What Happens to Your Lungs When You Ride

There’s a reason fitness is measured in terms of VO2 max, the highest rate of oxygen your body can consume during maximal or exhaustive exercise: To perform physical activity like riding a bike, especially if you want to go far and/or fast, your body needs to consume a lot of oxygen. The more oxygen you can circulate to burn fat and keep your aerobic energy production churning, the longer and faster you can ride without fatiguing.

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“VO2 is a function of how efficiently you breathe,” says Paul W. Davenport, PhD, distinguished professor in the Department of Physiological Sciences at the University of Florida, who specializes in the study of the respiratory response to exercise. Which, of course, is where the lungs come in. Here’s how they work.