Physical fitness includes having a strong heart, powerful muscles, balance and agility, muscular endurance and speed and quickness. To improve your fitness in these areas, you'll need to create different workouts by varying the intensities at which you perform your exercises, such as using more resistance to build strength, and working at higher speeds for short durations to build speed. For many people, basic fitness includes your ability to perform physical activity with a sound cardio, strength and endurance base.
Strength refers to the ability of your muscles to perform work at one time, such as lifting a heavy barbell. You build strength by putting enough resistance against your muscles that you cause damage to them. When your muscles repair themselves in response to this damage, they grow bigger. Since your heart and lungs are muscles, some people refer to your cardio capacity as cardio strength.
People who are physically fit are also healthier, are able to maintain their most optimum weight, and are also not prone to cardiac and other health problems. In order to maintain a relaxed state of mind, a person should be physically active. A person who is fit both physically and mentally is strong enough to face the ups and downs of life, and is not affected by drastic changes if they take place.