It’s common knowledge that you should change out your running shoes every few hundred miles.
At least, that’s what the guidebooks and shoe retailers tell you.
Being used to running in fairly minimalist shoes, I was a little skeptical that a pair of worn running shoes could make that big a difference to your performance.
Therefore, I decided to test this piece of accepted wisdom with a study of my own.I dug out an old, worn pair of shoes and went for several 5km and 10km training runs in them, measuring my heart rate and effort along the way.
I then got some brand new shoes with similar specifications and repeated the test several times.
Here’s what happened when I tested the performance difference between old and new running shoes!
The Old Shoes: New Balance 1400 V2
I’ve used these shoes on and off for the past 3 years. They were typically my ‘back-up’ running shoes, and I would bring them with me when I travelled or was out of training.
I’d estimate I’ve put 400-500km into them. I’ve also used them for a lot of beach running, and running in hot, humid climates – so they’ve lost some of their form. Recently, I’ve just been using them for gym shoes.
Description: Lightweight, low-cushioning shoes that are so old I don’t remember buying them.
Kilometres Run: 400 – 500km.
The New Shoes – Nike Flyknit Free RN
I’m a huge fan of the Nike Free range, as they’re generally quite minimal but still comfortable.
The Flyknit models are always super comfortable, and I find them suitable to wear for pretty much any occasion.
I chose these shoes for this test as they are similar in support, drop and design to the New Balance shoes, and not quite as performance-oriented as a model like the Pegasus. When I started this test, they had covered less than 20km of running – so practically brand new.
Description: A neutral road shoe, with just enough cushioning to make this minimal shoe super comfortable.
Kilometres Run: <20km.
The Test Environment: Retiro Park, Madrid
I’m lucky enough to be able to run in Retiro Park in the centre of Madrid very often – it has a perimeter of around 4km and loads of intersecting paths and trails – so I decided it was the perfect location to do my trial.
This means that every run was conducted in the same location, at similar times of the day, with similar conditions.
The Test Conditions: 5 – 10km Runs
In order to compare like-for-like, I ran several 5km and 10km runs through Retiro with each pair of shoes. (I tracked every run using Strava via my Apple Watch.)
Once I started monitoring my runs in both pairs of shoes, it was soon apparent that the newer shoes made a notable difference to my performance. I felt faster, and could see the difference on my running pace.
Not only that, but the newer shoes made running easier – they were simply more comfortable to run in, which encouraged me to run faster.
The following results are taken from my Strava account:
Two main things jump out at me immediately.
The first is that obviously my speed has improved. While I took around 51-53 minutes to run 10km with the old shoes, the new shoes have me doing the same distance in 45-47 minutes.
That’s a 19% improvement in speed.
On it’s own, it sounds quite impressive – change out your shoes and you can increase your speed by 19%.
But that’s not the full picture . . .
My Relative Effort has also increase, as you’ll notice above.
Relative Effort is a metric Strava works out based on your heart rate data; as you can see, my Relative Effort when I was running in new shoes was much greater than when I ran in the old shoes.
How to explain this?This wasn’t a conscious thing on my part – although it may look like I was pushing harder when running in the new shoes in order to make them look better, I wasn’t intentionally doing this at the time. Instead, the new shoes made me feel like running faster.
When I ran in the old shoes, the lack of spring and shoe structure seemed to sap my drive. I could have pushed harder at times, but it felt more of a slog – like hard work. The new shoes had the opposite effect.
Their support and motion encouraged my running form, driving me forward like a train.
In longer runs, it’s possible that this would have sapped my energy faster – but in this scenario I could just pace myself to allow for the increased push.
There’s no doubt that the newer shoes made me run faster – 19% faster, in fact.
However, it’s also clear that I was pushing harder during these runs. But this wasn’t a conscious effort – I was running at the pace I felt comfortable at, dictated by the shoes.
Have you noticed a difference in your running performance after changing out your running shoes?
Leave a comment below!