deeper into what makes a ‘good’ runner, and you’ll soon discover it’s just as technical as any other discipline; from cadence to vertical oscillation, running can quickly become a game of numbers.

And one number tends to come up time and time again in conversations about running ability: VO2 max. A measurement of the maximum amount of oxygen your body can use when you’re pushing yourself to the limit, VO2 max is an indicator of aerobic fitness, which means it tends to positively correlate with running performance. As such, many runners pride themselves on having a high VO2 max (most fitness trackers and watches measure it) and focus on improving theirs in a bid to be a better runner. 

But is VO2 max really the metric we should be focusing on, or are there other, more important numbers that we should be paying attention to? To find out more, we spoke to Holly Page, a professional mountain and trail runner and Adidas Terrex athlete. 

Most runners (sprinters aside), rely on their aerobic energy system to keep them going, so it makes sense that VO2 max – a measure of aerobic capacity – is a valuable measurement.

“VO2 max measures how efficient your cardiovascular and muscular systems are in delivering and using oxygen to produce the energy you need for running over a sustained period of time,” Page says. “It’s particularly important for endurance events; if you have a higher VO2 max you can run at a higher intensity for a longer period of time without getting fatigued because your muscles have more oxygen.”

Our muscles use oxygen to create energy, which allows them to contract in the way we’re asking them to during a run. When they don’t get enough oxygen – ie when we surpass our VO2 max during short, intense sprints – they switch over to the anaerobic energy system, which uses glucose to produce energy (alongside lactic acid). But our muscles only have a limited store of glucose (known as glycogen), and once this runs out, they begin to fatigue. It’s at that point when you’ll find you can’t run any further without taking on external fuel to top up those glycogen supplies.  

In this way, a strong VO2 max is important because it stops your body from switching over to that anaerobic energy system. Oxygen is a practically unlimited energy source, so you want to keep your body in that aerobic state to be able to perform at your best.

It’s important to note that having a higher VO2 max isn’t just beneficial for running. Being cardio fit means you’ll be able to run for a bus more easily, find it easier to take the stairs and enjoy better health more generally. 

VO2 max is important, but it’s far from the only thing runners need to think about if they want to improve their performance. “There are so many factors which feed into running performance,” Page says. “Factors such as running economy, strength, mental resilience and technique on mixed terrain (especially in trail running) all play an important role, as do strategy and experience when it comes to racing.”

If you want to improve your physical performance, your VO2 max, running economy and strength are probably the three most important factors to start with.

Running economy is a blanket term that refers to the amount of energy your body uses to run a specific distance. In a lab, it’s measured by tracking the amount of oxygen you take in while running at a steady speed, but fitness trackers like Garmin measure it based on the number of times your heart beats while you travel a certain distance.  

Running economy is made up of everything from your cadence and vertical oscillation to stride length, metabolism and muscle stiffness, so it’s a real all-rounder.

Strength, on the other hand, is more straightforward. Bigger, stronger muscles will fatigue less easily and produce more force with each stride, allowing you to run faster for longer. Stronger muscles also absorb force more easily, reducing your risk of injury. 

It’s natural to want to improve your running, but obsessing over one number or metric and spending months trying to see a change probably isn’t the most effective (or enjoyable) way to see progress. Your best bet is being aware of your weaknesses but taking a more balanced approach, Page says.

“Work out where your weaknesses are and then decide on a strategy as to how you can incorporate improving these into your different training sessions over a longer period of time,” she says. “There’s no reason why you can’t try an all-around approach where you try to work on different aspects across different training sessions.”

For example, if you want to improve your VO2 max and running economy, you could alternate between long, slow easy runs (where you focus on your cadence and breathing techniques to improve running economy) and interval sessions (where you push yourself hard to improve VO2 max).  

If you’re not sure where to start, there are plenty of free running resources online. Joining a running club or consulting the advice of a running coach can also give you the information and space you need to improve.

But the key, Page adds, is keeping things as simple as possible. It’s easy to get confused by all the terminology and numbers, and getting bogged down in the details can take its toll on your mental state, which can then affect your running.

“Trying to change too many things at once will likely lead to you feeling overwhelmed and make you lose motivation,” Page adds. “Remember that you run for enjoyment and to feel good – you don’t need to overcomplicate it!” 

Images: Getty