Force Plate Explained: How It Measures Ground Reaction Force, Center of Pressure and Impulse

Medical and sports equipment has evolved rapidly over the last decade, and the force plate is one of its quiet success stories. Despite its simple, flat appearance, it is a cornerstone technology in biomechanics, and it is also the building block of larger, more complex equipment.

What Is a Force Plate?

A force plate is a metal plate fitted with sensors that detect the forces and moments applied to its surface. It measures the ground reaction force: the force the ground pushes back with when you stand, walk, land or jump. When you stand or perform an action on the plate, it captures the three-dimensional forces (F_x, F_y and F_z) and the moments, or torques, around the centre of the plate. Those moments are what let software work out the center of pressure.

How Does a Force Plate Work?

A force plate works in three stages: mechanical input, transduction and signal processing.

1. Mechanical input

When a force is applied to the surface, it causes tiny mechanical changes in the sensors beneath the plate.

2. Transduction

The sensors convert that mechanical change into an electrical signal. Piezoelectric sensors generate an electric charge proportional to the applied force. Strain gauge sensors change their electrical resistance when they deform. Different force plates use different sensor types.

3. Signal processing

An analog-to-digital (A/D) converter turns the electrical signal into digital data. Software then interprets the data to calculate the magnitude and direction of the forces.

Force Plate Calculations: Force, Center of Pressure and Impulse

Once the raw data is available, three main outputs can be calculated: force, center of pressure (CoP) and impulse.

Total force

The total (resultant) force combines the three force components. Because they act in different directions, they are added as vectors:

In a vertical jump or a stand, F_z (the vertical component) dominates, so it is the main signal analysts study.

Center of pressure (CoP)

The center of pressure is the point where the total resultant force acts. It is calculated from the moments and the vertical force, using the forces measured at the plate’s four corners:

CoP values are essential for assessing postural stability and balance.

Impulse

Impulse comes from the impulse-momentum relationship:

Here J is the impulse, the area under the force-time curve. Integrating the net vertical force (force minus body weight) over time gives the change in momentum. Dividing by body mass gives the change in velocity, which reveals the body’s take-off velocity. Jump height then follows from h = v² / 2g.

Force Plate Applications in Rehabilitation and Sports

These calculations let clinicians measure the rate of force development and jump height, and identify imbalances between the legs after an injury. That gives them objective data to plan rehabilitation, and to judge whether a patient is ready to continue care or to walk and perform tasks independently.

• Rehabilitation: compare left and right leg loading and track recovery with numbers rather than impressions.
• Sports performance: document and analyse jumps and landings to optimise power training.
• Balance and posture: use CoP to assess stability in clinics and labs.
• Ergonomics and research: force plates can be customised for the purpose, from gait labs to student projects.

Force plates pair well with other sensing tools. See how motion is tracked with wearables in our guide to the IMU sensor and Motivus.

Medsby BioMechX: A Force Plate with Open Data

At Medsby we make a force plate called BioMechX (see also BioMechX V4). It works as a force plate and also lets third-party software use its data for analysis. As an example, here is how Python can analyse BioMechX force data.

Analysing jumps with Python

BioMechX connects over Wi-Fi, and its web app shows the raw data. You can download that data and run it through analysis code. The analysis code splits the recording into individual jumps, isolates one jump and shows the forces during it.

Reading the results

The calculations judge the quality of the jump and the forces applied. They give metrics such as peak eccentric and concentric force, and show whether the total force the body can apply meets a healthy threshold. The data below is from one countermovement jump (jump #13).

Live data for games and apps

The force plate can also drive game mechanics using the live data from the web app. That makes BioMechX a versatile tool for clinics, labs, classrooms and interactive projects.

Force Plate Solutions from Coimbatore, Tamil Nadu

Medsby is a biomedical and engineering solutions company based in Coimbatore, Tamil Nadu, working with engineering colleges, researchers, clinics and innovators across India. If you are a physiotherapy clinic, sports science team or biomedical lab in Coimbatore, Chennai, Madurai or anywhere in Tamil Nadu looking for a force plate, our team can help with product guidance, set-up and training. Explore our biomechanics products, academic lab establishments and industrial training programmes.

Frequently Asked Questions

MS

About the author Mithuna Saravanan

Project Engineering Intern, Medsby  |  Bioengineering student, University of Pittsburgh

Mithuna Saravanan is a bioengineering student at the University of Pittsburgh with a strong interest in biomechanics and medical innovation. At Medsby, she is gaining hands-on experience in engineering and healthcare technology, and she is passionate about learning how engineering can improve human health and movement.

G

About the editor G. Guruprasandh

Founder & CEO, Medsby Healthcare & Engineering Solutions

Guruprasandh is the founder of Medsby, a Coimbatore-based manufacturer and technology service provider established in 2014, specializing in wearable technology, healthcare devices, and 3D printing. With over a decade of experience in healthcare technology and engineering, he is committed to knowledge sharing, upskilling, and educational training for students and young innovators.

Keep exploring