Sports clinic

Our experts sort out your health and technique problems
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Lying in bed I often get bad cramps in my calf muscles and instep. Why is this, and why do some people seem more susceptible to cramps than others?
Peter Carter, Solihull

The cause of cramps is still not fully understood, but it is known that dehydration can provoke muscle spasms. It is easy to become dehydrated without realising it, since you only feel thirsty once you are already two per cent dehydrated. Check that your urine is pale, an indicator that you are taking in enough fluid, and drink before you feel thirsty. Other causes can be minor muscle injuries or impaired circulation; the result of tight socks, a cold or other infection. Most people know to stretch out a cramped muscle to relieve the pain and spasm. Quinine sulphate is an effective treatment for night cramps, but it is better to avoid all possible precipitating factors before resorting to regular medication.

My village cricket team has some good players, but we're a bit of a rabble when it comes to fielding. What can we do to improve?
Peter Milton, Somerset

Fielding is an aspect of the game too often underrated and underpracticed. All-round fitness is obviously important, but so is warming up and warming down; suddenly having to run at full gallop after standing around can lead to pulled muscles. Having the entire team on the outfield 10 minutes before the start, throwing the ball to each other at various heights and speeds, is a good discipline to get into, as is practising getting down to the ball with the body behind it when ground-fielding. When catching, always get two hands to the ball where possible; and in the deep, if in doubt "under-read" the ball – it's always easier to adjust by going forwards than by back-pedalling.

I often swim several laps of crawl and then a lap of breaststroke as a resting stroke, but I've heard it's bad for your joints to change stroke. Is this true?
Felicity Lewis, by e-mail

First of all, it is worth remembering that swimming is an extremely safe sport, with only 0.4 injuries per 1,000 hours. This compares to four per 1,000 in football and one per 1,000 in rugby. In general, cross-training helps to reduce injuries, and there is no evidence that changing stroke causes damage. Swimmers do get overuse injuries, though, especially around the shoulder, and there is an injury called "breaststroker's knee", a strain of the ligament on the inside of the knee. So build up the volume and intensity of training sensibly and carefully. Within this framework, switching between different strokes offers variety that may actively encourage you to keep swimming.

Richard Budgett, medical director of the British Olympic Association, led this week's panel of experts

Send your questions to: Sportsactive, The Independent on Sunday, Independent House, 191 Marsh Wall, London E14 9RS; or e-mail: sportsactive@