A System of Physical Education, Theoretical and Practical (extract)

I SECT. II.] EXERCISES OF PROGRESSION. 161 of the muscles shortly follows upon their contraction, fatigue will arise as readily and to as great an extent from want of this necessary interruption to contraction as from amount of effort. The answer to the opening question is thus virtually given in these remarks : when lying on the back the basis of support is equal to the entire body; it is, therefore, im- possible to disturb its equilibrium, not a single fibre of any muscle is called into action to preserve this position, it is one of perfect repose. ·when sitting, the basis of support is still large, being equal to the width of the hips. But as the trunk itself is held in an upright posi- tion by m1lscular effort, and as the head and neck can only be sustained in the line of the trunk by muscular effort, and as in this position there is little or no alternation of contraction and relaxation, a certain amount of fatigue is experienced in maintaining it; it is a position of semi- repose only. When standing, the basis of support is reduced to the space enclosed by the feet, while the line of the centre of gravity must pass through the elongated body, the heavie t portions being the farthest removed from the supporting La is; and thus the preservation of the equilibrium become a matter of muscular contraction; every finger lifted, every breath inspired and expired, chanO'e8 the centre of gravity and necessitates muscular contraction to re-aclju t aud re- establish it. From this erect position-in this erect position, more or less modified and varied by circumstance , all the modes of human locomotion are performed ,; and all the exercises in this section of the system are for the purpose of promoting the locomotive pow rs. These exercises arc walking, running, :M ! I l I .; ! l l ' : I I :..