WHAT HAPPENS WHEN...

That 7am boxing class seemed like a great idea, before last night happened. So, what’s really going on when you follow a gin with the gym?

...you do HIIT on a hangover

1 HIIT THE HAY

Feeling drowsy? That’ll teach you. Even if your carriage (read: Uber) delivered you to your bed before midnight, your sleep quality will have suffered. A study published in JMIR Mental

Health found that even a session of moderate drinking lowers restorative sleep quality. ‘Working out when tired can increase your risk of injury – hamstring injuries often occur when a tired person tries to sprint,’ says Dr Leon Creaney, consultant in sport and exercise medicine at the Manchester Institute of Health & Performance. ‘Fatigued muscles can’t react as quickly either, so your coordination and agility are compromised, too.’ So, be sure to watch your step on the treadmill.

2 THIRSTY THURSDAY

As in the day after

Wine Wednesday. In fact, for every 1ml of alcohol drunk, urine excretion increases by 8ml*, so, unless you were reaching for H2O as often as you were your debit card, you’ll be dehydrated before you’ve even thought about getting a sweat on. ‘While moderate dehydration hasn’t been found to impair performance during exercise, severe dehydration has been linked with poor concentration and fatigue, which can lead to cramps, strains and injury,’ says Dr Creaney. Drink up.

3 SWEAT IT OUT

It’s a real thing. Around 10% of the alcohol that isn’t metabolised is expelled via sweat, urine and your breath. But don’t rely on it. ‘Dehydrated kidneys work extra hard to preserve water – and your body will reduce the amount you sweat to aid this,’ says Dr Creaney. So go too hard in the gym and you risk becoming even more dehydrated.

4 MUSCLE MEMORY

Your goals last night included the Golden Arches, but if you’re in the market for muscle the next day, take note. ‘Muscle development is directly impacted by alcohol, and fast-twitch muscle fibres – most responsive to resistance training – are especially affected,’ warns Virgin Active PT Jason Jackson. ‘Fat-burning takes a dive, too. Drinking just two units of alcohol suppresses it by 73% for several hours.’

5 THE SHAKES

Nope, not a dance move, but a reaction to low blood-sugar levels. ‘Alcohol interferes with the liver’s ability to keep blood-sugar levels steady,’ says Jackson. Balance your blood sugar by eating a piece of fruit 30 minutes before you work out. Feeling sick?

Opt for a low-impact class and drink some hot water with 3g grated ginger root beforehand, which has been found to reduce nausea symptoms*.