Final answer:
Overload, specificity, and progression are the three training principles of the seven principles of training that are fundamental in the construction of PRT program development.
Step-by-step explanation:
The three principles of training that are fundamental in the construction of Physical Readiness Training (PRT) program development are overload, specificity, and progression.
Overload means exposing the body to a greater stress or demand than it is normally accustomed to, which helps improve fitness. Specificity refers to tailoring the training program to meet specific physical goals or needs. Progression involves gradually increasing the intensity, duration, or frequency of the training to continue making improvements.
By applying these three principles, the PRT program can be designed effectively to enhance physical fitness and performance.