Media playback is unsupported on your device

Vikings and yoga with dogs: Fitness programmes put to the test

18 January 2014 Last updated at 11:40 GMT

January is traditionally the month when people decide to get fit.

The Sunday supplements are full of fitness programmes promising to transform your life, and the clothes and equipment to go with it, but the new fad is for extreme fitness.

Newsnight sent super sloth Nimrod Kamer out to look at four of the latest crazes.