The viscosity factor in muscle and muscle efficiency It is well at this time to point out that the initial heat represents partly that which is contemporaneous with the conversion of potential energy into mechanical work and partly with that which is employed in overcoming the internal friction and inertia within the muscle. The fluid parts of the muscle fibers are very viscous. This viscosity of the muscle fluids acting through the structural framework of the same muscle tends to retard the movement of structural framework of the same tends to retard the movement of contraction. of the potential energy developed within the muscle is required to overcome this internal resistance in the muscle machine. If a muscle contracts slowly less energy is required to perform a given amount of work than when it contracts rapidly. With the rapid responses the viscous muscle fluid must play through the structural framework with greater rapidity and thus increase greatly the friction and the proportion of the total energy developed which must be used for overcoming this increased internal resistance. Too rapid movements are, therefore, wasteful of potential energy and hence relatively inefficient. We may define the efficiency of muscle as in any mechanical device for performing work, as the relative part of the total potential energy expended which appears in the form of work. If muscular movements are carried out too quickly very little actual work is done by them and their efficiency is low; if, on the other hand, they be carried out very slowly a very large amount of work will be accomplished, but the amount of energy expended by the muscle in maintaining its contraction will be relatively too large and again the efficiency will be low. The maximal efficiency is attained at some intermediate point, that is, in order to obtain the greatest efficiency there is an optimal rate at which one can climb a flight of stairs, move a quantity of brick, make an excavation, or perform certain other tasks. It may be said that most of our implements with which we perform work have been adjusted so that they serve for the accomplishment of somewhere near the maximal amount of work. In activities such as running, the efficiency increases as speed diminishes. Although viscosity brings about an apparent wastage and diminishes muscle efficiency, it acts as a protection or "factor of safety" to the muscle machine. The viscosity of the muscles acts as a "brake" and prevents them from responding so fast as to tear themselves apart. Viscosity, therefore, tends to act as a governor of the speed at which mechanical work can be done and tends to hold it within the limits of safety.		Home Classes of levers Varieties of muscle Smooth muscle The blood supply to muscles The neurone Cardiac muscle On the nomenclature of skeletal muscles The nerve supply to muscles Structure of a skeletal muscle Central nervous system The reflex arc and reflex action Physiologic properties of muscle Mechanical Changes The effects of temperature on muscular contraction Muscle glycogen, its source and fate The reaction of muscles Oxygen consumption of muscle Determination of the oxygen consumption of muscle The viscosity factor in muscle and muscle efficiency Significance of the recovery heat Production of Electricity