Sauna benefits: how long and how often.

You check in at seven in the evening with a flight and two meetings behind you. There's a spa downstairs, and you wonder whether sauna benefits are real or just a pleasant way to sweat.

People I work with often ask me this. Nearly all use it the same way: now and then, for as long as they can bear. Short and often works better.

What are the benefits of a sauna?

The best-studied one is for your heart and circulation: heat works them much as moderate exercise does. Recovery and sleep come next, if you pick the right time.

• Heart and vessels. Your heart rate climbs and your vessels widen.
• Recovery. Your muscles loosen and many come out less stressed.
• Sleep. In the evening it sets up the drop in temperature that helps deep sleep.

What happens in there

Cardio without moving. To shed heat, your body sends blood to the skin and your heart speeds up. With repetition your vessels tend to stay healthy, and your cells make proteins that help protect tissue.

The heart figure. In a large Finnish comparison, using a sauna four to seven times a week was linked to around 40 per cent fewer heart deaths than going once. It's an observation: a link, with no proof of cause.

What you lose is water. The weight you leave in there is back once you drink. Sweat cools you, and to sweat you only need heat, no effort. A sauna adds to your training.

Short of water, it's worse. After a day of coffee and little water, your body tends to rein in sweat too, its cooling system. You heat up more, your blood thickens and your heart works harder.

Sauna: how long, and how many times a week?

Fifteen to twenty minutes, at 80 to 90°C in a Finnish sauna. Two or three times a week is a realistic habit at the gym or a hotel. In the studies, the best figures are for people who go more often, four to seven times. Stop at ten minutes the first few times.

Too hot? Try infrared. Dry heat, around 60°C. It's usually easier on your heart and blood pressure, and nearly everyone tolerates it. With a heart condition, doctor first.

Sauna after a workout. It helps loosen your muscles. You've already sweated, so drink before you go in. Skip the cold straight after weights; the cold shower article explains why.

In the evening, for sleep. Finish an hour to an hour and a half before bed. Once you're out your body sheds heat, your core temperature falls, and that's a signal for sleep. Skip a cold shower afterwards; at night it tends to wake you.

What to drink. Water: a glass before and another after. Salts only if you sweat heavily for a long time. Keep alcohol away straight afterwards too. It makes you lose more fluid.

Next hotel sauna: fifteen minutes, water within reach. If you sleep better that night, you've found your time.