Instead, your VO2 max is used to identify more useful parameters: your heart rate zones and anaerobic threshold, says Silvano Zanuso, director of the medical and scientific department at Technogym. While VO2 max is a great marker to know – understanding and tracking your cardio fitness can help you set appropriate goals and evaluate your training – no plan or coach would ever suggest heading out on a run at, say, 80 per cent of your VO2 max. A car with a smaller engine has to work harder to go as fast as the big engine,’ says Matthew Meyer, a coach for Mile High Run Club in New York City. Think of it like the efficiency of your own internal engine: ‘A high VO2 max is like a car with a bigger engine. And if you can improve it, you'll run further, faster and longer with less effort and fatigue. Here’s why: when you know what your VO2 max is, you can use that number a precise guide to improve it. Why, then, would you, me, or anyone at all subject themselves to such brutal punishment? Why is VO2 max important?

Imagine your hardest effort, add a claustrophobic mask to measure your oxygen consumption, and then push for one minute longer than you think you can until you’re gasping for air.

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