To manipulate the spine, the chiropractor applies a sudden, controlled amount of force to specific areas of the spine. This technique is not normally painful, but patients may hear popping noises as it is performed, or experience muscle soreness (similar to what they would experience after a workout) following their adjustment.  In certain situations, chiropractors may opt to use spinal mobilization, a less forceful form of spinal manipulation. This method uses fewer thrusts and more stretching, and it might include the use of an activator, a metal tool that applies direct force to a single vertebra.