The process of balancing muscles that are Hypotonic Muscle or Hypertonic Muscle at the Muscle Response Test (Muscle Response Testing (MRT)).
“Balance” is a state where things are of equal weight or force (Cambridge Dictionnary online). 
When we perform a “balance” we are, using the appropriate stimuli, re-establishing the equal “force” of all the muscles involved: this means that the sum of the vectors of the force of the basal Muscle Tone every muscle involved is 0 and the system is in a balanced state.
Every technique has a “Balance” phase where the appropriate reflex/stimulus is applied in relation to the information gathered in the “Evaluation” phase.