Most plant and tree species try to recover from bad pruning by sending off sucker growth, multiple stem growth from the lower trunk. You may think that this is a positive sign of new growth development but in reality, it is a sign that the plant or tree is dying.
Air circulation is a big factor in the health of your shrub or tree. To many branches crowding the center will decrease air circulation and cause the center to die. This is most prominent in evergreens (i.e.: cedars, junipers, spruce, pine, etc.). Once the center is dead, the entire plant will soon die as well. Deciduous shrubs will show this display of center-crowding branches when they have been poorly pruned or sheared.