Exploring Locomotion Behavior of Chronic Non-Specific Low Back Pain (cNSLBP) Patients While Walking Through Apertures in Different Configurations: Influence of Environmental and Social Factors.

The critical threshold corresponds to the goal position at which individuals change their mode of action, i.e. the goal at which participants will cross the narrow aperture.

Speed will calculate using the first derivative of the participant's position (location of the center of each participant at each point in time).

The clearance distance corresponds to the distance between the participant and the central obstacle forming the two apertures, i.e. a pole for the condition with modified environment and a human being for the conditions with modified social factors.

The shoulder rotation of each participant will be calculate from the horizontal coordinates of the two glenohumeral (GH) for the unobstructed straight lines and the experimental trials. The angle will be define in the horizontal plane between the GH line and the instantaneous walking direction at time where participants cross the aperture.

The difference between the angles of rotation of the shoulders and pelvis in the horizontal plane of each participant will be calculated from the horizontal coordinates of the displacement of the markers positioned on the two glenohumeral and on the anterior superior iliac spine for the straight-line trials with no obstacles in the path and for the experimental trials.

Pain intensity reflects the overall magnitude of the patient's perceived pain experience. The investigators will assess this variable using a visual analogue scale (VAS) in paper format. The VAS is represented by a 100 mm long horizontal line with descriptors at both ends: on the left "no pain" and on the right "worst pain imaginable". The patient must then draw a mark on the line corresponding to his or her pain experience. "0" corresponds to "no pain" and "10" corresponds to "worst pain imaginable".

Anxiety refers to fear, extreme worrying and hyperarousal symptoms. Depression refers to negative mood, loss of self-confidence, loss of motivation and pleasure. The investigators will use these measures using the Hospital Anxiety Depression Scale (HADS). This tool consists of 14 items scored from 0 to 3. Seven questions relate to anxiety (Total A) and 7 questions to the depressive dimension (Total D), resulting in two scores with a maximum total of 21 each. The higher the score, the more anxiety or depression the person has.

Catastrophizing refers to the cognitive process in which anxious patients dwell on the most negative consequences and refers here to the interpretation of pain as extremely threatening. The investigators will use the Pain Catastrophizing Scale (PCS) to assess three dimensions: rumination, amplification and helplessness. This scale consists of 13 items scored from 0 (not at all) to 4 (all the time) with a maximum score of 52. The higher the score, the greater the level of catastrophisation.

Fear of movement is characterized by pain-related fears and anxieties that often result in avoidance of movement that could cause or worsen an injury. The investigators will use the Tampa Scale Kinesiophobia (TSK). This scale consists of 17 items rated from 1 (strongly disagree) to 4 (strongly agree) with a maximum score of 68. The higher the score, the greater the level of kinesiophobia.

Psychological flexibility measures psychological functioning in phase (in fusion) with the pain or whether the patient has certain degrees of freedom from it. The investigators will use the Psychological Inflexibility in Pain Scale (PIPS) allowing to assess two factors: avoidance and cognitive fusion. This scale consists of 16 items with a scale of 1 (never true) to 7 (always true). The higher the score, the greater the level of psychological inflexibility.

Fear and avoidance beliefs reflect patients' pain avoidance behaviors. The investigators will use the Fear Avoidance Beliefs Questionnaire (FABQ) to assess two subscales: beliefs about work and beliefs about physical activity. The questionnaire consists of 16 items scored from 0 (absolutely disagree with the sentence) to 6 (completely agree with the sentence). The maximum score for beliefs about work is 42 and the maximum score for beliefs about physical activity is 24. The higher the score, the greater the level of beliefs.

Physical functioning refers to the impact on the patient's ability to perform daily physical activities necessary to meet basic needs, ranging from self-care to more complex activities that require a combination of skills. The investigators will use the Roland Morris Disability Questionnaire (RMDQ). This questionnaire has 24 items with a maximum score of 24. The higher the score, the more functional disabilities the person has.

Quality of life refers to the impact on the physical, psychological, and social domains of health, considered as distinct domains that are influenced by a person's experiences, beliefs, expectations, and perceptions. The investigators will use the EuroQol 5 Dimension questionnaire (EQ-5D) allowing for the assessment of five dimensions: mobility, ability to care for oneself, usual work, home, and leisure activities, pain/discomfort, anxiety, and depression. Five degrees of severity in ascending order are used to assess each dimension: "no problems" to "total disability" for items that assess ability, and "no problem" to "extreme" for the other items. The higher the score, the lower the level of quality of life.