Final answer:
The phase that focuses on increasing the load on body tissues is Phase 4 Maximal Strength Training, where exercise intensity is increased for muscle hypertrophy.
Step-by-step explanation:
The phase that focuses on increasing the load placed on the tissues of the body is Phase 4 Maximal Strength Training. This is when the intensity of the exercise must continually be increased to facilitate muscle growth, which is also known as hypertrophy. In this phase, the weights lifted become progressively heavier, challenging the muscles more, which leads to the desired increase in muscle mass. This phase contrasts with endurance training which causes different adaptations such as increased mitochondria and capillary density. However, both resistance and endurance training are essential for developing and maintaining overall musculoskeletal health and function.