Tipping into cold water post-exercise is nothing new – in the 1980s, Sir Alex Ferguson reportedly often sent his Aberdeen players scampering into the North Sea after a game – but the mechanisms at play in improving post-workout recovery have been ambiguous, at best.
Until now. A team of experts from locations ranging from Singapore to Australia has rounded up and analysed the results of 40 years of research examining the potential physiological and psychological benefits of immersing yourself in an ice bath after an intensive training session – and exploring whether it can actually be detrimental.
Let’s start with the basics: as long as you’ve plunged for long enough, cold-water immersion lowers core temperature, a point that will resonate with anyone racing in hotter climes this summer.
“This reduction in temperature is one of the most important reasons for taking a cool dip,” explains one of the authors, Chris Abbiss, associate professor of exercise physiology at Perth’s Edith Cowan University. “It’s associated with numerous local and systemic responses to cold-water immersion (CWI).”
On a basic level, that makes sense. Your body is homeostatic: it tries to maintain a core of around 37°C. Exercising in the heat can cause body temperature to rise to over 38.5°, which is hyperthermia territory; over 40° is life-threatening. Other significant responses include banishing central nervous system (CNS) fatigue, a recent discovery proven by use of MRI scans.
One theory about this focuses on cerebral neurotransmitters in the brain, and the dopaminergic and serotonergic systems that influence mood, sleep and attention. Heat causes these systems to fire and misfire all over the place – and it’s suggested that cooling brings things back to equilibrium. So in the short term – for example, on a double training day – you could train stronger.
“Cold-water immersion also reduces the stress on the cardiovascular system by increasing central blood volume,” says Abbiss. “However, there’s little evidence that it removes muscle metabolites.”
That’s significant, because many athletes take the plunge thinking that flushing through oxygenated blood will clear out the by-products of exercise. This isn’t the case: in fact, “a plethora of studies have observed no change in blood pH” – a sign of metabolic clear-out – and have shown that passive or active recovery is a far more worthwhile exercise. Many triathletes look to cool post-training, whatever the environmental temperature. Don’t. Keep CWI for the heat.
“One final important note is that recent research suggests CWI, while advantageous to aerobic exercise, can be detrimental to strength-training adaptations,” says Abbiss.
So if you’re lifting weights on your next trip to Club La Santa, recover with a light bike rather than an ice bath. Back to Abbiss to prescribe the cooling specifics…
Water temperature of 12-14°C is fine for positive results. It’s tolerable and doesn’t rapidly result in a shivering response, which can eat into glycogen reserves.
The longer the immersion, the greater the effect CWI will have on deep tissue and core temperature. If you get out after 5mins, that’s not long enough to influence recovery. About 20mins would be good.
It has to be a bath with bags of ice, because the temperature of water from the tap is often warmer than 12-14°C. And you can’t get away with a shower, because you need a lot of water against the skin. As well as cooling, this also leads to a hydrostatic effect. The effect of this pressure is similar to the mechanisms by which compression garments are believed to improve recovery (by increasing venous return).