X: Ozone layer destruction
Y: Mass extinction
There are 3 fitness principles: overload, progression and specificity.
According the principle of overload in order to improve, athletes must continually work harder as they their bodies adjust to existing workouts. This <span>is the basic sports fitness training concept.</span>
In the 3-week workout routine that incorporates the fitness principle of overload several things must be satisfied:loads should be gradually and progressively increased , the training loads should be planed and monitored, the workout routine should include workouts that allow recovery (stretching for example), competition should be involved, and very important muscular failure should be avoided.
