How Muscles Work and How They Respond to Resistance Exercise

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Muscle contraction isn't just brawn. It isn't just mass that allows bodybuilders and powerlifters to perform Herculean lifts. Contraction of muscle, and strength in general, is much more than just size but also involves the muscle response to resistance exercise.

Anatomy and Physiology

There are three types of muscle in the body:

  • Skeletal (voluntary muscles that move the body, arms and legs)
  • Smooth (involuntary, found within the walls of internal organs, like stomach, intestine, bladder and blood vessels)
  • Cardiac (the muscle of the heart)

This article discusses skeletal muscle.

Skeletal muscle allows the body to move. The contractile tissue made up of thousands of parallel, cylindrical fibers that run the length of the muscle (you could have 100,000 fibers in your biceps alone!). The fibers are made up of smaller protein filaments called myofibrils that contain even smaller protein myofilaments called actin and myosin. The sliding filament theory of muscle contraction describes how actin and myosin slide over each other, causing the myofibrils to shorten, which in turn causes muscle fibers to contract.

Skeletal muscle allows the body to move. A muscle attaches on each side of a joint and when the muscle contracts or shortens, the joint moves. For example, the bicep muscle crosses the front part of the elbow. When you do a bicep curl, the muscle contracts, the elbow flexes and the weight is lifted.

Origins, Insertions, and Contraction Types