The benefits of running slowly

After Cambridge Half Marathon I tweeted: “To anyone scared to run slow, I do a lot of my miles at 10:00+ min/mile pace and today ran 7:44/mile for 13.1. Don’t be afraid to slow down.”

While I did a weekly threshold run and some shorter intervals, much of my training miles were clocked up at a pace much slower than my race pace.

Slow or ‘easy’ runs are a commonly misunderstood element of training. They’re the part of the plan that some runners get wrong by ignoring the pace or perceived effort level they’ve been told to run at, thinking instead that if 10 minute miles are good, 9 minute miles must be better right? Wrong.

Why that’s wrong is a big topic and I’ve tied to keep this as simple and brief as possible. Here goes…

A better running body

Running slowly encourages more mitochondria to develop in your cells, and promotes bigger mitochondria. This is a very important adaptation as these little fellas are where the energy in fat and glycogen (carbs) gets turned into something your body can use to run (ATP).

It also encourages greater capillary density, so oxygen can get to the cells of your exercising muscles more readily. It helps improve your VO2 max (how much oxygen your body can transport and use while running), and develops a better running economy (how fast you can run at a set amount of oxygen). All good stuff.

Better fat burning

This isn’t a weight-loss thing, so don’t think that it doesn’t apply to you because you’re not interested in losing weight. This is a fueling thing – as in what fuel your body uses to run.

Very simply, your body runs on both fat and glycogen (from carbs) – just like your house might be powered by both gas and electric. The percentage of fat and glycogen that are powering you at any given minute will depend on the intensity of your activity. So sitting down reading this, you’re powered more by fat, but stand up and jump up and down for a few seconds and more glycogen will come into play.

You might flick the kettle on and use electric to heat enough water for a cup of tea but it’s not the most efficient way to fill a bath. For that you need your gas boiler.

Running at an easy pace teaches your body to burn fat over glycogen for fuel. Which is handy because even a slim person has enough body fat to power them through 500 miles of running, but running on glycogen alone they’d struggle to get much beyond a half marathon.

More miles and fun miles

You can’t so all your miles at break-neck speed. Running some of your runs slow allows you to increase your training volume (number of miles per week) with less risk of injury and burn-out. The figure commonly banded around right now is 80/20, so you run easy 80% of the time and run fast (so your higher intensity runs including speedwork and tempo runs) 20% of your schedule. I think this is a little prescriptive for every level of runner, but it gives you an idea.

One of the biggest benefits of running slower (for me) which has nothing to do with physiological adaptations is that I have more fun running slowly sometimes. I’m able to run with slower runner, I’m able to potter along and enjoy the scenery and I’m able to chill out – and we all need more of those runs in our week. It’s good to know that they’re providing some training benefit too though.

How slow is slow?

Speed is relative, so while my ‘slow’ miles are around 10 mins/mile, to another runner this would be their goal 5k pace, but my 5k pace is probably a cool-down for faster athletes. As a rough guide though, I’d say that easy runs should be 1-2 mins slower per mile than marathon pace. For those targeting shorter races it’s a couple of minutes pre mile slower than race pace, you should feel comfortable holding a conversation while running and not out of breath.

‘The Strava problem’

We’re impatient. We want to see improvements in our running straight away and we worry that training isn’t working. It’s understandable. 12 or 16 weeks is a long time to work towards a race, but your training cycle is that long for a reason – because that’s how long it takes your body to peak. Trust the process.

It’s tempting to test yourself, to go out and try to run at race pace more than you’re supposed to, to try to get a parkrun PB on a Saturday morning when that’s not in your plan or to try and get a few Strava segments when you’re out on your easy run. And then there’s the competitive element between runners – “my friends follow me on Strava, I must run a bit faster so they don’t think I’m slow”. Forget it all.

I quite proudly log my 11 minute miles on Strava, and I don’t care who sees it. In fact, I think it’s important for my runners to be able to see the variation in speeds that I run throughout the week so they know that I’m practicing what I preach. So when I say that there were a lot of 10 min miles that went into training for that 1:41 half marathon, you don’t have to just take my word for it. You can see the data.