Surely an ice-cold shower is the best way to cool off and drift away quicker? “If you’re trying to go to sleep, the last thing you want to do is go into a freezing cold shower,” he says. The shock of cold water immersion causes the body to produce adrenaline and cortisol, stress hormones designed to keep us alert. “The best way to get heat out of the body then is by immersing somebody in very cold water,” he says. The ideal temperature varies between people but is likely in the mid to high 20C range, whereas a freezing cold shower would be below 10C.