2. Your Heart, Lungs, and Circulation
Aerobic activities
Continuous activity that requires large amounts of oxygen.
Term to Know
The word aerobic means “with oxygen.”
Done regularly, aerobic activity strengthens the heart and the lungs.

3. Your Circulatory System
Consists of the heart, blood, and blood vessels.
Term to Know
To understand how aerobic activities work, you need to have some knowledge of the circulatory system, also called the cardiovascular system.
This system is responsible for circulating blood throughout the body.

4. Your Circulatory System
The heart is the main organ of the circulatory system.
The right side of the heart pumps blood to the lungs, where it picks up oxygen and rids itself of carbon dioxide.
The left side of the heart pumps oxygen-rich blood to the rest of the body.

5. Your Circulatory System
Hemoglobin
An iron-rich compound in the blood that helps carry the oxygen.
Term to Know
The blood carries oxygen via hemoglobin.

6. Your Circulatory System
Stroke volume
The amount of blood pumped per beat of the heart.
Term to Know
When at rest, the heart beats an average of 72 times per minute.
Your heart rate and stroke volume increase during strenuous physical activity.

7. Your Circulatory System
Blood is carried to and from the heart via a network of blood vessels.
There are three types of blood vessels: arteries, capillaries, and veins.

8. Your Circulatory System
Arteries
Vessels that carry the blood from the heart to the major extremities, such as the arms, legs, and head.
Term to Know
Arteries are blood vessels that carry blood to the body tissues.

9. Your Circulatory System
Capillaries
Smaller blood vessels that deliver oxygen and other nutrients to individual cells.
Term to Know
Capillaries are blood vessels that carry blood throughout the body.

10. Your Circulatory System
Veins
Blood vessels that deliver blood back to the heart.
Term to Know
Veins are blood vessels that deliver blood from the capillaries back to the heart via the lungs.

11. Your Circulatory System
Respiratory system
The body system that exchanges gases between your body and the environment.
Term to Know
The oxygen that your blood carries is introduced into your body by means of your respiratory system.

12. Your Circulatory System
The principal organ of your respiratory system is your lungs.
Your lungs exchange oxygen and carbon dioxide through the process of respiration.

13. Your Circulatory System
Diaphragm
A muscle found between the chest cavity and abdomen.
Term to Know
Unlike the heart, the lungs are not a muscle.
Rather, they get their power from the diaphragm, the intercostal muscles around the ribs, and the abdominal muscles in the lower stomach area.

14. Your Circulatory System
Benefits of Aerobic Activity
Strengthens the body
Increases stroke volume
Lowers your resting heart rate
Conditions the muscles used in breathing
Results in more effective delivery of oxygen

15. Your Circulatory System
Cardiorespiratory endurance
The ability of the body to work continuously for extended periods of time.
Term to Know
One long-term result of regular physical activity is cardiorespiratory endurance.

16. Aerobic vs. Anaerobic Physical Activities
There are two sides to total fitness:
cardiorespiratory fitness
anaerobic fitness

17. Aerobic vs. Anaerobic Physical Activities
Anaerobic activity
Activity that requires high levels of energy and is done for only a few seconds or minutes at a high level of intensity.
Term to Know
Aerobic activity must occur over a sustained period of time; anaerobic activity works differently.

18. Aerobic vs. Anaerobic Physical Activities
Anaerobic means “without oxygen.”
The energy produced in anaerobic activities does not depend on oxygen.

19. Aerobic vs. Anaerobic Physical Activities
anaerobic fitness
Higher levels of muscular strength, muscular endurance, and flexibility.
Term to Know
Participation in anaerobic activities leads to anaerobic fitness.

20. Aerobic vs. Anaerobic Physical Activities
Anaerobic activities require large amounts of energy, a requirement that your body cannot meet for very long.
This is because your heart cannot supply enough oxygen-rich blood to your tissues and organs to meet the high demand.

21. Aerobic vs. Anaerobic Physical Activities
When you can meet your energy needs by supplying large amounts of oxygen to your body, you are working primarily in an aerobic mode.
If you cannot meet the oxygen demands of a high-intensity physical activity, your body is more conditioned to working anaerobically.

22. Aerobic vs. Anaerobic Physical Activities
Interval training
A program in which high-intensity physical activities alternate with low-intensity recovery bouts for several minutes at a time.
Term to Know
Interval training can allow you to work aerobically and anaerobically in the same workout.