Final answer:
Ian's fitness routine suggests that he is applying the principle of overload by progressively increasing the intensity of his exercises to increase muscle strength. The correct option is B.
Step-by-step explanation:
Based on Ian's workout log, the best statement to describe his fitness routine is that He is applying the principle of overload to increase strength. Ian's routine shows that he is gradually increasing the number of exercises like pull-ups, push-ups, and squats he does.
This indicates that he is trying to progressively overload his muscles to improve his strength. The principle of overload involves increasing the demands on the body to make gains in muscle strength, endurance, and size. This is evident from the fact that he does one more pull-up, two more push-ups, and five more squats than the last time he performed these exercises.