1. More Than 600 Muscles
The same elastic-type material makes up all your muscles. Thousands of fibers mesh together to form this elastic material that creates muscles. You muscles move both voluntarily, like when you move your triceps or biceps to control your arms, or involuntarily like your heart, which beats without you telling it to. Each muscle works to convert energy into motion. There are 640 named muscles in the skeletal muscle group alone.
2. Contractions Move Muscles
Muscles contract in two basic ways. In twitch contractions, the muscle contracts in a short, single move, while tetanus contractions are long and sustained. Thick and thin sections of filaments create contractions. For example, when you want to move your arm, the thick section, called myosin, grabs onto thin filaments, called actin. The movement synchronizes across the entire muscle so that all myosin move together. Isotonic contractions occur when the muscle changes length to exert force. In an isometric contraction, the muscle remains the same length but contracts to help carry a load like a heavy briefcase.
3. Get Smokin' Guns
When most people think of muscles, they think about skeletal muscles, which attach to the skeletal frame of the body. Skeletal muscles develop and bulk out in response to lifting weights. Skeletal muscles work in pairs, with one side moving the muscle one direction and the other side moving it back. Several major muscle groups, like the ones in the legs and arms, have two of each muscle, one per side. Well-toned arms, often referred to as guns or cannons, develop by exerting increasing amounts of force to move weights.
4. Muscles Form the Digestive System
Smooth muscle regulates blood flow, moves food through the digestive tract and regulates air in the lungs. These muscles line the hollow areas of the body and normally contract involuntarily, but you can control some smooth muscle like the diaphragm. Smooth muscle contracts more slowly than skeletal muscle and sustains the contraction longer. The female reproductive system consists of smooth muscle, which creates labor contractions.
5. Your Heart Is the Biggest Muscle
Cardiac muscle refers to the heart, and it's the only one of its kind. Strong, interlocking branches of fibers allow the heart to contract with enough force to pump blood through the body without tearing the fibers. The heart uses twitch contractions only and is incapable of tetanus contractions. The cardiac muscle consistently endures the work required to make the body function.
