The aim of the present study is to quantify the relative contribution of variables obtained during a physical fitness evaluation and a short screening questionnaire in determining the short-term and long term risk of persistent disabling low back pain in patients with chronic low back pain. It has been hypothesized that patients with higher physical fitness will present a lower risk of persistent disabling low back pain and so, a lower score on the questionnaire.

Inclusion Criteria:

• adults between 18 and 60 years old
• nonspecific low back pain : pain located between the twelfth rib and the inferior gluteal fold for which no specific source of pain could be identified
• chronic low back pain : pain present for 12 weeks or more, and included both constant and recurrent patterns of pain
• able to read and understand French

Exclusion Criteria:

• History of surgery or major trauma to the spine
• Current use of medication known to impair physical effort and pain perception
• Lumbar scoliosis of more than 20°
• Collagenosis, severe osteoporosis
• Neuromuscular disease
• Malignant tumor
• Non-controlled hypertension
• Infection
• Radiculopathy
• Progressive neurologic defect
• Myelopathy
• Lumbar disc hernia
• Pregnancy
• Active lower body injury and/or severe and disabling pain limiting the capacity to undergo the evaluation.

volunteer with chronic nonspecific low back pain will be recruited among the university's community, its outpatients' chiropractic clinic and through advertisements in the local newspaper. They will first be screened by clinicians at the outpatients' chiropractic clinic in order to assess for the various inclusion and exclusion criteria.