How the Stretch Shortening Cycle works:
🏋🏽‍♂️ If we squat down and pause before jumping (static jump) the pause essentially eliminates the stored energy so we have to rely just on contracting our muscles.
This can be helpful though for specifically training concentric muscle force.
🏃🏽‍♂️ Track and field athletes often do pin squats or paused box squats for this effect.
For a vertical jump with a countermovement (stretch) we start to utilize the Stretch Shortening Cycle more.
📊 The muscles stretch on the way down and contract on the way up.
Now we have active muscle force + some extra force from the neuromuscular system (stretch shortening cycle)
📈 The more momentum we have in the countermovement the more we can stimulate the SSC to a point.
We have to be progressive with training because too high of a depth jump for example can lead to too long of ground contact time and less effective SSC.