How are muscular endurance and muscular strength related?

Muscular endurance is determined by how well your slow twitch muscle fibers are developed.

In case your wondering what slow twitch muscle fibers are: there are generally two types of muscle fibers in your body, slow twitch and fast twitch. Slow twitch muscle fibers cannot exert as much force as fast twitch, but can sustain an effort over a much greater period of time. Fast twitch muscle fibers can exert a great amount of force but for a very limited amount of time. Therefore, slow twitch equals endurance, while fast twitch equals strength.

If you are looking to improve muscular endurance, the best way would be to involve yourself in just about any cardivascular activity, running, biking, and playing sports.

If you are looking to improve the endurance of your upper body, bodyweight exercises such as chin-ups, push-ups, triceps dips, etc., will improve this, and your strength as well.