D4 Force Platforms

Topic

The force platform is a piezoelectric or strain-gauge device that measures—with high temporal and spatial resolution—the three components of the ground reaction force and the center of pressure; this resolution enables the capture of changes in both variables occurring within fractions of a second—details that other measurement methods fail to detect.

The primary measurement provided by the force platform consists of the three components of the ground reaction force: the force the foot exerts against the ground causes the ground to exert, in reaction, a force of equal magnitude and opposite direction upon the body, resolved into forward, lateral, and vertical directions.

In addition to the ground reaction force, the force platform measures the center of pressure—the precise point within the foot's contact area where the ground reaction force is concentrated at any given moment; this center of pressure shifts as the distribution of the ground reaction force changes from one instant to the next.

By measuring the three components of the ground reaction force, the force platform quantifies load distribution: it shows how the force exerted by the body onto the ground is distributed during each phase of movement, revealing whether a specific area of ​​the body is bearing a disproportionate amount of load.

By measuring the center of pressure, the force platform also quantifies stability and balance: the way the center of pressure moves within the contact area—and how far it deviates from a central position—indicates the body's stability while standing or in motion.

With load distribution, stability, and balance quantified, the force platform allows for the diagnosis of three types of abnormalities: gait disorders, where the ground reaction force or center of pressure deviates from expected values ​​during the gait cycle; balance issues, where the center of pressure oscillates more than expected or approaches the edge of the contact area; ...and postural problems, when the distribution of loads between the two feet—or across different areas of the foot—deviates from what is expected in a static posture.

By expressing gait disorders, balance issues, and postural problems in terms of ground reaction force and center of pressure, the force platform converts these three diagnoses into objective physical parameters that can be measured with the same high temporal and spatial resolution during every assessment.

ID:544