Optimum training stress is the goal in order to stimulate a positive adaptive response to training. Training is cumulative and synergistic. It is an accumulation of the demands placed on all systems of the body muscular, metabolic, nervous, and endocrine/hormonal. It is also adaptation to the synergistic effect of work demands on all the biomotor qualities. They are all interdependent. There is a tendency to try to isolate a biomotor quality and try to train a quality to the maximum without consideration of the effect on the whole system. This also has a negative effect on the other biomotor qualities.
Understanding and utilizing the concept of stimulus threshold should help to better direct training by seeking the optimum load necessary to stimulate adaptation. Stimulus Threshold refers to the minimum stress necessary to force adaptation. The key is finding the proper stimulus threshold for each quality being trained in order to take into account the cumulative and synergistic training effect. Some careful planning is necessary but using this concept will ensure long-term progress and minimize the risk of injury and overtraining.