With advancements in sports technology, force plates have transitioned from bulky lab equipment to more portable and automated tools accessible to a wide range of users. In this post, we explore the inners workings of force platforms.
A force plate is a equipped with sensors, typically piezoelectric or strain gauges. When force is applied to a piezoelectric crystal, it creates an electric charge that is converted into a voltage signal by a charge amplifier. Whereas, the strain gauge involves capturing changes in electrical resistance due to elastic deformation; force deforms a spring body, altering the resistance of attached strain gauges, which is then converted into a usable voltage signal via a measuring bridge circuit.
Ultimately these sensors measure the ground reaction force (GRF) when an individual stands, walks, jumps, or runs on them.
They work in alignment with Newton's Laws of Motion. According to Newton's Third Law: for every action force, there's an equal and opposite reaction. When standing on a force plate, the vertical GRF reflects the body's weight. As the individual moves, Newton's second law comes into play, stating that force equals mass times acceleration.
How Force Plates Calculate Data
Remember that force plates only directly measure force, but from that raw data other measures can be calculated:
Acceleration-Time Curve: Calculated as force divided by mass (because Force = mass x acceleration).
Velocity-Time Curve: Calculated by integrating acceleration over time, indicating changes in velocity.
Power-Time Curve: Derived by multiplying force and velocity, illustrating power generation during the movement.
From the shape of the force-time curve for various standardised tests, such as a Countermovement Jump (CMJ), different phases of the movement area identified and metrics can be calculated specific to these phases or landmarks.
In this video, we jump inside force platforms to explain how they work using Newton's Laws of Motion. Watch the video below to learn more:
Applications of Force Plates
Now we understand the inner workings of force plates, we can turn our attention to how to use them. Their applications are almost endless, so it can seem overwhelming! As a starting point, I like the following simple system that VALD uses to categorise their ForceDecks tests:
Jumps: CMJ, Abalakov Jump, Single Leg Jump, Squat Jump, Drop Jump, etc.
Functional Tests: Squat Assessment, Push-Up, Sit-to-Stand-to-Sit, etc.
Balance Tests: Quiet Stand, Single Leg Stand, Single Leg Range of Stability, etc.
Isometric Tests: Isometric Mid-Thigh Pull (IMTP), Isometric Squat, Single Leg Isometric Test, Athletic Shoulder (ASH) Test, etc.
Each of these tests can have a variety of applications of their own. For example, CMJs are widely used in sports science for profiling, fatigue monitoring, and rehabilitation and return-to-play purposes.
In our athlete testing series on YouTube, we have highlighted an array of different force plate tests and their applications. These include:
Selecting the most appropriate tests for your setting, whether from the list above or otherwise, depends on the most useful information for your needs. Consider which capacities are most relevant to performance and injury in your population. Positional demands may also create differences within your group; for example, shoulder testing is more pertinent for goalkeepers than outfield players. This is why translating sports science to your specific environment is crucial.
Key Considerations for Utilising Force Plates
Regardless of the tests employed, certain considerations are crucial for accurate data collection and effective use of force plates, including:
Consistency in Data Collection: As much as possible, maintain uniform approaches to testing, testing days in the microcycle and times in the day, and warm-ups.
Setup: Force plates should be placed on a stable, consistent surface to guarantee reliable measurements, especially if they are moved between locations.
Standardised Testing Protocols: Use consistent protocols within testing to ensure repeatability across trials, individuals, and days.
The Future of Force Plates
Force plate technology is widely used across sports and biomechanics laboratories to test athletic capacities, such as force production, power, rate of force development, and strength asymmetries. As technology continues to advance, the potential applications of force plates are set to expand, providing even deeper insights into the mechanics of human movement. However, this technology evolves, maintaining a critical mindset towards the tests employed and consistency towards the data collection approach will also be crucial to get the most from force plate data.
Frequently Asked Questions (FAQs) on Force Plates
What is a force plate?
A force plate is a platform with sensors that measure the ground reaction forces when an individual stands or moves on it. From such force data, acceleration, velocity, and power can be determined, providing valuable data for analysing physical capacities.
What advancements have been made in force plate technology?
Force plate technology has become more portable and the analysis more automated, making it easier to use in various settings and providing more detailed and precise data for analysis.
What types of tests can be performed with force plates?
Force plates can be used for various tests, including jumps (e.g., CMJ, squat jump), functional tests (e.g., squat assessment), balance tests (e.g., single leg stand), and isometric tests (e.g., IMTP, ASH).
What are the benefits of using force plates in sports science?
Force plates provide detailed data on force, velocity, power, and asymmetry, helping quantify athlete capacities, monitor fatigue, assess rehabilitation progress, and manage injury risk through tailored injury prevention programmes.
This article is support by VALD Performance. For more information, about their technology, visit their website.
Stay tuned for more insights on strength testing in our series sponsored by VALD Performance. Subscribe to our blog to stay updated!
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