Joseph Pilates devised Contrology as a complete system of exercises using a range of equipment as well as the matwork programme. Central to his system is the Pilates reformer. This piece of apparatus is comprised of a sliding carriage held under spring tension. A diverse range of exercises can be performed on the reformer, many of which relate to ones that matwork students will be familiar with. The usage of spring tension means that exercises can be performed in a 'closed chain', which gives extra feedback to the body, making it easier to improve quality of movement. The set up of the reformer can be modified according to the needs of the user, for example adding or removing springs will change the resistance which can add challenge or assistance to help you achieve the movement that you want.