Exercise in education and medicine / by R. Tait McKenzie.

  • R. Tait McKenzie
Date:
1909
Catalogue details

Licence: Public Domain Mark

Credit: Exercise in education and medicine / by R. Tait McKenzie. Source: Wellcome Collection.

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    mild, and there is less tendency to shortening and stiffening of the muscle so frequently found after extreme effort. Develop¬ ment is general rather than local, and Ions' distance runners are not noted for the thickness of their calves. General nutrition is best improved by the rhythmic self-massage of movement. “ Every muscle is a throbbing heart, squeezing its vessels empty while in motion and relaxing to allow them to fill up anew ” (Weir Mitchell). The element of skill does not play an important part in such habitual or automatic movements as walk¬ ing or running, so that their value in its promotion is compara¬ tively slight. Passive exercise improves the nourishment of the muscle-cell by forcing out the products of fatigue and keeping it bathed in a constantly renewed stream of arterial blood. This alone is suffi¬ cient to prevent wasting of substance in conditions where active movements are impossible, but it has little power to modify muscular strength or control. It can be demonstrated that the amount of blood in the muscle, as in the heart, varies with its contraction and relaxation. Mosso, of Turin, found that an arm inclosed in a water plethys- mograph (Fig. 9) diminished in volume on contracting the flexors and immediately increased above its original volume when they were relaxed. He also found an increase in the amplitude of the pulsations of the whole arm during and after the contraction of the flexors. These experiments have been confirmed by Sir Lauder Brunton and other observers, and it may be considered as conclusively proved that the blood-vessels are substantially enlarged in the active muscle after contraction, and during the contraction itself the interchange of products between blood and muscle is also accelerated. Not only is this true, but the actual nourishing power of the blood is augmented by this heightened activity. It has been proved by Hawk, in his interesting experiments on the blood-count of athletes in training1 at the University of Penn¬ sylvania, that various forms of active muscular exercise produce an average increase of 16.8 per cent, in the number of red corpus-