Table 3 Exclusion criterion

Human criteria

- All animal or pendulum-based studies will be discarded.

Intervention criteria

- All studies quantifying other activities than quiet standing (e.g., gait and equivalent, using a moving platform or moving environment for assessment, obstacle dodging, external destabilization, functional reach tests, one leg standing, or any forms of assessment of balance other than standing upright).

- Romberg coefficient (difference between eyes opened and closed) will be accepted as well as standing on foam if there is a comparison with a firm surface.

- Cognitive tasks which do not require to move (e.g., counting or memorizing) will be accepted.

- A standardized posture is not an exclusion criterion but will be noted.

Outcome criteria

- A COP recording is mandatory to not be excluded. All studies than do not compute any parameter to quantify balance through COP data but focus on sway measurement only through sway meter, cumulative balance score (e.g., Sensory Organization Test) or motion capture will be discarded. Studies using Center of Mass (COM) without a COP recording will be discarded too.

Equipment criteria

- There are no equipment criteria as long as the research recorded COP displacement over time. Force platforms, pressure insoles, or any other COP recording systems are all accepted but will be noted.

Population criteria

- All studies including young (< 60 years old), healthy people without a comparison group of older people will be discarded.

- The presence of a neurologic pathology that could influence posture will be an exclusion criterion.

- All studies including recently post-operative participants will be discarded.

Comparison criteria

- All studies than do not compare elderly fallers and non-fallers but focus on methodological issues (e.g., COP features reliability, force platform methodology and validation, biomechanical model validation) will be discarded.