Human skeletal muscles.

Human muscles and their types

Each muscle of the human body is an organ that has its own origin, development, structure and location.
The muscles attached to the skeleton are called skeletal muscles.
They are made up of striated muscle tissue that contracts under the influence of nerve impulses.
Thus, the muscles provide the movement of the body in space, the maintenance of balance, respiratory movements, etc.
Muscles are the active part of the musculoskeletal system. Muscles are supplied with blood vessels and nerves. Striated muscle tissue, connected by loose connective tissue, forms bundles. The bundles of the first order are combined into bundles of the second order, the second – into bundles of the third order, etc. All bundles together form the muscular abdomen.

At the ends of the abdomen, layers of connective tissue form a tendon.
A tendon is a part of a muscle that attaches to a bone.
When contracting, the muscle abdomen shortens, and the tendon pulls the bone behind it, which plays the role of a lever when making movements.

Muscles are distinguished according to the movements performed:

• flexors (flexion of the limb);
• extensors (limb extension);
• adductor joint (adduction);
• abductor joint (abduction);
• rotators of the joint (rotating movements), etc.

As a rule, several muscle groups are involved in the movement of a joint.
Synergists are muscles that are jointly involved in the movement of a joint in the same direction.
Antagonists are muscles that are jointly involved in the movement of the joint in the opposite direction.
The involvement of different muscle groups makes the movements precise and smooth.

Example:
the antagonists in the elbow joint are the biceps muscle, which provides flexion, and the triceps muscle, which provides extension.

Muscle performance

When the limb moves with the contraction of the flexor muscles, the extensor muscles relax, and vice versa.
But with a constant load (holding the kettlebell on an outstretched arm), the extensors and flexors will be synergistic, since their action will be directed in one direction.

Muscle performance depends on the magnitude of the load and the rhythm of work. It can be increased with training.
A systematic dosage load increases the blood supply to the muscles and the bones attached to them, which leads to the strengthening of the body’s musculoskeletal system.
Prolonged muscle inactivity can lead to muscle atrophy – destruction of muscle fibers and loss of performance.