Going from hot to cold – say, sauna and ice bath - and back again can reduce pain, banish disease and help you lose weight. And it’s coming to a health club - or beach - near you. Kerry Potter takes the plunge

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I detest being cold – I’m the only midlife woman I know who hates wild swimming and I’d have the central heating on in July if I could afford it. Yet, here I am, merrily plunging into a tub of water that’s a horrific five degrees Celsius. Who even am I? It's only happened because I’ve just spent 15 minutes sweltering in an infrared sauna next to that cold tub, all in the name of contrast therapy. Once I’m done in the tub, I jump back into the sauna and start the process again.

I'm at Rebase, a chic new central London wellbeing centre and one of a growing band of biohacking haunts to offer contrast therapy, the practice of enduring very hot (around 40 degrees for hot water, 80 for a sauna) and very cold (from 4 to 10 degrees) temperatures alternately and in quick succession. With benefits for circulation, pain, metabolism, mood and much more, it’s gaining traction among athletes, wild swimmers and longevity obsessives - and it’s only a matter of time before everyone else follows.

Rebase, which opened in Marylebone in June,  offers contrast therapy group classes – the room has neat rows of baths with a sauna at the end -  plus two private suites with tubs and either an infrared sauna or a traditional one (I plumped for infrared).

Kerry in the infrared sauna (left) and Rebase's contrast therapy class studio (they're baths, not coffins!)

I’ve also given contrast therapy a whirl at the Saltwater Sauna on Sandbanks Beach in Dorset, one of many seaside sauna huts popping up along UK coastlines. Here you switch between hot sauna and cold sea, guided by no-nonsense British Army lieutenant-colonel-turned-sauna-master Jane Witt.

Kerry and her sauna hat (it helps keep your head cool so you can stay in longer) and with sauna master Jane Witt

And now you can retire your ice bath on the patio (so last year!) in favour of a special, at-home contrast therapy tub. I’ve had the pleasure of sinking into the UK’s first all-in-one bath, the stylish Contraspa, custom-made by luxe pool specialists Spaflo. It’s a yin-yang design, with hot water on one side and cold in the other. It’s a thing of beauty – as one might hope when forking out £40,000. You can have one installed in your country pile (alongside your padel court perhaps) or wait for one to crop up at your local fancy health club or spa.

What is contrast therapy?

As any passing Scandinavian will tell you, contrast therapy is not exactly new. It’s always been integral to Nordic sauna culture – you cool off by rolling in the snow or jumping in a lake. It became prevalent in central Europe thanks to Sebastian Kneipp, a priest who researched and popularised various natural alternative medicine practices, in an attempt to cure his tuberculosis. He believed that contrast therapy – he’d switch between swimming in a freezing river and a warm, thermal-spring heated one – helped his immune system. Today at The Ranch health retreat in Italy, there’s a ‘Kneipp bath’ that GTG’s Victoria Woodhall tried - you wade through thigh-deep cold water then hot 10 times to boost circulation. It’s an example of how wellbeing providers are creating convenient, accessible ways of joining the dots between hot and cold therapies, making a practice that’s been around for centuries far easier for people to experience.

Can anyone do contrast therapy?

No – as with using a sauna or doing cold therapy separately, you must seek medical advice if you have underlying conditions. You are double-stressing the body (albeit in a positive way) with two different extreme situations. I would recommend a class or guided session in the first instance.

How do you actually do contrast therapy?

Start with the heat – it’s a more pleasant way to ease in and will make you more likely to endure the cold. On Sandbanks beach, Jane kept me in the sauna until I started to sweat, about 15 minutes, before we headed into the sea. The cold water element of contrast therapy will always be much shorter. I braved the sea for about two minutes, before repeating the process for an hour.

With the Contraspa, I spent about five minutes up to my neck in warm, 37 degree water, then one (at most!) in the 8 degree cold, and repeated this process four times. It’s important to listen to your body and be realistic about what it can endure. I built up my cold exposure very slowly as it’s not something I normally do. I didn’t try a class but I imagine it helps with motivation, especially for cold water refuseniks like me.

A good tip is to finish on a cold session – this burns more fat, as your body has to work harder to heat back up to its normal temperature than it would if you finished in the heat.

If the guided or class options aren’t for you, you could create your own contrast therapy haven at home with an infrared sauna blanket (they start at around £100) and a cold bath.

Kerry trying Contraspa, with its creator Spaflo's Richard Gowland

Is contrast therapy better than doing just cold or just hot therapy?

