Increase your distance and get marathon fit with personal trainer Jeff Archer’s top tips to tackling 26.2 miles

how to go from half marathon to full marathon Men's Fitness UK

Give yourself at least a couple of months to build up to around 20 miles in training

How long will it take to go from half marathon to full marathon?

If you increase your long run by no more than ten per cent per week, you can work up to the full distance within a couple of months. It’s a good idea to allow ten to 12 weeks, to give yourself plenty of time for some vital rest and recovery, and also enable you to include a selection of cross-training sessions that will help minimise the risk of injury as you steadily increase your mileage.

How many runs should you aim for each week?

Everyone responds differently to various training loads, but you can do it on just three runs per week. One of these should be a long run, which will probably be at the weekend. One will be either a hill training or interval training session lasting 30-45 minutes, and the third will be a tempo run of anything between 45 and 90 minutes.

For shorter runs, these bursts can be at a higher speed and of a shorter duration – say one to two minutes at a quick pace with three to five minutes recovery. During longer runs, you might mix up five to ten minutes running faster than your comfortable race pace combined with five to ten minutes of recovery.

Do you need to run every day?

No, there’s no need to run every day. For the majority of your training schedule, it’s best to ensure that you build in a day or two following each run to recover. Always keep in mind that your fitness and strength adapt and improve following a training session rather than during it.

That said, a marathon is a long race and you probably won’t be running the full distance during your training so running on consecutive days can be a good idea. Experiment with this by scheduling a short recovery run the day after your long run. This can be a slow pace.

At some point in your schedule, it can be effective to run on three, four or even five consecutive days, which is fine as long as you allow the same number of recovery days following each block of running.

How to go from half to full marathon Men's Fitness UK

Mix up your training with low-impact activities like swimming to maintain fitness while reducing risk of injury

How much extra time do you need to allocate to your training each week on average?

There will be some weeks where you might want to add 15, 30 or even 45 minutes to a hill training or tempo session, and the time required for your long run will certainly increase, but that will be most noticeable from around the halfway point of your schedule.

The greatest increase in the time you require could come from adding some cross-training to your schedule. You can add this training either as a 45 to 60-minute session periodically, or you can build elements of strength training, stability, core work and stretching into your daily routine. 

Should you consider getting another pair of trainers?

Some runners like to use different trainers for running on different surfaces. It can be helpful to use lighter trainers for sprint intervals, hill training or any track running that you do, and a more robust shoe for trails or longer distances.

However, whatever you do, don’t race in new shoes. If you must get a new pair before the race, make sure you’ve worn them in for at least three weeks beforehand.