In this task, you are given a question and answer for that. The answer will fill in the blank or will complete the unfinished question. Your task is to provide an explanation based on the given question or fill-in-the-blank statement, and answer.

Question: If Jim works hard and decreases the strength of his muscles, his endurance becomes 
 Answer: smaller
Aerobic exercise increases the size and strength of muscles in the heart and helps all your muscles develop greater endurance.