1) What is the Principle of Reversibility? 2) What is the Principle of Progressive Overload?

THE PRINCIPLE OF REVERSIBILITY:

The principle of reversibility of light states that light follows the same path if the direction of the travel of light is reversed.

THE PRINCIPLE OF PROGRESSIVE OVERLOAD:

The principle of progressive overload suggests that the continual increase in the total workload during training sessions will stimulate muscle growth and strength gain. This improvement in overall performance will, in turn, allow the athlete to keep increasing the intensity of his/hers training sessions.

exercising at a moderate intensity, and slowly increasing the duration.

psychological stress is stress that happens when a persons mind and emotons respond to stress. an ideal answer for this question woud be increased heart rate.