Force Plates in Sport Science

Force platforms or force plates are instruments that measure the ground reaction forces generated when someone stands or jumps on it, or moves across it. They are used mostly in biomechanical research to quantify balance and gait, and used in sport fitness testing to quantify strength and power profiles. In the sports setting, they are used for monitoring training effectiveness, return to play protocols, and athlete screening.

The force plate is usually comprised of a rectangular metal plate with piezoelectric or strain gauge transducers attached at each corner, which give an electrical output that is proportional to the force on the plate. A commercially available piezoelectric type force plate is made by Kistler.

Force plates usually provide a force-time-curve. As well as vertical forces, some force plates can measure shear forces (e.g. lateral and horizontal forces).

The data provided from the force plate can be used to determine a whole range of other measurements, including:

fitness testing using a force platefoot landing on a force plate

Use of Force Plates in Fitness Testing

Force plates are still usually reserved for use in scientific research. As they become cheaper and more widely available, more tests are being developed (reactive and Dynamic Strength Index), and also they can be used to provide more information on current tests (e.g. vertical jump).

A common use of a force plate is for measuring vertical jump height, though more simple timing mats can do the same thing. Instead of just placing a mark on the wall, jump height can be more accurately measured using lasers or timing mats, and extra information about the force/velocity curve can be gained by jumping from a force plate.

You can calculate vertical jump height using various measures from a force platform. The vertical jump height in meters can be calculated from the time (in seconds) using this formula: jump height = 4.9 x (0.5 x Time)2. It can also be calculated by applying the impulse–momentum theorem to the force–time curve, and by applying the work–energy theorem to the force-displacement curve. Ground contact time is the time between the first foot contact with the force platform and when the subject's feet left the mat.

Example Products

The Kistler Force plate is a research platform linked to a video camera that provides information about forces passing through foot joints and the foot in all three planes of space.

Fitness Tests Using Force Plates

Fitness Tests Using Timing Mats

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