Final answer:
Different exercises target different muscle fibers and energy systems, allowing for improvements in both muscular strength and endurance throughout the body.
Step-by-step explanation:
Multiple exercises are needed to improve muscular strength and endurance throughout the body because different types of exercises target different muscle fibers and energy systems. For example, aerobic exercises like cycling and walking increase muscular endurance and cardiovascular health, while anaerobic exercises like weight training increase muscle strength. Resistance exercises specifically target fast-twitch muscle fibers, which are responsible for generating powerful movements. By incorporating a variety of exercises into your workout routine, you can effectively improve both muscular strength and endurance.