Marathons require a lot of mileage, with the key session of each training week being a long run. Can this be split up and made into two runs? How can it be done in the best way? Let’s find out.


Why you might want to split the miles

As discussed in a previous blog on how long your longest run should be, we want to be around 20 miles or 3 hours, meaning that if you’re looking to run a marathon in around 4hrs 30 minutes, you might want to split the long runs. 

Time can sometimes be an issue as well, leading to more occasional splitting of long runs as a way to maintain weekly mileage whilst squeezing runs into the time you have available.


Keep the mileage up

Studies have shown that one of the biggest predictors of faster marathon times is the average number of weekly miles in training. If you’re looking to run a faster marathon then, splitting the miles can be a viable option if it allows you to run more miles overall. I’d make sure you do at least a couple of larger long runs though, in part for the confidence in your ability to keep going, but also to better prepare your body.



If you’re on the way back from an overuse injury, running more frequently for shorter periods of time/distance can be a way to manage a return to full training. In this situation, under the guidance of a qualified professional ideally, splitting long runs can be a way to maintain overall volume of training, whilst keeping injury risk as low as possible.


How to split long runs

You can of course split what would be the long run mileage in half, making a 16 mile run into two 8 mile runs. Whilst there’s some merit to that, two runs at the same pace will be less interesting/enjoyable and less beneficial if both are done at the type of pace you’d run a continuous long run. Alternatively you could do one harder 8 miles, and an easier 8 miles, but in theory you’ll already be doing 1-2 interval or tempo style runs in your training week anyway, meaning a hard and easy split could pose a higher risk of injury.


My advice would be to run as long as you can in the first run with a more effortful pace, then perform the second run at an easier level. 16 miles could then look like this:

Run 1 – 10 miles with 4 miles at marathon pace. 

Run 2 – 6 miles at marathon pace plus 45 seconds/mile


Run 1 – 12 miles with 2 round of 3 miles at marathon pace

Run 2 – 4 miles at marathon pace plus 45 seconds/mile


With regards to timing of the two runs, you can either split them across two days, or perform a “double run” day, getting out in the morning and evening instead. Personally I’d lean towards two days for safety and better recovery, or if you’re looking to push the body a tiny bit more, an afternoon or evening for run 1, then a morning for run 2. This reduces the recovery time and will at least in part simulate the feeling of running when your legs are a bit tired. Something a marathon will always cause in the latter miles.


Splitting your long runs isn’t something I recommend as a first option generally, but in certain situations it can be a good or even the most sensible option. Do what you need to in order to get good quality training appropriate for your circumstances and goals. 


Written by Kyle Brooks, Running Coach based in Norwich, Norfolk