Movement Performance in Persons With Chronic Back Pain

The goal of this laboratory-based cross-over randomized controlled study is to study the immediate effects Spinal manipulative therapy (SMT) and exercise therapy (ET) compared to open-label placebo (OLP) on movement performance, gait, active trunk mobility and pain-intensity in persons with chronic non-specific back pain. The main question this study aims to answer is: What are the immediate and measurable effects of SMT and ET on work movements, gait, active trunk mobility and pain-intensity in people with chronic non-specific back pain, compared with and in combination with open-label placebo treatment (OP)? The investigators hypothesize that the participants, after SMT and ET, will perform the lifting task faster, and use more range of motion in most of the joints. They also believe that a greater range of motion is used during gait and that the active ROM in the back is increased, while the pain intensity scores decrease after these interventions. The investigators hypothesize that the control intervention (OLP) could be effective as an add-on intervention, but not as a single intervention. All participants will receive all three interventions SMT, ET and OLP and to study the immediate effects, the participants will be asked: * to lift a box with two different weights * to walk straight forward with and without a cognitive dual task * perform two clinical tests of active range of motion ( * rate the intensity of their pain "right now" * rank the treatment effects of these three treatment methods