Some physicians, physiotherapists and nurses use or even suggest unstable shoes in cases of low back pain. No studies on the real effects of these shoes on low back pain in health care professions have been carried out and therefore as yet there is no real evidence of their effectiveness. Thus the investigators assume that wearing unstable shoes over a period of six weeks could reduce low back pain and functional disability due to the changes of the gait and posture and may increase the quality of life.

The purposes of this study are:

1. To evaluate the modifications of pain level, functional capacity and quality of life among individuals with moderate level of non-specific chronic low back pain after wearing unstable shoes.
2. To quantify biomechanical modifications of gait and posture.

Inclusion criteria:

• employees of Geneva University Hospital
• working in a standing position for at least 50% of their working day
• aged between 30 and 65
• having chronic low back pain that has been defined at least 3 out of 10 on a visual analogue scale during the last 3 months or the need to take regular pain medication for this reason

Exclusion criteria:

• having severe pain in other body parts
• undergone back surgery, neurological or balance problems
• inability to walk a distance of 100 meters
• already worn unstable shoes and being off of work because of low back pain