Question

which of these is a major difference between skeletal muscle and cardiac (heart) muscle?
cardiac muscle gets tired quickly any time you try to exercise, causing you to stop.
skeletal muscle gets tired fairly quickly, however, cardiac muscle never gets tired.
skeletal muscles are involuntary so they do not require input from your brain to work.
skeletal muscle never gets tired so you can work out for hours and never get tired.

Explanation:

Skeletal muscles are used for voluntary movement and fatigue relatively fast due to their mode of energy - use and recruitment patterns. Cardiac muscle has a continuous blood supply and specialized metabolic properties that allow it to contract rhythmically without fatigue throughout a lifetime. Also, skeletal muscles are voluntary (require brain input), while cardiac muscle is involuntary.

Answer:

B. Skeletal muscle gets tired fairly quickly, however, cardiac muscle never gets tired.