Inclusion criteria for group 1 (persons with chronic low back pain)  Primary complaint: non-specific chronic low back pain.  Low back pain is defined as pain in the area between the lower ribs and the upper buttock crease, with or without radiation in the leg Chronic: current episode > 12 weeks, mean pain intensity between 3-8/10 Non-specific: the main pain cannot be traced back to a known pathology Age: 18-65 years Acute pain intensity at the time of testing between 3-8/10 (i.e. a pain intensity within this range is necessary to obtain a correct estimate of the pain response) Understanding of the Dutch language (written and spoken)  Inclusion criteria for group 2 (healthy persons)  No acute or chronic musculoskeletal complaints (i.e. VAS> 2/10 in the last 24 hours) Age: 18-65 years Understanding of the Dutch language (written and spoken)  Exclusion criteria for both group 1 and 2  Invasive spinal surgery within the last 18 months (arthrodesis will always be excluded, microsurgery is allowed) Radiculopathy (uni- or bilateral) of the lower extremities Comorbidities: paresis and sensory disturbances with a neurological cause in the lower extremities, diabetes mellitus, rheumatoid arthritis, autoimmune disorders etc. Pregnancy Ongoing compensation complaints and/or incapacity for work > 6 months Previous active rehabilitation (i.e. exercise therapy) for low back pain in the last 6 months.