When you begin running, the temptation is to look at long distance and marathon runners and immediately want to jump to their level. We think the challenge will be for our cardiovascular system to take the strain of a sudden increase in mileage, but it is actually the muscles and tendons that will give way first! Put simply, one's body needs to gradually 'learn' how to handle long distances.

So what kind of learning curve are we talking about? Running experts may disagree on different approaches, but as a starting rule there appears to be near-unanimous consensus: each week, the mileage should increase by around 10%, and this should not happen with a concurrent increase in speed. Either the distance or the pace increases, but not both. When training for a race, there are a number of different opinions on when in your training you should aim for speed increase and when to aim for distance increase, a debate allaboutrunning.net hopes to cover shortly.

10% is a good ballpark figure to keep in mind: the actual level, however, will vary slightly from this on what your current weekly mileage is. It is easier (and safer) to increase a 10 mile-per-week schedule to 11 than it would be to increase a 90-mile a week to 99! So you can create a sliding scale of sorts, from 15% at 10 miles per week all the way down to 5% at 100 miles per week.

When increasing your mileage, it is probably best to apply this increase to some of your runs whilst keeping the other 'recovery' runs at the same distance. Many runners have one 'long run' a week which is considerably longer than their other runs and which they view as the focus of their mileage increase; this run invariably gets increased every week by force of habit, but it is no harm every few weeks keeping that run at the same length and putting the mileage increase on the shorter runs.

Also, there should not be a steady linear increase in mileage every week. Some experts recommend increasing the mileage one week, and then running the same mileage for the next couple of weeks to let the body adjust. Others advocate having a 'recovery' week every 3-4 weeks where you perhaps run 2/3 of your current distance on your long run; next week you can then pick up with the mileage increase where you left off. The first approach probably works better for those who are just seeking to work their way up to some base mileage, the second would probably suit someone who has that base mileage under their belt and is training with a race in mind.

Of course, keeping yourself to a percentage weekly increase is no guarantee of injury prevention. Whilst running, listen to your body; through experience you will come to distinguish transient aches and discomforts from pains that suggest something might be badly wrong. In fact, the 10% rule (and all rules like it) are only guidelines that are there to help you until such time as you can successfully implement the golden rule of listening to your body through experience.