I’ll admit that I haven’t done any exercise for a while, but if I start training now, how soon could I be ready to run a marathon?
Jon Andrews, Cheshire

Matt Hart replies: It depends on your present physical condition and how fast you want to complete the marathon. You need to give yourself a minimum of six months to build up your running volume. If you do too much running too soon, your body will break down and you will become overtrained and injured. Start with some manageable lengthy walks interspersed with short bouts of running at the weekend. Then combine these with a couple of short runs during the week and see how you feel.

Set yourself a systematic plan, building up your running mileage weekly until you’re running close to marathon distance three weeks before the event, and then rest up for the big day. Most importantly, if your body is telling you that you’re training too hard and not recovering in time for the next run, listen to it and back off.