You know fitness when you see it — a strong body, thin and thriving. You see someone who bounds up the stairs, who stretches easily without straining or grasping his lower back, and you consider him fit. You watch a woman dance without having to catch her breath or sit down, and you believe she is fit. You see a man play football with his son and think “fit.”

Fitness sometimes seems like a gift — you either have it or you don't. But in reality, fitness is something you create. To become fit and create a fit life, you need to know what healthy traits and habits compose fitness and how you can go about improving your levels of them. Once you know those things — and once you make their practice a regular part of your life — you will be fit. Fitness is composed of cardiorespiratory health, muscle strength and endurance, and flexibility.

Cardiorespiratory Health

The heart is a muscle that pumps blood through the body via the vascular system, which is composed of your veins and arteries. Meanwhile, your lungs extract oxygen from the air you breathe and send it into the blood for distribution throughout the body.

Heart and lung health, or cardiorespiratory health, means your heart, lungs, and vascular system work together to efficiently process and transport oxygen to your muscles. When your heart is strong, it easily pumps more blood throughout your body. When your heart is weak, it takes more work for it to provide your body with fresh blood and oxygen. If your heart and lungs aren't strong, then even light physical activity, such as carrying a bag of groceries from the car to the house, or walking a little faster around the block, can leave you out of breath.

Muscle Strength and Endurance

Muscle strength means how much weight a muscle can lift, while muscle endurance means how long a muscle can work lifting various weight amounts. Strength is relative. For example, if a twenty-five-year-old man can't lift his five-year-old daughter, he would be considered weak. If his seventy-year-old grandmother can lift the five-year-old, then she's doing pretty well, strength-wise.

Strong muscles are able to lift a very heavy weight once or twice, and a moderate weight more often or for longer periods of time. Putting grocery bags in your car and carrying them to your house illustrate muscle strength and muscle endurance. Let's say you have two heavy grocery bags, and you can lift them from your shopping cart and put them into your car. That's strength. And even if the bags are moderately heavy, you can probably carry them from the trunk of your car parked in your garage to your house fifty feet away. That's muscle endurance.

Flexibility

Flexibility is the ability to move a joint throughout its range of motion. A joint is the place where two or more bones meet; bones are connected by ligaments and tendons, which are connective tissues. Joints allow movement in the body, and flexibility is necessary for efficient movement. Being flexible may also decrease the chance of sustaining muscular injury, soreness, and pain. In other words, when a person lacks flexibility, movement can be limiting, painful, and disabling. Flexibility is essential to your health and a valuable component of your exercise program.

Flexibility exercises are those that gently stretch muscles, tendons, and ligaments to keep them pliable and mobile. Flexibility exercises include stretching, ballet, yoga, and tai chi. When you are fit and flexible, your body is able to do more with less effort, and that feels great and encourages more activity.