Which of the following is not an accepted training principle?

The correct answer is the Quality Principle, as it is not an established or widely recognized training principle within the context of exercise science.

The Specific Adaptation to Imposed Demands (SAID) Principle emphasizes that the body will adapt specifically to the types of stressors it is exposed to during training. This means that to improve in a particular physical capacity, such as strength or endurance, the training needs to mimic the demands of that capacity.

The SAID Principle is closely related to the specific adaptation concept and is often cited in discussions of training specificity, which highlights how targeted training protocols lead to more effective performance improvements in desired activities.

The Progressive Overload Principle is another widely accepted training principle, which states that to continue making progress in fitness and performance, one must gradually increase the intensity, duration, frequency, or type of exercise. This principle is critical for promoting adaptations in strength, endurance, and overall fitness levels over time.

In contrast, while "quality" in training can refer to execution and focus on proper technique, it does not stand alone as a formally recognized principle in the literature of exercise science or kinesiology. Thus, it is not considered an accepted training principle like the others mentioned.