How is muscle formed

Impulses from nerve cells control the contraction of each muscle fiber. To fuel a muscle, the body makes adenosine triphosphate ATP , which muscle cells turn into mechanical energy. Humans and other vertebrates have three types of muscle: skeletal, smooth, and cardiac.

Skeletal muscles move the external parts of the body and the limbs. They cover the bones and give the body its shape. As skeletal muscles only pull in one direction, they work in pairs.

When one muscle in the pair contracts, the other expands, and this facilitates movement. The muscles attach to strong tendons, which either attach to or directly connect with the bones. The tendons extend over the joints, and this helps keep the joints stable. A person in good health can consciously control their skeletal muscles.

Most visible body movements — such as running, walking, talking, and moving the eyes, head, limbs, or digits — occur when the skeletal muscles contract. Skeletal muscles also control all facial expressions, including smiles, frowns, and mouth and tongue movements.

Together with the tendons, they keep the bones in the right position so that the joints do not dislocate. Skeletal muscles also generate heat when they contract and release, and this helps maintain body temperature. The two main types of skeletal muscle are slow-twitch and fast-twitch. These are dense and rich in myoglobin and mitochondria. They have capillaries, which give them their red color. This type of muscle can contract for a long time without much effort.

Type I muscles can sustain aerobic activity using carbohydrates and fats as fuel. These muscles can contract rapidly and with a lot of force. The contraction is strong but short-lived. Compared with slow-twitch muscle, it is less dense in myoglobin and mitochondria.

Skeletal muscles are striated , which means that they consist of thousands of equally sized sarcomeres, or muscle units, which have transverse bands. A striated muscle appears striped under a microscope because of these bands. Different bands within each muscle interact, allowing the muscle to move powerfully and smoothly. It also depends on how you define a frown or a smile, he says. A deep frown will definitely take more muscles to pull off than a faint smile.

Taken another way, he says, elephants are thought to have the most individual muscles. Myoglobin is functionally similar to hemoglobin in blood; both contain iron and are responsible for carrying oxygen to the muscles myoglobin and throughout the bloodstream hemoglobin.

In fact, a high presence of myoglobin in the blood is a sign of extreme muscle injury, like rhabdomyolysis , which can be life-threatening. The high amount of myoglobin and subsequent oxygen in our muscle cells allows us to hold our breath for extended periods of time. Just like other animals, humans have both light and dark muscle. The color depends on the oxidation state of the iron atom bound to the muscle. When you lift weights, run, swim, or even walk briskly, this adds tension to your muscles, causing them to tear slightly.

Our bodies rebuild these tears by adding either sarcomeres, which are fibrous proteins inside muscle cells, or myofibrils—chains of rod-like units also in muscle cells that give them their striped appearance. More myofibrils will increase the mass of a muscle cell while more sarcomeres will increase the length. The more tension you place on your muscles, the more likely the muscle cells will tear, repair, and get stronger.

Just make sure you give yourself time to recover, or the healing process that leads to muscle growth will never actually occur. Nutrition is also key to building more muscle, and supplementing your daily diet with protein is a common way to facilitate muscle building with exercise, says Putrino.

But you also need plenty of calories , and carbs help support strength training and muscle growth, too. Clinicians call this phenomenon delayed onset muscle soreness , or DOMS. As Putrino explains, when you exercise your muscles, the subsequent contractions cause microtraumas to your muscle cells.

We build more muscle when those damaged cells repair themselves. One specific type of contraction, eccentric contraction—which happens when your muscles tense and lengthen at the same time—is the main cause of this cellular-level trauma. For example, when you do a typical squat, your quadriceps contract and lengthen as they lower. Importantly, resistance exercise also improves the connective tissue harness surrounding muscle, thus being most beneficial for injury prevention and in physical rehabilitation therapy.

Heredity differentiates the percentage and amount of the two markedly different fiber types. In humans the cardiovascular-type fibers have at different times been called red, tonic, Type I, slow-twitch ST , or slow-oxidative SO fibers. The proportions and types of muscle fibers vary greatly between adults. It is suggested that the new, popular periodization models of exercise training, which include light, moderate and high intensity training phases, satisfactorily overload the different muscle fiber types of the body while also providing sufficient rest for protein synthesis to occur.

Muscle Hypertrophy Summary Resistance training leads to trauma or injury of the cellular proteins in muscle. This prompts cell-signaling messages to activate satellite cells to begin a cascade of events leading to muscle repair and growth. Several growth factors are involved that regulate the mechanisms of change in protein number and size within the muscle.

The adaptation of muscle to the overload stress of resistance exercise begins immediately after each exercise bout, but often takes weeks or months for it to physically manifest itself. The most adaptable tissue in the human body is skeletal muscle, and it is remarkably remodeled after continuous, and carefully designed, resistance exercise training programs.

Additional References: Foss, M. Rasmussen, R. Exercise and Sport Science Reviews. He earned his master's degree in exercise physiology in and has research interests in the field of resistance training and clinical exercise physiology. Before coming to the U. Top of Page. Look for protein-rich foods that are also rich in the amino acid leucine.

You can find leucine in animal products like:. Learn more about high-protein foods ». How can you get started? The first step may be heading to your local gym and having a consultation with a personal trainer. Many gyms offer a free session as part of a membership promotion. A personal trainer can help you master the correct form with free weights, weight machines, and more.

Proper form is key for avoiding injury. Always remember to talk to your doctor before starting a new workout routine, especially if you have a health condition. They may have recommendations for exercise modifications that can help keep you safe. If you're looking to see gains in strength, you may wonder how to gain muscle without gaining fat. Here's a science-based breakdown of what works. Keeping your quads strong can improve the stability of your knees and reduce your risk of injuries.

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