1. M.J. Díaz-Arribas, MPT, PhD, Physical Medicine and Rehabilitation Department, Faculty of Medicine, Complutense University, Madrid, Spain; and the Spanish Back Pain Research Network.
2. F.M. Kovacs, MD, PhD, Scientific Department, Kovacs Foundation, Paseo de Mallorca 36, E-07012, Palma de Mallorca, Spain; and the Spanish Back Pain Research Network.
3. A. Royuela, PhD, CIBER Epidemiología y Salud Pública (CIBERESP), Madrid, Spain; Unidad de Bioestadística Clínica, Hospital Ramón y Cajal, IRICYS, Madrid, Spain; and the Spanish Back Pain Research Network.
4. M. Fernández-Serrano, MPT, Physical Therapy and Nursery Department, Alcalá University; and Primary Health Care Research Group (INFICAP); and the Spanish Back Pain Research Network.
5. L. Gutiérrez-Fernández, MPT, Primary Health Care Research Group (INFICAP); and the Spanish Back Pain Research Network.
6. O. San Martín-Pariente, MPT, Primary Health Care Research Group (INFICAP); and the Spanish Back Pain Research Network.
7. V. Abraira, PhD, CIBER Epidemiología y Salud Pública (CIBERESP); Unidad de Bioestadística Clínica, Hospital Ramón y Cajal, IRICYS; and the Spanish Back Pain Research Network.
8. M. Ramos-Sánchez, MD, PhD, Physical Medicine and Rehabilitation Department, Faculty of Medicine, Complutense University, Madrid, Spain.
9. R. Llorca-Palomera, MD, PhD, Physical Medicine and Rehabilitation Department, Faculty of Medicine, Complutense University.
10. P. Pardo-Hervás, MD, PhD, Physical Medicine and Rehabilitation Department, Faculty of Medicine, Complutense University.
11. M. Gestoso, MD, Scientific Department, Kovacs Foundation, Palma de Mallorca, Spain.
12. Other members of Primary Health Care Research Group (INFICAP) who authored this study are: G.C. Sánchez-Gil, M.Á. Elena-Lucas, R. Paniagua-de-la-Calle, I. Castellanos-López, M.Á. García-Heredia, A.M. Cerón-Sanz, B. Victoria-González, C. Monsalve-Martín, J.M. Duque-Heras, M.J. Juanes-Hernández, J. Saura-Contí, J.L. Soto-Sáez, C. Román-Moraleda, C. Ruiz-Arias, B. Martín-Mora, R. Escolano-García, J.