From that record the software calculates your jump height, force, power and the balance between your legs. A coach runs every test. The lab is at 2048 NW 22nd Ct in Allapattah, near Wynwood and Midtown.
What a force plate measures
Each plate measures vertical ground reaction force, the force the ground pushes back with as you push into it. Sampled a thousand times per second, it becomes a force-time curve, a line that shows your force from the moment you start to move until you leave the ground and land. Because there are two plates, the curve is recorded for each leg separately.
In a countermovement jump the curve has clear phases. You dip down, the braking phase slows the dip to a stop, and the propulsive phase drives you up and off the plates. How long each phase takes and how much force you produce in it describe how you jump, so two athletes with the same jump height can show very different curves. An independent study compared Hawkin Dynamics plates with laboratory force plates and found them a valid alternative for countermovement and drop jumps (Badby and colleagues, 2023).
The tests and the numbers
The main test is the countermovement jump: you stand still, dip and jump as high as you can, with several attempts and full rest between them. Depending on the athlete, the coach adds a squat jump, which starts from a held bottom position, and reactive jumps such as the drop jump, where you step off a box and rebound as quickly as you can.
The report includes jump height, peak force, peak power, rate of force development (how fast your force rises), impulse, and the left-right asymmetry index. For reactive jumps it adds ground contact time and the reactive strength index, which divides jump height by contact time. For the countermovement jump we report RSI-modified, which divides jump height by the time it took you to leave the ground.
How the lab uses it
Onyx Performance members do a short jump test on the force plates in the Friday classes. Jump height, rate of force development and the asymmetry index are saved to your account in the Onyx Performance OS app, so each week sits next to the last. A single jump is one input among several. A meta-analysis of countermovement jump monitoring found that the average height of several jumps was more sensitive to fatigue and recovery than the single best jump (Claudino and colleagues, 2017), so we look at both.
If you are not a member, the force-plate tests are part of the Onyx Assessment, a 60-minute visit with a coach that also includes a body composition scan, a movement screen and a conversation about your goals and training history. It costs $149, booked and paid online, and it counts toward your first month of Onyx Protocol or your first Onyx Private package if you join within 14 days. The assessment is designed and overseen by the founder, Alejandro Garcia, CSCS, an adjunct professor of kinesiology at Florida International University and a PhD candidate in exercise physiology at the University of Miami.
Teams, clubs and schools can book a ninety-minute testing day for a whole roster, and the teams page has the inquiry form.
What it does not do
Force plate testing describes how you produce force on the day of the test. It does not diagnose injury, and one number on its own does not tell you your potential. A left-right difference of more than about ten percent in a two-leg jump is worth a closer look and usually earns some single-leg work, and if the difference is new, the coach asks how it got there. If you are in pain or recovering from an injury, a medical professional decides what you are cleared to do, and we test within that.
Who it is for
Athletes who want to know whether their strength work is turning into power, adults who want a measured record of their training, and coaches who want to follow a roster through a season. The guide What your force plate numbers mean explains the four numbers we use most, and the performance testing page lists every test the lab offers.
Sources
- Claudino JG, Cronin J, Mezêncio B, et al. The countermovement jump to monitor neuromuscular status: a meta-analysis. J Sci Med Sport. 2017;20(4):397-402. doi.org/10.1016/j.jsams.2016.08.011
- Badby AJ, Mundy PD, Comfort P, Lake JP, McMahon JJ. The validity of Hawkin Dynamics wireless dual force plates for measuring countermovement jump and drop jump variables. Sensors. 2023;23(10):4820. doi.org/10.3390/s23104820