Because muscular power is not a necessity when performing daily activities, it is not typically considered a component of good health. For this reason, it is not usually emphasized is general physical fitness and wellness programs. Although many of the movements within Krav Maga can be practiced or learned at a slower pace, once the correct motor patterns have been learned, the techniques are then practiced with powerful and explosive bursts.
The development of power is a necessity within a Krav Maga training program for two primary reasons. The first is to make your punches and kicks as effective as possible. Krav Maga would be doing a disservice to civilians if it touts itself as a practical self-defense system but is not effective in reality.
Secondly, power is needed to prevent injury to oneself. Within the Krav Maga curriculum, students are taught to make their attacks with enough power to do damage to an assailant if needed. Knowing how to generate this power is one thing, but having the ability to withstand the power you generate without injuring yourself is the crucial piece of the equation.
A certain amount of training needs to be done in order to make powerful contact to the bag without straining any of the soft tissues. This goes back to the adaptation principle. You need to progress through exercises slowly so that the connective tissues can become familiar with the type of stresses being placed on them. Performing exercises at high forces and velocities significantly increases the risk for injury. But if you are training in a sport that requires explosive movements with large forces placed on the body, the risk for injury increases even further.
So what do you do? You prepare your body appropriately with correct alignment, technique, and awareness so that when you are playing your sport or doing an activity that may be strenuous on the joints, your body has some ability to withstand the forces placed upon it with less chance of injury.