The sessions were introduced on a trial basis earlier this year for eight prisoners at the high-security Ringerike prison, home to some of the country's most dangerous criminals, in a bid to help them keep their anger in check. But instead of calming them down, the specialised breathing and meditation involved in yoga served to wind them up, explained the prison director Sigbjörn Hagen.
"The reactions we received from the prisoners who participated in the classes were very varied, ranging from completely positive to completely negative," he wrote in a letter addressed to the group in charge of the yoga project.
On the negative side, Mr Hagen said, learning the ancient Indian routine - designed to harmonise mind, body and spirit - had provoked "strong reactions: agitation, aggression, irritability, trouble sleeping and mental confusion".
Staff at Ringerike say the deep-breathing exercises - an integral part of yoga - made some of the prisoners more dangerous by unblocking their psychological barriers and unleashing otherwise repressed emotions, such as anger, irritation or depression.
The prison has decided to stop the pilot scheme altogether, saying it does not have the resources to provide treatment for increasingly troubled inmates.
The yoga group behind the project professed surprise, insisting that the techniques had been tested on about 100,000 prisoners in 15 countries and had been judged a great success.Reuse content