Bones, tendons, ligaments and cartilage make up the skeletal system. The primary function of the skeletal system is providing support for the body to maintain posture and movement. The skeletal system protects the internal organs such as the brain and heart.

Acupuncture involves the insertion of thin needles into different areas of the body known as acupuncture points. While the practice of acupuncture itself is reported to be thousands of years old, its use in the United States is still relatively new.

Your muscles are strong, tough fibers. However, frequent use, strain and pressure can stretch your muscles too far, resulting in an overuse injury. This injury type is most common in your back and in the muscles in the back of your legs, which are subject to pressure while you exercise.

Think of a bone in your body like a wooden stick -- the larger and denser the stick, the harder it is to break. As you age, however, the hormones that signal your body to build bone start to diminish in production, which can make your bones less dense and more injury-prone.

A disc herniation, defined as a rupture of the outer portion of one or more of your intervertebral discs, is a relatively common health complaint among Americans. Spinal disc herniations, notes MayoClinic.

In our culture, sleep deprivation in the name of accomplishment has become a badge of honor, letting the world know that you are going the extra mile to succeed and provide for your family. But the health repercussions of inadequate sleep may eventually net you diminishing returns.

Bone spurs, or osteophytes, can protrude from the bones of the vertebral column and cause unpleasant symptoms. Others are less problematic.

Bone tissue is constantly being remodeled and repaired by the body. Various disorders can damage bones and result in bone lesions. Symptoms include bone pain or tenderness, and the injury can only be seen using special imaging tests.

A bruised knee can make exercising uncomfortable, but it doesn't have to keep you sidelined. Athletes, dancers and everyday people exercise with a bruised knee. If your doctor has given you the OK to workout, you can still do your cardio and strength-training exercises.

Muscle tone is the amount of tension a specific muscle has, according to the Department of Occupational Therapy at Royal Children’s Hospital. Having low muscle tone will make it difficult to perform an activity or maintain proper posture. Hypotonia is a state in which the strength of the muscle is severely reduced.

You rely on your knees to support your movements during a workout. When you experience pain after exercising, you may be concerned that an underlying condition exists.

Improperly performed situps or doing too many situps before the lower back is sufficiently developed can indeed cause back pain. One common method of the exercise involves placing feet under a bar to make it easier to complete a situp.