Worried About Stress Fractures? Look at Your Run Cadence.

Over the many years he’s been a competitive runner, Jason Richwall, a DO candidate and third-year medical student at Rowan-Virtua School of Medicine in Stratford, New Jersey, had listened to his coaches drone on about picking up his run cadence. It seemed every coach had a thing for fast feet, but they didn’t always have a good, scientific explanation for why they were giving that advice.

Eventually, Richwall, who ran cross-country and track at Muhlenberg College in Allentown, Pennsylvania, and ran for a season at Rowan University while working on his Master’s degree, wanted to know why exactly cadence was such a big deal. So when it came time to complete a research project as part of his medical degree, Richwall dug into the literature and found plenty of evidence to suggest that his coaches had actually been right all along – even if they didn’t know why.

“Across the board, virtually all of the studies I looked at suggested that quicker running cadence or shorter stride length are correlated with lower risk of occurrence of injuries,” he says. Specifically stress fractures, which are called bone stress injuries these days, declined when cadence increased.

But why does a faster cadence reduce injury risk? “A lot of it has to do with force,” says Milica McDowell, DPT, certified exercise physiologist, and vice president of operations at Gait Happens, a group of clinicians focused on foot health education and resources to support efficient movement.

The force is (pushing) against you

It might seem a little counterintuitive at first, but fast, light feet really can reduce the impact on the lower body during running. That’s because every time your foot strikes the ground, not only is your body pushing down against the surface, the surface is also pushing back on your body. This is called ground reaction force and is exactly what Sir Isaac Newton was talking about when he jotted down his third rule of motion – the Law of Action and Reaction.

This law states that for every action, there is an equal and opposite reaction. So, whenever one object exerts a force on another object, the second object exerts an equal and opposite force on the first.

This is important because while increasing cadence means your foot is striking the ground more frequently in a minute, “you’re actually spending less time in contact with the ground,” McDowell explains. Though each strike might be just a millisecond shorter, over the course of thousands of steps during a long run, that time adds up significantly.

This in turn decreases the amount of load your body experiences as you run and the amount of ground reaction force your body must absorb in return.

That force depends in part on your mass, or how much you weigh. A lighter runner exerts less force on the ground and gets less force in return than a heavier runner. Acceleration also comes into play – sprinting creates more force than lightly jogging. Bone strength is also a factor; bone stress injuries occur when the strength of the bone can’t match the amount of stress being placed on it.

McDowell gives the example of banging on a drum hard versus banging on it lightly. “If you were trying to make a really loud noise, you’d strike it really hard. But if you’re trying to make a softer noise, you might strike it more softly so you don’t get as much impact.” And if you hit it with all your might or use an object that concentrates that force into a smaller point, you could break the drum, which in this example represents your bones.

With a faster cadence, you’re also minimizing some of the biomechanical angles, which changes how quickly the load of your body mass goes through your bones. This was demonstrated in a 2018 study in the Journal of Biomechanics, the gold-standard publication for kinematics.

Adjusting your stride length can also reduce risk of injury in some cases, though McDowell emphasizes that there’s a difference between cadence and stride length. “Cadence is the number of strikes per minute,” while stride length describes the distance you cover with each step.

“Now, it’s pretty common to say the faster you turn your legs over, the more it shortens your stride,” she notes, but the two don’t always go hand-in-hand.

That said, shortening your stride can prevent overstriding, “which is where people are running like they’re jumping over a puddle and really extending those legs out – this is not efficient,” McDowell explains, and adds that it can lead to a range of injuries from shin splints and stress fractures to runner’s knee.

How to increase run cadence

The first step toward improving your cadence is figuring out what your natural baseline cadence is, McDowell says. “In order to do that, you need to be your own research guinea pig.”

Set a timer on your watch for 60 seconds and count every right leg strike while you run comfortably. Once you’ve got a number, multiply that by two and it will tell you how many steps you’ve taken in a minute. (Some smartwatches can calculate this for you, though accuracy may be a concern.)

Repeat this exercise a few times over a couple of workouts to check that you’re getting consistent readings.

Once you’ve got that number, then it’s time to start nudging it up. McDowell recommends downloading a metronome app and setting it for your desired cadence. Match your foot falls to the beat of the metronome.

The key is to adjust slowly over time. “You can’t just cold turkey go from running at 160 and try to run at 185,” she says. So, if your baseline cadence is 160, which McDowell says “is a little slower than optimal,” you can work on increasing it for a minute or two at a time before dropping back down to your baseline. It’ll take some time, but keep at it; eventually, the higher cadence will start to feel normal.

While many people’s natural cadence falls somewhere in the neighborhood of 170, aiming for a cadence above 180 has been shown to be effective for reducing injury risk in long-distance running. But it’s not a magic number: Cadence is an individual thing and you should play with it to find what’s optimal for your body.

In addition, “if you’re a sprinter, this does not apply because sprinting and running are completely different, just like running and walking are completely different,” McDowell says. But if you’re aiming for a 5K or a marathon, “you want to think about being efficient,” she says.

It’s also important to keep in mind that increasing cadence does not automatically mean your running speed will increase, but you may be able to reach the finish line with a little less wear-and-tear on your body – and you may be able to train with greater consistency, over longer distances to build better race-day gains.