Hot, then cold. A guide to contrast therapy

Contrast therapy is the practice of moving between heat and cold: the sauna, then the ice bath, then back again. It is one of the oldest recovery rituals there is, and at Salus House it sits at the heart of the house.

Why we chose Brass Monkey

When we built our recovery space, we wanted the cold to be taken as seriously as the training. Our ice bath comes from Brass Monkey, whose installations run to what they call the Cold Standard: a framework covering the science, the water quality and how each session is dosed. Their science is overseen by Phil Learney, Brass Monkey's Head of Science, who also happens to train with us. You can follow Phil on Instagram at @theptcoach.

What happens in the cold

The first thirty seconds are the hardest part. Researchers call it the cold shock response: a sudden gasp, rapid breathing and a jump in heart rate [1]. Cold water also triggers a release of noradrenaline. In one laboratory study, an hour sitting in 14°C water raised noradrenaline by around 530% and dopamine by 250% [2]. You won't be in for anywhere near an hour, but it shows how strongly the body responds to cold.

The encouraging part is how quickly that response settles. In a study from the University of Portsmouth, people who completed six three-minute immersions roughly halved their breathing rate in the first thirty seconds of cold, from 47 to 24 breaths a minute, and their heart rate response dropped too. The effect was still there seven months later [3].

Why heat belongs with it

Contrast therapy pairs the cold with heat. A review of 18 trials found that alternating hot and cold water after hard exercise reduced muscle soreness and strength loss more than resting did, and worked about as well as cold water alone [4]. The authors were clear that the studies were small and the evidence is low quality, so treat it as promising rather than proven.

The sauna has its own body of evidence. A Finnish study followed 2,315 men for around 20 years and found that those who used a sauna four to seven times a week had about half the risk of dying from cardiovascular disease of those who went once a week [5]. That is an association, not proof that the sauna caused it, but it is a striking one.

Researchers in Copenhagen have also studied winter swimmers who regularly alternate cold water with sauna. Their bodies handled cold differently, producing more heat when cooled than people who didn't [6]. It was a small study of young men, but it suggests the body adapts to both extremes.