The latest in the Herald's new weekly series on sports science - the good, the bad and the questionable. We will put the science to the test and separate the hard facts from the mumbo jumbo of a multi-million-dollar industry.

Cold Water Immersion (aka Ice Baths)

What is it?

The dreaded ice bath. If you're a professional athlete who plays a contact sport, chances are you've been plunged into a freezing bath water after just about every game or heavy training session you've ever done. The idea is to cut down recovery time with what can only be described as a shock therapy.

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Read also: Sports science myths exposed
The theory: Cold has long been assumed to be the athlete's friend. It's supposed to decrease swelling and inflammation, reduce fatigue and provide general pain relief. Ice baths, in particular, are believed to help recovery by shifting lactic acid out of the muscle bed. However accepted theory on the effectiveness of cold as a treatment appears to be shifting. Dr Gabe Mirkin, the man who pioneered the RICE (Rest, Ice, Compression and Immobilise) injury treatment doctrine that has been standard practice since the late 1970s recanted his work nine months ago. Mirkin published this article in June 2014 suggesting ice and total rest in fact delay the healing process.

The science: There has been a bunch of studies into the effectiveness of CWI and few seem to agree on its effectiveness. Some suggest there are positive results in terms of athletes reporting less soreness and fatigue, however tests that measure athletic performance have been unable to detect any effect.

A 2009 review of existing literature concluded there was little evidence to suggest CWI helped flush muscle lactics or altered physiological markers of fatigue, but that it did have an effect on helping the nervous system recover after heavy workouts. Exactly how the part of the affected nervous system - the bit that controls cardiac parasympathetic activity (for the real geeks out there) - affects athletic performance is not know. A bunch of cyclists who showed improved cardiac parasympathetic activity following ice baths failed to improve their 1km times, while a group of swimmers who were also tested actually returned slower 100m times.

The manufacturers: "Winning is cool' is the rather catchy slogan of hi-tech American ice bath equipment company Coldtub. "Like any type of therapy, detail is key," the company's website says. "Precise temperature control is essential." The comoany manufactures equipment for professional sport teams, universities, serious athletes and the US military. As well a vast range of ice tubs, the company makes underwater bikes, elipitcal trainers and treadmills.

The experts: If you do it right, CWI can be effective, says John Cronin, the director of the Sports Performance Research Institute New Zealand (SPRINZ) at AUT University.

"There is pretty good evidence out there suggesting changes in cardiac responses, peripheral resistance, blood flow and that if you actually toy with the temperature and hydrostatic pressure it's good," says Cronin.

Hydrostatic pressure is the pressure exerted by water due to the force of gravity. The pressure increases in proportion to the depth due to the increasing weight of the water.
Cronin believes the technique can aid recovery - but the question is how much? Does it do more than, say, going for alight jog?

"There is a lot of uptake in cold water immersion but, again, over and above other types of strategies?" asks Cronin.

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Warriors head of athletic performance Balin Cupples admits there is "no exact science" in CWI. "Ice baths reduce the soreness and that perception of fatigue," he says. The club uses them regularly and has recently upgraded its equipment.

The athletes: Warriors and Kiwis captain Simon Mannering believes ice baths are an effective recovery tool and therefore a necessary evil. "I'd be filthy after my career if it emerged that ice baths were a waste of time," says Mannering. "I hate getting in them after a game, especially on a cold night. But I think it's good for me. If it comes out that they are shite I will be filthy."

Mannering's former team mate for club and country Jerome Ropati has no doubt ice baths are effective. "You could be sore for days after a game but an ice bath could cut that down to a day," says Ropati. "I'd certainly stand by it. I've had days where I've haven't had an ice bath and I have been sore for a while. I'm feeling good in the head and good in the lungs but the legs just can't go."