I'm thinking of signing up for a marathon, but I'm not sure how much time it will take to train. I regularly run about 10-15k, so how long should I give myself before I sign up?

The good news is that you’re not starting from scratch and by the sounds of it you’re already well on the way with your training! You’ve built up an excellent base, so unlike many people embarking on a marathon adventure, some of the hardest work is already done. However, you’ve right to think hard about your training plan, as you’ve still got work to do.

According to most experts marathon training plans will range from 12 to 20 weeks. And you should be looking to build your weekly mileage up to 50 miles over the four months before the big event. Three to five runs a week is ideal – taken at an easy pace. This is called building your base mileage. But take it gradually – don’t increase the miles you’re tackling every week by more than 10 per cent at a time.

Coupled with this, it is important to build up your weekly long run by a mile or two each week. Every three weeks scale it back a bit so you don’t overstretch yourself. Remember this process really is a marathon and not a sprint! Building your weekly mileage too quickly puts you at higher risk of injury – and that can be devastating for your marathon training programme. Running a few shorter races over your existing distance – or even a half marathon – is a good way of building up to the big run. It can prepare you both physically and mentally for the challenge ahead.

It’s also important to remember that your training doesn’t have to be record breaking and that it is all about consistency. For half marathon and marathons you should aim to have covered around 75% of the total race distance at least once in training. And there’s no harm in getting started early with your training plan. The key thing is not to do too much too soon.