Manual therapy includes methods where the therapist's hands are used to stretch, mobilize or manipulate the spinal column, paravertebral structures or extremity joints. The aims of these methods are to relieve pain and improve function. In Norway only specially qualified physiotherapists and chiropractors are authorized to perform manipulation of joints (high velocity thrust techniques). To become a qualified manual therapist in Norway one must have a minimum of two years of clinical practice as physiotherapist followed by two year full time postgraduate training in manual therapy (a total of six years). Historically the Norwegian manual therapy system was developed in the 1950s by physiotherapists and medical doctors in England (James Cyriax and James Mennell) and Norway. As a result doctors allowed physiotherapists to use manipulation as a treatment method of both spinal and peripheral joints. In 1957 the Norwegian health authorities introduced reimbursement for manual therapy performed by physiotherapists.