Muscle tissue represents the engine of our body

Through controlled contractions it makes us able to move our limbs and move in space. In addition it gives our body shape and esthetic structure

In our body there are more than 650 muscles, most of these appear in pairs located on opposite sides of the body. Muscles make out about 40% of our bodyweight

• Skeletal muscle or “voluntary muscle” that are anchored by tendons to bone and used to produce skeletal movement such as moving limbs,locomotion maintaining posture.

• Smooth muscle or “involuntary muscle” that is found within the walls of organs and structures such as the oesophagus, stomach, intestines, bronchi, uterus, urethra, bladder, and blood vessels. Unlike skeletal muscle, smooth muscle is not under conscious control.

• Cardiac muscle is also an “involuntary muscle” but is a specialized kind of muscle found only within the heart. Cardiac muscle is similar in structure to skeletal or striated muscle.

Skeletal muscle is further divided into several subtypes:

• Type I, slow oxidative, slow twitch, or “red” muscle is dense with capillaries and is rich in mitochondria and myoglobin, giving the muscle tissue its characteristic red color. It can carry more oxygen and sustain aerobic activity.

• Type II, fast twitch, muscle has three major kinds that are, in order of increasing contractile speed:

  • Type IIa, which, like slow muscle, is aerobic, rich in mitochondria and capillaries and appears red.

  • Type IIx (also known as type IId), which is less dense in mitochondria and myoglobin. This is the fastest muscle type in humans. It can contract more quickly and with a greater amount of force than oxidative muscle, but can sustain only short, anaerobic bursts of activity before muscle contraction becomes painful (often incorrectly attributed to a build-up of lactic acid). N.B. in some books and articles this type of muscle in humans was, confusingly, called type IIB

  • Type IIb, which is anaerobic, glycolytic, “white” muscle that is even less dense in mitochondria and myoglobin. In small animals like rodents this is the major fast muscle type, explaining the pale color of their flesh.

In general conversation though, one often refers only to slow or fast twitch fibers.

Cardiac and skeletal muscles are “striated”.They contain sarcomeres and are packed into highly-regular arrangements of bundles, smooth muscle has neither. While skeletal muscles are arranged in regular, parallel bundles, cardiac muscle connects at branching, irregular angles (called intercalated discs). Striated muscle contracts and relaxes in short, intense bursts, whereas smooth muscle on the other hand sustains longer or even near-permanent contractions.

The action a muscle generates is determined by the origin and insertion locations. The cross-sectional area of a muscle (rather than volume or length) determines the amount of force it can generate by defining the number of sarcomeres which can operate in parallel

In most muscles, all the fibers are oriented in the same direction, running in a line from the origin to the insertion. However, in pennate muscles, the individual fibers are oriented at an angle relative to the line of action, attaching to the origin and insertion tendons at each end. Because the contracting fibers are pulling at an angle to the overall action of the muscle, the change in length is smaller, but this same orientation allows for a larger amount of fibers contracting at the same time(thus more force) in a muscle of a given size.

If you’re serious about fitness and exercise it’s useful to learn a bit of anatomy and simple physiology. This makes the activity more enjoyable, as you know exactly what goes on in your body and why as you go along. This may also help spark your enthusiasm as there is always something new to learn.

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