THE GREAT BLUNDER: LOOKING IN THE WRONG PLACE
Medical science also focused on the biochemical nature of muscles. They found that myo-filaments, the smallest units of a muscle, consist of protein molecules (actin and myosin). These proteins in the presence of calcium go through a chemical reaction that make them slide past each other (like fingers of both hands sliding into each other's spaces to lock hands), shortening the length and thickening up to produce what we call 'contraction', or more accurately 'shrinkage'. Actually, neither those
proteins nor the muscle bulk contract in the true sense of the word. Muscles flex and extend, unlike solids which contract when cool and expand when heated. Muscle groups are classified as flexors when they move parts of the body together, and extensors when they move them apart. Thus the biceps of the arm is a flexor muscle because shortening it brings the hand closer to the shoulder and triceps is an extensor muscle as it does the opposite. Here flexion and extension are used to describe the movements. The two muscles (biceps and triceps), however, both 'contract' or shorten to be able to produce these movements. Thus 'contraction' is not the correct word to describe the genuine function of muscles and, as we will see later in the book, this word contradicts certain phenomena that take place in muscles. It is, however, only a technicality.
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Pain Relief-Muscle Relaxers