Varying degrees of contractive force in a skeletal muscle are generated through the process of what?

Motor unit recruitment

Explanation:

Motor unit recruitment is referred to as "the successive activation of the same and additional motor units with a higher strength of voluntary muscle contraction." A motor unit is made up of a motor neuron plus the entire muscle fibers it activates.

The central nervous system can raise muscle contraction capabilities through:

-raising the level of active motor units (undergoing spatial recruitment)

-boosting the firing rate/frequency of ecah separate motor units so as to fire in order to optimize the total tension generated (this is known as temporal recruitment)

For every motor unit recruited, 5 Hz is serially summated to the firing frequency of each motor unit action potential (MUAP that is available. The recruitment ratio is estimated from the firing frequency of the quickest firing MUAP divided by the amount of separate MUAPs that is observed on the screen.