HEAT SEEKING

Onsens, saunas, hammams, and similar heat therapies are some of the oldest wellness treatments in the world—but do they still have a role to play today?

It’s -4°C in Niseko, powdery snow is blowing almost sideways, and I’m about to step outside—totally naked.

I’m at one of the hundreds of outdoor onsens that dot Japan, where locals and tourists alike slip into pools of hot, cloudy water that’s naturally heated by volcanic rocks deep underground. Tales of the miraculous powers of these baths have been told for centuries. More than 3,000 years ago, people in Matsuyama are said to have seen an injured heron return day after day to bathe in a hot spring until it was healed, and Japanese legends claim brave samurais recovered from their battle wounds after a long soak.

They may sound apocryphal, but it’s likely these stories contain a grain of truth. Scientific studies suggest onsens improve circulation and sleep, lower blood pressure, ease pain, and generally boost human health. During last year’s Rugby World Cup, teams from around the world took to onsens after their matches, hoping the water would heal their battered and bruised bodies. Then there are the benefits to mental health—bathing in hot water is said to relieve anxiety and reduce stress.

But to experience this for myself, I have to brave the cold. Outside, three large baths of differing temperatures line a trail of wet stepping stones. I crack open the creaky door and make a dash for it, hopping stone to stone, slushy snow biting at my feet until—just seconds later, though it feels infinitely longer—I step, relieved, into the first pool.