1. Knowledge Base
2. Using the Scan Kit
3. Force Plates & Movement Assessment

# Force Plate Technology

## The article provides a basic introduction to force plate technology.

A force plate is a measuring device (hardware) that has gained tremendous popularity in recent years as improvements in software and computing have allowed them to become much more practical. The technology utilized in force plates themselves is relatively old and relatively simple. Force plates measure the Ground Reaction Forces (GRF) that are generated as an individual stands or moves across them.

The concept of Ground Reaction Forces is based on Newton's Laws of Motion which help to quantify and measure movement based on forces. Specifically, these are the forces that we can measure based on our interaction with the ground because of gravity. A person standing motionless on the ground exerts a contact force on it (equal to the person’s weight) and at the same time, an equal and opposite ground reaction force is exerted by the ground on the person. Similarly, in order to move, we put force into the ground and the ground applies forces back (GRF) onto us which then propels us forward.

In the simplest example, as an individual moves on a force plate, a trace of the vertical GRF is produced across the time of the movement. This trace is called a force-time curve. Instantaneous measures of force and time can be converted to velocity (m/s), power (watts), and displacement(m). Furthermore, these variables can be observed as average or peak values and differentiated based on the eccentric or concentric portion of the movement. The video below shows a great visual of a slow-motion vertical jump synchronized with the vertical force data that can be capture from a force plate; giving us the force-time curve (credit SMU Locomotor Performance Lab).

More advanced force plates can often also measure the three-dimensional components of force relative to the surface area, or put more simply the center of pressure. Balance can be defined as the ability to maintain the center of mass (COM) above the center of pressure (COP) in contact with the ground. Various methods have been used to evaluate balance performance, however, force plate analysis of ground reaction forces representing COP displacement is most common.

Force plates have been utilized for years in the laboratory setting, often in biomechanics programs to quantify gait, balance, and other movements. They are specifically designed to precisely measure ground reaction forces and can be categorized based on several components.

• Sensor Type