South Korean experts have said that a vigorous gym exercise session caused a high-rise building in Seoul to shake for 10 minutes earlier this month, prompting hundreds to flee it in panic.

The scenario was re-created in front of journalists on 5 July when a group of 17 middle-aged people working out to a pop song - 'The Power' by German group Snap - caused the building to shake in a similar way.

The group had been doing Tae Bo - an exercise routine combining boxing and martial arts - in the 12th floor gym of the 39-storey TechnoMart mall building.

'Participants in Tuesday's test said they felt the building rolling greatly while others said they had felt lesser oscillations,' TechnoMart spokesman Andy Yang told AFP.

Professor Chung Lan of Danguk University in Yongin city, who led the experiment, linked the incident to a physics principle governing the vibration of a structure when it is matched by another source.

He told a radio programme the building, which is constructed from iron girders and cement, had a characteristic vibration frequency which was 'in phase' with the synchronised movements of the Tae Bo practitioners.

After the first occasion the Gwangjin district government closed the mall, but reopened it after experts said it was structurally sound.

Cho Byung-Joon, an official with the district government, said that depending on the test results officials might immediately allow the fitness club to reopen.

'But practising Tae Bo in that particular building may have to be banned,' Cho said.


http://www.rte.ie/news/2011/0719/korea_exercise.html