Inmates at a small prison in Brazil are being encouraged to work towards shortening their sentences by pedalling on exercise bikes.
The pedal power generated by the prisoners in the state of Minas Gerais is then harnessed and turned into electricity, which can be used to power street lights.
By pedalling, the inmates charge a battery which is able to power ten street lamps along the town's riverside promenade.
For every three eight-hour days they spend on the bikes, the participants get one day knocked off their sentences.
It is one of several new projects being implemented across Brazil, all aimed at thinning out the country's notoriously overcrowded prisons.
The inmates say it has helped to restore their sense of self-worth, because they feel that they are giving something back to the outside world.