The number reps may change for each set of exercises done. When you train for power, you are automatically training for size or mass. The larger the muscle grows, the greater the amount of weight you can lift. Strength is usually a balance between power and endurance, being able to work hard for extended periods of time. Strength training will also provide the best toning and is probably the most economical program.
Endurance is the ability to maintain an exercise over an extended period of time.
Continuous circuit training is a good example of endurance training. With circuit training you do a variety of exercises at a sustained pace in which you are training aerobically. Endurance weight training provides an excellent start off routine. It is also used to periodically rest the body from the rigors of power and strength routines. Muscle fibers can vary between individuals.