Failure. This one little word generally has a negative connotation attached to it, yet in the world of exercise, strength training ‘to (muscle) failure’ is the goal. Training to failure means the trainee loads the muscles through a pain free range of motion to the point of absolute muscular exhaustion, i.e., the inability to move the weight, even another inch, with safe and proper form.
The true, universal value of exercise boils down to only one thing – your quality of life. Our functional ability and stamina depend on our physical strength – the more we have, the more we can do, and the better we will age (and the more fun we will have doing it). Put simply, use it or lose it.