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You may have noticed people sharing videos of themselves - and others - pouring buckets of ice over themselves recently. Despite what it may look like at first glance it's not just those people's way of dealing with the summer heat; it's a new craze and it's called the Ice Bucket challenge.

But what IS the Ice Bucket challenge? In short, it's people soaking themselves in freezing cold water - usually by pouring a bucket of ice water over their heads - to raise money for charity.

Some people take part in the challenge wearing fancy dress or in public locations, others prefer do it in their swim wear in the garden. But all are aiming to raise as much money as possible.

The craze started in America with the aim of raising money for the Amyotrophic lateral sclerosis ( ALS ) Association.

ALS, also known as Lou Gehrig's disease and Motor Neurone Disease, is a disease that attacks the spinal cord and can lead to speech difficulties, muscle spasms and even paralysis. It affects an estimated 30,000 people in the US and 5,000 in the UK. And it can be fatal.

The bright idea came from former Boston College baseball player Pete Frates, whose career was cut short by ALS after he was widely tipped to be a Boston Red Sox star.

His first challenge was accepted by fellow Boston athletes and some Red Sox players, and since then names such as Justin Timberlake, Mark Zuckerberg and more recently Darren Fletcher of Manchester United have all taken part in the charitable drenching.

The reason it's become such a phenomenon is that, once a person has given themselves a cold shower taking part in the challenge, the wet and freezing victim then nominates someone else to take the challenge.

They can either accept and donate money to the person's chosen charity (originally that was $10 to the ALS Association), or turn the offer down and donate more ($100 to the ALS Association).

The ALS Association reports a significant spike in donations and awareness of the disease as the challenge has taken hold around the world and it's even been trending on Twitter recently.

So far the only well-known figure to decline their challenge has been President Obama – who gave $100 to the charity instead.

Despite coming under criticism for promoting the idea that sub-zero water is a better prospect than giving $100 to charity, the ice bucket trend has raised nearly $3 million for the ALS Association, which they themselves report is a 50% increase on funds from last year.

Here's how it's done:



