Force plates are tools used for the measurement of ground reaction forces during walking, jumping, or any other type of movement. Force plates use a one of several different types of sensors (load cells) to measure forces, and the corresponding values are typically presented in Newtons (N)—the standard measure across physics. Beyond vertical force, some force plates can measure shear forces—i.e. lateral and horizontal forces. These come into play more specifically for healthcare and research applications, such as orthotic bracing and studies of specific neuro-muscular diseases. Force plates measure ground reaction forces. If we know the frequency of the force-data, we can then perform additional measurements that provide us with far more information about human movement. With some basic math we can use this information to measure a whole range of things, including velocity (m/s), power (watts), displacement (meters), temporal parameters (seconds) and left/right asymmetry for bilateral systems.

Postural studies typically consider a number of mechanical variables that can be measured using a force platform, a common tool that allows measurement of the forces and moments of force acting on the body. One of the most commonly used variables in postural studies is coordinate of the center of pressure (COP). The COP is the point of application of the resultant vertical force acting on the body from the supporting surface. Shifting the COP leads to changes in the moment of force acting on the body. COP shifts, therefore, may be viewed as the means of moving the COM, which has to follow the COP since the body can be in an equilibrium only when the projection of the COM on the support surface and the COP position coincide. Controlling COP by changing the activity of postural muscles is commonly viewed as a major mechanism that allows us to keep the COM projection within a safe area. COP coordinates can be computed if the moment of force acting on the body and the two forces that contribute to this moment of force are known. These force and moment components are measured by a typical force platform, as shown in below figure.

What is a force plate