Muscles are a bundle of long slender cells (muscle fibers) that have the power to contract and produce movement. They also perform vital body functions, protect the contents of the abdomen against injury and help support the body.
What types of muscles are found in the human body?
The human body has three types of muscle: skeletal, smooth, and cardiac. The following table provides a quick comparison among these muscle types.
|Voluntarily controlled||Involuntarily controlled||Involuntarily controlled|
|Attached to bones||Found on hollow internal organs such as stomach and blood vessels||Found on the heart’s wall|
|Responsible for respiration, posture and locomotion (movement) of the skeleton and muscles and controlling facial tissues||Responsible for the movement of substances such as food and blood||Responsible for pumping blood throughout the body|
Skeletal and cardiac muscles are striated - the most common types of muscle tissue in your body. A striated muscle is a muscle composed of thousands of units known as sarcomeres. Each sarcomere is composed of distinct bands of different material which give the muscle a striped or striated appearance when it is viewed at a high level of magnification under a microscope.
What is a muscle strain?
A muscle strain (also known as pulled muscle) is an injured muscle that has stretched or torn muscle fibers. Most muscle strains typically happen because the muscle has been stretched beyond its limits, it has been forced to contract too strongly or due to inadequate warmup or rest during intensive training.
What muscles are more commonly strained?
Some of the most commonly strained muscles are leg muscles such as the thigh muscles, hamstrings, and calves. Muscle strains to the intercostal muscles (the muscles between your ribs) are also common and can cause chest pain - 21 to 49 percent of all musculoskeletal chest pain. These muscles are usually injured during a twisting motion (like when you hit a baseball, golf ball or tennis ball).
What causes muscle strain?
Sometimes a muscle strain can result from traumatic impact or wrenching of the muscle. Even fatigue can lead to muscle strain. Research indicates that those who suffer from chronic sleep deprivation and fatigue are more likely to also suffer from muscle strains than those who get enough sleep.
How is the severity of a muscle strain classified?
Similar to ligament sprains, muscle strains are classified into three grades, depending on the severity of the muscle fiber damage:
- Grade I - a mild strain that only involves a few muscle fibers being stretched or torn. The injured muscle is tender and painful, but it has normal strength.
- Grade II - a moderate strain that involves a greater number of injured fibers and more severe muscle pain and tenderness. There is also mild swelling, noticeable loss of strength and sometimes a bruise.
- Grade III - a severe strain that involves a completely torn muscle. Sometimes it can cause a "pop" sensation as the muscle rips into two separate pieces or shears away from its tendon. Grade III strains are serious injuries that cause complete loss of muscle function, as well as considerable pain, swelling, tenderness and discoloration. Because Grade III strains usually cause a sharp break in the normal outline of the muscle, there may be an obvious "dent" or "gap" under the skin where the ripped pieces of muscle have come apart.