After a few drinks on a night out, I find the best way to get rid of a hangover is to do a strenu­ous workout because it makes me feel bet­ter. However, my wife says this is a bad idea because I will be dehyd­rated. Is she right?

Your wife is right. Alcohol is a diur­etic: it causes the kid­neys to increase the amount of fluid being urin­ated. If you drink four or five pints of nor­mal strength beer on a night out you might pee out a couple of litres of fluid, along with valu­able elec­tro­lytes that the body needs for good func­tion­ing.

By next morn­ing, the hangover is your best indic­a­tion that you are dehyd­rated. If you had a really late night and drunk a lot of strong alco­hol, you might also still be intox­ic­ated, since it takes the liver about one hour to clear one unit (half a pint) of alco­hol from the body.

Water is the body’s basis for trans­port­ing all its nutri­ents and chem­ic­als around, so a lack of it will make your sys­tem (includ­ing your brain) slug­gish. Studies have shown that doing strenu­ous workouts when you are dehyd­rated sig­ni­fic­antly reduces your car­dio per­form­ance, strength, power, bal­ance and co-​ordination.

The workout itself will fur­ther dehyd­rate you. During a strenu­ous hour-​long workout, you would nor­mally lose 1 to 2 litres of fluid. In your case, the com­bined effect (assum­ing you hadn’t been drink­ing water at all) could leave your body close to the 5 per cent dehyd­ra­tion threshold where ser­i­ous health effects can set in.

So why do you reckon you feel “bet­ter”, des­pite pos­sibly being very dehyd­rated? Your workout may give a short-​term boost to your slug­gish cir­cu­la­tion, which will relieve the hangover fog tem­por­ar­ily, but there’s prob­ably a bit of placebo effect at work, too: if we believe some­thing is doing us good, we tend to feel bet­ter. And in gen­eral, our bod­ies are amaz­ingly good at adapt­ing to cope with all man­ner of abuse –although there is usu­ally a longer term health pay­back.

What is almost cer­tainly true is that your hangover-​cure workout is fail­ing to get max­imum per­form­ance out of your body. Both your car­di­ovas­cu­lar sys­tem and your muscles will develop far bet­ter if they are not con­stantly under– hydrated and over­heat­ing.

The best hydra­tion strategy for an aver­age gym workout would be:

• start off fully hydrated
• drink about 250ml of water 20 minutes before your workout
• drink little and often dur­ing the workout, tak­ing in 1 to 2 litres over­all
• drink another 0.5 to 1litre within the hour after the ses­sion to top back up fully.

Water works very well for nor­mal hydra­tion. Fruit juice will only work if you dilute it with an equal amount of water. “Isotonic” or “hypo­tonic” drinks are fine, but sports drinks (“hyper­tonic”) are energy-​boosters, not hydrat­ors.