RESUMO
Political decisions about the way that public health initiatives are implemented have a significant impact on the ability to evaluate their effectiveness. However, the influence of the political imperative has been little explored. This case study of key research, policy and practice events concerning one initiative, exercise referral schemes (ERSs), demonstrates that these schemes were encouraged to expand by the Department of Health (DH) before DH-funded evaluations had reported their findings and with little reference to National Institute for Health and Clinical Excellence (NICE) recommendations. Policy evolved in parallel rather than in conjunction with the development of evidence, and experimental evaluations in England are now unlikely. This is due to the comprehensive coverage of schemes, widespread assumptions of effectiveness, likely difficulties in obtaining research funding, indirect adverse consequences of dismantling schemes and lack of appropriate process and outcome data. Embedding a commitment to robust evaluation prior to universal adoption of new initiatives has been shown to be feasible by policy-makers in the international setting. This is required to prevent the establishment of public health interventions that do not work and may cause harm or widen health inequalities.