Why do we train with Kettlebells?  Because of the laws of Physics.

Every body remains in a state of rest or uniform motion unless it is acted upon by an external unbalanced force (Sir Isaac Newton, 1687).
Chances are good that if Sir Isaac Newton were here today, he would choose Kettlebell training over any other training, simply as a matter of physics.
Kettlebells are unbalanced by design, which triggers instability. Every time a body is off balance, muscles have to engage in order to restore that balance. The constant quest for balance and recovery is what requires more muscle use than what is required in a standard exercise routine.
The functional movements of training with Kettlebells not only requires a vast amount of muscles to be engaged at one time, but it also requires the nervous system, cardiovascular system, and skeletal system to work together simultaneously, providing a total body workout experience.
Kettlebells have come a long way over the last 350 years, from being used as functional counterweights in Russian commerce, to being the recognized Soviet National sport, to now being a required training program in today’s United States Secret Service and in the FBI Counter Assault Teams.
With the proper instruction, Kettlebells are the force needed to act upon the body to create the changes people are seeking.