Force Plates and Their Role in Sports Performance
A force plate is a valuable tool used in sports science and rehabilitation to measure the forces athletes generate during movement. It helps coaches, trainers, and clinicians understand how athletes produce power, maintain balance, and perform complex motions. By analyzing this data, experts can improve training strategies and reduce injury risks.
"Understanding force plate data goes beyond just measuring strength—it helps coaches, trainers, and clinicians uncover the mechanics behind movement, optimize performance, and reduce injury risk,” shares Dr. Kiara Barrett, Lead Computational Biomechanist at Bertec. “By analyzing key metrics like ground reaction force, rate of force development, and impulse, we gain a clearer picture of how athletes generate power and control their movements."
But what exactly do force plates measure in sports, and why are these measurements important? Let's explore some key force metrics that provide insights into athletic performance and injury prevention.
Peak Ground Reaction Force (GRF)
Peak force is the highest amount of force an athlete generates during movement. It shows how much power an athlete can produce in activities like running, jumping, or cutting. GRF can be measured in different directions:
Forward-backward (anteroposterior) – affects sprinting and stopping ability.
Side-to-side (mediolateral) – helps assess balance and movement control.
Vertical (superior/inferior) – critical to jump performance
Both positive and negative peaks are important, as the polarity corresponds to the direction of the force. For example, in sprinting, a high forward (positive anteroposterior) GRF means an athlete is pushing off the ground effectively. In contrast, a high medial (negative mediolateral) force at the knee during walking, which could lead to osteoarthritis [1]. Identifying these patterns allows trainers to adjust training plans to improve efficiency and safety.
Average GRF
While peak force shows maximum output, average GRF reveals the total force an athlete applies throughout an entire movement. This is calculated as
This metric is useful for understanding the overall load an athlete experiences.
For example, in sports involving repetitive movements like running or jumping, a consistently high average GRF may indicate excessive strain on the joints. By monitoring this metric over time, coaches can modify training intensity to prevent overuse injuries and enhance performance.
Rate of Force Development (RFD)
RFD measures how quickly an athlete can generate force over a specific period of time. The faster the force is applied, the more explosive the movement. This is especially important in sports that require rapid power production, such as sprinting, jumping, and weightlifting.
RFD is calculated as
where GRF final is the GRF at the end of the selected period, GRF initial is the GRF at the start of the selected period, and ∆time is the amount of time in between those two points.
For example:
In volleyball, higher RFD leads to higher vertical jumps [2].
In golf, it translates to faster clubhead speed [3].
By improving RFD, athletes can enhance their ability to produce power quickly, leading to better performance and reduced injury risk.
Impulse
Impulse refers to the total force applied over time, calculated as
Impulse = ΣGRF⋅time Impulse = ΣGRF⋅time
. If you look at a graph of GRF over a movement, impulse is represented by the area under this curve. It plays a crucial role in movements that require power and control, such as jumping or throwing.
For instance:
In baseball, a batter’s follow-through increases the impulse imparted onto the ball, helping the ball travel farther.
In discus throwing, a longer spin before release maximizes impulse, leading to a greater throw distance.
In jumping, greater impulse during push-off results in higher jumps. Understanding impulse helps trainers optimize techniques for power-based movements.
Reactive Strength Index (RSI)
RSI measures an athlete’s explosiveness by comparing jump height to ground contact time. It is commonly used in plyometric exercises like drop jumps.
Why These Metrics Matter
Force plate data helps coaches and clinicians gain deeper insights into an athlete’s capabilities, movement efficiency, and injury risks. By analyzing key metrics like GRF, RFD, impulse, and RSI, they can:
Identify weaknesses and imbalances.
Adjust training programs to maximize performance.
Monitor fatigue and prevent overtraining.
Using force plates as part of an athlete's training routine ensures a scientific approach to performance enhancement and injury prevention. By leveraging these insights, athletes can reach their full potential while staying healthy and strong.
If you want to understand how force plates can be used for your team, connect with us to learn more.
References
[1] Meireles, S., Wesseling, M., Smith, C. R., Thelen, D. G., Verschueren, S., & Jonkers, I. (2017). Medial knee loading is altered in subjects with early osteoarthritis during gait but not during step-up-and-over task. PLOS ONE, 12(11), e0187583.
[2] Majstorović, N. J., Dopsaj, M. J., Grbić, V. M., Savić, Z. S., Vićentijević, A. R., & Nešić, G. P. (2021). Relationship between isometric strength parameters and specific volleyball performance tests: Multidimensional modelling approach. Isokinetics & Exercise Science, 29(1), 83–93.
[3] Johansen, M. J., Aagaard, P., Gejl, K. D., Kvorning, T., & Bojsen-Møller, J. (2023). Influence of muscle strength, power, and rapid force capacity on maximal club head speed in male national level golfers. Journal of Sports Sciences, 41(9), 912–924.
[4] Young, W. B., Miller, I. R., & Talpey, S. W. (2015). Physical Qualities Predict Change-of-Direction Speed but Not Defensive Agility in Australian Rules Football. The Journal of Strength & Conditioning Research, 29(1), 206.
[5] Cormack, S. J., Newton, R. U., McGuigan, M. R., & Doyle, T. L. A. (2008). Reliability of Measures Obtained During Single and Repeated Countermovement Jumps. International Journal of Sports Physiology and Performance, 3(2), 131–144.
