Many people assume that exercise uses energy and therefore causes tiredness. While this may feel true in the short term, regular physical activity actually improves the body's ability to deliver oxygen and nutrients to working muscles.
During movement:
- The lungs take in oxygen.
- The heart pumps oxygen-rich blood throughout the body.
- Blood vessels deliver oxygen and nutrients to muscles.
- Muscles become more efficient at using fuel and oxygen.
Over time, the heart, lungs, blood vessels, and muscles adapt to physical activity. Everyday activities become easier, physical fitness improves, and feelings of fatigue decrease.
People who are inactive often experience the opposite cycle: physical activity feels difficult, they become tired more quickly, and they are less likely to stay active.