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Using one of the thigh muscles of the human as a good example of a powerful muscle, we can make some basic comparisons with the great breast muscles, known as the major pectoral muscles of the racing pigeon. Recall that the major pectorals are the largest muscles in the body of the pigeon and make up 20% to over 30% of the total weight of the bird. They are the large muscles that we feel with our fingertips as we handle a bird. At the microscopic level, we can see that the large breast muscles are made up of elongated, cigar-shaped cells that, by convention, have been called fibres whose tapered ends attach to one another to make up the entire muscle. These cells are called fibres because when delicate micro-techniques are used to tease them out, they resemble fine threads or fibres.

In the breast muscle of the pigeon, there are only two types of muscle fibres, one a narrow diameter fibre, and the other, a broad-diameter fibre. In cross section, these fibres are round or oval. They are arranged in bundles, with the broad-diameter fibres on the edge of each bundle for the most part, and the narrow-diameter fibres located more deeply within each bundle. (A very rough, comparable example would be a number of thick and thin cigars tied together by a rubber band. For the most part, the thick cigars would touch the rubber band, whereas the thin cigars would be located more deeply within the whole bundle of cigars.) Many thousands of bundles of fibres, arranged end to end and beside one another, make up the entire muscle we feel with our fingers.

The broad-diameter fibres are known as white fibres, whereas the narrow- diameter fibres are known as red fibres. Red fibres far outnumber white fibres. For every white fibre, on average, there are approximately 14 red fibres. In actual repeated counts of 100 fibres at a time, Dr John George, the dean of muscle research in pigeons at the University of Guelph in Ontario, Canada, determined that between five to 14 were white fibres, and 86 to 95 were red fibres.

Why are these facts of value to us as racing pigeon fanciers? Well, the white fibres in the major breast muscles have very fast contraction velocities (that is, the speed at which they operate or twitch), ranging from 31-37 milliseconds. A millisecond is 1/1000 of a second, which means that one complete contraction or twitch of these white fibres takes a mere 31/1000 to 37/1000 of a second! At such rapid velocities, the white fibres are utilised for extremely swift, even explosive actions, such as launching from the transport truck, sudden dodging bursts of speed during flight, and braking to land, etc. - in fact, any action that causes the wings to beat faster. As well, one can obtain a further practical appreciation of the speed of these fibres by noting the rapidly trembling wing tips of a bird in top form, or one shivering on a cold day.

Now, because they twitch so quickly, white fibres also become exhausted very rapidly, and for this reason, could not be expected to handle sustained flight, but instead, they deal with sudden, even explosive emergency flight.

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