Why Your Heart Never Gets Tired But Your Legs Do

This short explanation covers how the heart and skeletal muscles produce energy differently, why leg muscles fatigue during exercise, and how the heart avoids the same outcome. It also points out a key limitation of the heart's design and what happens when its oxygen supply is interrupted.

■ Why Muscles Fatigue
- Oxygen depletion in leg muscles during exertion
- A less efficient backup energy pathway and its effects
■ Why the Heart Resists Fatigue
- Energy-producing structures inside heart cells
- Constant blood supply and a built-in electrical pacemaker
- Lifetime number of heartbeats
■ The Design Trade-off
- Recovery capacity of skeletal muscles after rest
- What happens when the heart's blood supply is cut off

Viewers interested in basic human physiology, exercise, or cardiovascular health will come away with a clearer picture of how the body manages energy and fatigue. The contrast between muscle types is also a useful reference point for understanding everyday sensations during physical activity.