In a word, yes. You get to reap the separate benefits of both heat therapy and cold therapy, plus the extra benefits of combining the two.

  • The benefits of heat therapy: Alongside the well-documented benefits of sauna use – eg easing muscle and joint pain, helping with sleep and relaxation – new research from the University of California shows sauna use may help with depression. Sufferers typically have higher body temperatures, which lower when they get well again. It sounds counterintuitive but a sauna helps lower our temperature in the long term, as the body modulates its temperature in response to the heat stress.
  • The benefits of cold therapy: The huge popularity of both wild swimming (er, except with me) and the work of ‘ice man’ Wim Hof is testament to the benefits of cold water immersion. “It supports your immune system, reduces inflammation in the body and is great for your cardiovascular system,” says cold water therapist Anna Marie Gough. “And it’s so good for the mind. You can’t start worrying about work or what’s for dinner when you’re in an ice bath. You’re focusing on your breathing.” Immersion in cold water causes ‘hormetic stress’ – a short, sharp dose of healthy stress that’s good for us. “By going to extremes, we are learning to be more adaptable and more resilient,” says Anna. All of which explains why celebrities are obsessed with ice baths. There’s also exciting new research emerging showing a link between cold water immersion and a reduction of Alzheimer’s.

Then we can add to this mix the additional benefits of combining the two in contrast therapy…

What are the health benefits of contrast therapy?

It boosts your circulation

Switching between hot and cold temperatures improves circulation as it encourages your blood to flow in a pulsing motion. “When exposed to the heat your blood vessels vasodilate, pumping more blood around the body,” says Rebase founder Alex Rebeiz-Nielson. “Then when you expose yourself to cold water they vasoconstrict, pulling the blood from the extremities and sending it to your vital organs and tissues. Repeating this process a number of times has the benefit of increasing blood flow around the whole body.”

It can reduce pain and aid recovery

Alex has personal experience of the power of contrast therapy to reduce inflammation, thanks to that improved blood flow. Aged just 25, he endured having his gallbladder and part of his liver removed, a necessary evil after he contracted a parasite while swimming in dirty water overseas. The scar tissue from the surgery left Alex in serious pain – pain that disappeared within weeks of starting regular contrast therapy sessions.

It can help reduce risk of inflammatory diseases

The potential to reduce inflammation has far-reaching benefits. Contrast therapy can “lower risks of physiological and neurological lifestyle diseases where inflammation occurs, such as type 2 diabetes, high blood pressure, cardiovascular diseases, Parkinson’s, Alzheimer’s and dementia, as well as helping with inflammatory conditions such as rheumatoid arthritis and asthma,” according to Jane Witt.

It can help you lose weight

The shock from the hot and cold activates our brown adipose tissue – healthy brown fat. “This warms the body after cold exposure but also continues to burn fat for up to 4 hours afterwards, thereby improving the body’s metabolism,” says Jane.

It helps with longevity

You can see why biohackers are all over contrast therapy. According to Jane: “When you put the body through the complementary micro-doses of healthy stress through heat and cold exposure, damaged cells are repaired so it improves cellular ageing and improves our longevity.”

You feel bloody amazing afterwards

I can confirm: the euphoria is real! Each time, I felt pumped full of endorphins and ready to face whatever else the day might throw at me. For me, part of this was a sense of achievement - contrast therapy has helped me conquer my wimpy fear getting too cold. The heat element makes the cold much more palatable. Jane Witt tells me that beach sauna huts have extended the cold water swimming season for many older, more frail swimmers. Because they can reheat so quickly in the sauna, they can still swim in freezing waters deep into winter. How great is that?

How much does contrast therapy cost?

A contrast therapy class at Rebase is £40, while it’s £150 to rent a private suite (which fits up to three people) for 45 mins – if you don’t like clambering around in public in your swimsuit, this is a good option.

The Contraspa costs just shy of £40,000 – it’s aimed at the kind of people who have gyms and pools in their houses. (It can only be a matter of time before one pops up on a Beckham Instagram feed).

A private guided one-hour bathing ritual with Jane Witt is £175, with a 60 minute communal sauna session £15.

Alternatively, if you're in London you could  try banya, the traditional Russian version of hot and cold therapy, with saunas/steam and cold plunge/ice buckets. The Bath House banya in Belgravia offers a three hour package (including a treatment) for £115, while Banya No 1 (sites in Chiswick and Hoxton) has sessions from £30.

Rebase; The Saltwater Sauna; Contraspa