The principle of progression in endurance training implies that there is an optimal level of overload that should be achieved, as well as an optimal time frame for this overload to occur.1 The Progression Principle instructs that the overload process should not be increased too slowly, or improvement is unlikely to occur.
However, overload that is increased too rapidly can result in injury issues or muscle damage. Thus, exercising above the target zone is counterproductive and can be dangerous and potentially result in injuries.
The Progression Principle states that there is a perfect level of overload in-between a too slow increase and a too rapid increase.
For example, the weekend athlete who exercises vigorously only on weekends, but not regularly during the week, does not exercise often enough to see solid results and so violates the principle of progression. In this situation, the overload process is gone about too slowly.
The Principle of Progression also makes us realize the need for proper rest and recovery. Continual stress on the body and its joints, as well as constant overload, can potentially result in exhaustion and injury. You should not (and cannot) train hard all the time. It is just not physically possible, or wise. Doing so will lead to overtraining and a great deal of physical and psychological damage will result.
What Is Overload?
Overload has been mentioned often throughout this article, as it is a central and key aspect of weight training. Overload means that the intensity with which an exercise is done must be high enough above the individual’s normal range for any desired physiological adaptation (muscle growth) to occur.
Put simply, if you want to see results when lifting weights, you have to lift more weight than your muscles can physically handle at the time.
The only way your body physically changes and grows is if the muscles are taxed to the point where they must grow stronger to lift that weight. When the muscle fibers are taxed in this manner they break, allowing new, and in turn stronger ones, to develop. Thus, the overload process will cause the muscle fibers to grow stronger and, sometimes, bigger in order to handle the additional weight.