Sheffield city centre was on the move this weekend as more than 100 people took part in a mass fitness class at Barkers Pool.

Shoppers did a double take as crowds gathered outside Sheffield City Hall on Saturday, April 18, at exactly 1pm for a giant fitness class that moved the city.

The Day Sheffield Moved More was organised by leading sport and leisure operator Sheffield International Venues (SIV) through social networking internet sites such as Facebook, Bebo, Twitter and Sheffield Forum.

The flash-mobbing phenomenon involves people meeting in the same location to do something unusual and then dispersing and has seen wacky events taking place at open spaces in major cities across the world.

Organiser Stacey Hartley, E commerce and Marketing Manager at SIV, said: "We wanted to get Sheffield moving like it has never moved before. Other cities have done similar events but wanted to create something unique for local people that everyone could enjoy.

"We set up ‘The Day Sheffield Moved More' group on Facebook and posted it on other social networking internet sites and we were amazed at the response. Everyone who took part had a great time.

"At SIV we are committed to encouraging as many people as possible to take part in physical activity in a variety of ways. It is so important to make exercise and fitness a key part of our lifestyles to maintain good health and this event was just one of the ways that SIV is supporting Sheffield to get on the move."

Sheffield's first ever flash-mob event - 'The Day Sheffield Stood Still' - was held in the Peace Gardens in January.

Flash-mob fans Nicole Deveaux, from Treeton, and Vicky Cloke, from Aston, heard about the event through Facebook.

Nicole said: "It was so much fun and I wish we could do it all over again!

"We love flash-mob events and took part in the last event in Sheffield city centre so we were really excited when we spotted this group on Facebook."

The first flash-mob event was created in Manhattan in 2003, at Macy's department store, when participants converged around an expensive rug.

Watch the action on Facebook (Group Name "The Day that Sheffield MOVED") or Twitter (www.twitter.com/movemoresheff).