So what are some of the variables you might want to keep an eye on in this unloading/unweighting phase?
Remember Newtons Third law of motion – for every action there is an equal and opposite reaction. The body working with gravity or against gravity is what the force plate is picking up and determines the shape of the force-time signal. Also remember the force signal is essentially an acceleration signal multiplied by whatever the mass of the client/athlete is (Newtons Second law Force = mass x acceleration). In essence you are looking at how well the client/athlete accelerates and decelerates their centre of mass (COM) in a CMJ signal i.e., a=F/m (see figure).
So what is the lowest point on the CMJ signal as denoted by the black circle? Do you think getting closer to zero serves any purpose? Can this variable give you insight into an individual’s unloading capability? Do you need other signals/data to really understand unloading?
Have a think and we will explore in the next post on force plates.