**Part 1 – What impact does stride frequency have on energy?**

Running is basically just putting one foot in front of the other and having one foot in contact with the ground at any one time. Nothing complicated so far.

All kids dream of running faster than their friends in the playground and assume that the only way to increase their speed is to lengthen their stride. But are they right?

Usain Bolt is capable of maintaining a stride rate of 240 steps per minute with a stride length of 270 cm!

That’s really quite impressive… but how long can he keep this up? Over 100 meters, he accelerates from the start line to hit a speed close to 24 miles an hour somewhere between 50 and 70 meters. But he can’t maintain this pace so he gradually starts to decelerate.

Athletes in other sports such as swimming and cycling have been looking into this question of stride frequency for a number of years now.

## What impact does stride frequency have onenergy?

Running speed depends on just two parameters: you can either lengthen your stride, or you can increase the frequency with which your foot hits the ground.

**Speed = Stride length x Stride frequency**

To get a better understanding of this equation, let’s consider two extreme situations:

- Imagine you’re running through a paved area and trying to run faster by making sure your feet hit every paving stone. This is a similar exercise to skipping, as it increases your cadence and considerably reduces your stride length. But you would tire very quickly for little gain in terms of speed. Your heart rate would increase with minimal muscular effort.
- In contrast, imagine running with bounding steps. You would abandon this exercise very quickly as it focuses more on the length of your stride than the cadence, and your muscles would soon tire. But this time the increase in your heart rate would not be as high.

So we need to find the right balance between stride length and stride frequency.

Stride length depends on the length of your legs. It makes sense that an athlete who is 5 foot tall will be limited by the length of their steps. In contrast, a runner who is over 6 foot will have a much longer stride.

It’s worth mentioning here the two most common misconceptions about these two different examples :

*“Ah, yes, but they can run fast because they’re short and can take smaller steps!”*

*“Ah, yes, but they can run fast because they have long legs!”*

**Energy cost is measured in milliliters of oxygen consumed per kilogram of body weight to run one kilometer. The lower this value, the more efficient your running.**

When you run with a longer stride, the increased impact becomes a source of eccentric muscular effort. This effort, if repeated over long periods, will cause rapid muscular fatigue and aches that will hamper your progress. Fast-twitch muscle fibers are activated, which although more powerful, are quicker to fatigue.

This is a very common phenomenon among marathon runners, wherecadence is not constant and muscles soon tire. Marathon runners are generally naturally powerful and can utilize this energy, which can be effective over short distances, but which cannot be sustained over long periods of time…

When you run with a higher stride frequency, you have a lighter impact force. Your muscles won’t fatigue as much but you’ll feel a constant increase in your heart rate. But there’s nothing to worry about. You just need to get used to a higher stride frequency for long distances, and you’ll soon notice the benefit. This technique only activates the slow-twitch muscle fibers, which are designed for endurance.

**Higher frequency = smaller steps…**

**But which benchmarks should you adopt?**

There have been many studies conducted on stride frequency and they all converge on the same number.

**Optimal stride frequency: 180 steps per minute**

So there’s no point in ¬measuring the length of your stride! What you need to do instead is focus on your cadence.

180 is the magic number for optimal stride frequency because it gives the most efficient running stride.

**A simple measure of stride frequency is to count the number of times your right foot hits the ground over a 15 second period. Then multiply this figure by 8 to get your stride frequency.**

**Top tip:**

Check out the music website https://www.bpmdatabase.com/ to download tracks with different beats. You can choose tracks with a slightly quicker tempo than your own to help you increase your stride rate. It’s a pretty safe bet that it will be below the optimal frequency, so it’s definitely worth making the effort to improve this aspect to help you progress! Take the test and see for yourself!

By Philippe HERISSON, Xrun Physio

Conception, graphic design : L’Elan Créatif