Final answer:
Specificity is the principle that states placing increasing amounts of stress on the body causes adaptations that improve fitness.
Step-by-step explanation:
The statement is true. Specificity is the principle that states placing increasing amounts of stress on the body causes adaptations that improve fitness. This means that when the body is subjected to specific types of stress, such as regular exercise, it will adapt and become more fit to handle that specific type of stress. For example, individuals who regularly run will experience adaptations in their cardiovascular system, such as an increase in heart strength and lung capacity, which will improve their fitness.