Sleep is your best recovery tool. Here's how to protect it.

Every goal on this site — stronger, leaner, better skin — depends on sleep more than on any product or programme. It's also the thing most people trade away first.

What happens when you're short

• Muscle. Sleep restriction reduces muscle protein synthesis and raises cortisol. In one study, dieters sleeping 5.5 hours lost 60% more lean mass and less fat than those sleeping 8.5.
• Appetite. Short sleep raises ghrelin (hunger) and lowers leptin (fullness). People reliably eat more, and more of it is high-calorie.
• Skin. Growth hormone and cell turnover peak during deep sleep. Chronic short sleep is associated with more visible signs of ageing and slower barrier recovery.
• Training. Reaction time, coordination and perceived effort all worsen. Injuries in adolescent athletes roughly double under eight hours.

How much

Most adults do best on seven to nine hours. If you need an alarm every day and feel drowsy in the afternoon, you're probably under.

What reliably helps

1. A fixed wake time, including weekends. It anchors your body clock more than bedtime does.
2. Morning daylight, ten minutes outside within an hour of waking.
3. A cool, dark room — around 18°C, with as little light as possible.
4. Caffeine cut-off roughly eight hours before bed. Its half-life is five to six hours.
5. Alcohol moved earlier or reduced. It sedates, then fragments the second half of the night.
6. Screens down, not for the blue light so much as for the stimulation.

On the nights you can't

Don't try to "make it up" with a long lie-in; keep the wake time and take a 20-minute nap before 3 pm if you need it. Train, but lighter — reduce weight or volume rather than skipping. And stop worrying about the occasional bad night; it's the pattern that matters.

What to do this week

• Pick a wake time and stick to it for seven days.
• Get outside first thing.
• Move your last coffee earlier by an hour.