Previous SDT research has demonstrated that intrinsic motivation towards treatment is positively associated with adherence to medical regimes among people with chronic illnesses, attendance/involvement in an addiction treatment program, and long-term maintenance of weight loss among morbidly obese patients. Within physical activity research, intrinsic motivation has been found to be strongly associated with physical activity engagement. Similarly, increases in intrinsic motivation from pre- to post- exercise referral scheme significantly predicted greater adherence to the scheme as well as greater sports-related physical activity. The dense body of SDT research in health, including physical activity, suggests that interventions underpinned by SDT, should develop and support intrinsic motivation in order to optimally motivate engagement with PA.