Enzymes are specialized proteins your body uses to carry out a wide variety of chemical reactions. Without enzymes, these reactions would not occur fast enough to sustain human life.

If you have a knee injury, staying in shape without making the knee worse is a major concern. Cardiovascular exercise is important for general health and also aids in healing injuries by providing freshly oxygenated blood cells to the area.

Your muscles need a day of rest in order to recover from a strength training workout, so if you are going to the gym every day, you may want to split up your workout routine into groups that you can work together.

A burning sensation in your feet during exercise can be so uncomfortable that your workout is cut short. The tingling, burning and sweaty feeling makes exercise less enjoyable.

When the knee gets hot after exercising, it could indicate a variety of problems. The increased temperature is often a sign of inflammation -- the body's response to tissue injury or infection.

Kicking a football -- either a round soccer ball, oval American or rugby ball -- uses a lot of muscles and joints. A successful kick requires good eye-foot coordination, balance, accuracy, skill and power.

While your weight can be a reflection of your current state of health, your height usually isn't. According to "Scientific American," 20 to 40 percent of your height is determined by environmental factors like nutrition, but 60 to 80 percent is determined by genetics.

Red, blotchy facial skin is unsightly and can be uncomfortable, depending on the cause of the blotches. When blotches suddenly appear on your face, an allergic reaction or skin condition may be to blame. Your doctor can prescribe an appropriate treatment to clear up red skin blotches and ease any accompanying itching.

If you feel bloated and gassy regularly, you’re not alone -- 10 to 20 percent of adults complain of gas in the form of belching or flatulence, and it’s normal to emit flatus 12 to 25 per times day, according to Brigham and Women’s Hospital.

From single-celled organisms such as bacteria to humans, cells are the basic structural and functional units of life. An adult human body consists of more than 37 trillion cells, according to an estimate published in the November-December 2013 issue of the "Annals of Human Biology."

Waist-to-chest ratio is an important number used to gauge health and fitness. Specifically, it is a measure of the proportion of the waist circumference to the chest circumference. This ratio is used in conjunction with waist-to-hip ratio and body mass index to determine overall body shape.

The process by which dietary calories are absorbed is called metabolism. Metabolism starts with digestion. Digestion begins in the mouth where food is combined with saliva during chewing and carbohydrates begin to break down into simple sugars.