Originally Posted by MikeM
Hey Daniel! Good to hear from you.
How did you know the height to set your box, and what is the purpose of breaking up eccentric and concentric?
The box can be adjusted according to the goal. I usually have my athletes have a low box day which is 1-2 inches below parallel and a high box day which is 1-2 inches above parallel.
This all depends if you have a gym with the ability to make adjustments easily. Most commercial gyms dont have a box and many end up only using a bench which for the average person is above parallel.
The purpose of breaking up the eccentric and concentric allows the individual to get best of both worlds. During the eccentric phase the muscles lengthen and resist against the load during the descent which causes an increase of energy in the muscle using the stretch reflex.
Now when you sit on the box, it is suggested to pause on the box. This is known as the static phase of the lift, where the muscles are neither lengthening nor shortening. When you pause on the box, energy dissipates into the box causing the individual to then have to concentrically contract the muscles enough and hard enough to stand back up.
This is great to increasing your 'starting strength'. By going from static to dynamic your body recruits more motor units in order to overcome the load. become more efficient of recruiting more motor units during a movement leads to strength improvements.
hope this made sense. my mind always goes all over the place.