Efficiency of Grade Climbing In walking or running up a slight grade most of the energy expended is used in movements of the arms and legs and is dissipated as heat; very little is used in actually raising the body. As the grade becomes steeper, more of the total energy expenditure is applied to raising the body and the work efficiency is accordingly increased. Estimates of the work efficiency of movement up a slight grade are practically useless for assessing the mechanical efficiency of the entire body. They are of some value when the efficiencies of two or more individuals are to be compared. For this purpose, the energy expenditure of each subject performing the same run is measured; the lower the energy expenditure the higher is the efficiency. Steeper grades or higher rates of climbing differentiate more clearly among individuals because of the greater stresses involved. Energy Cost of Progression The comparative efficiencies of walking, running, climbing and performing other forms of progression at various speeds along the horizontal or up varying grades may be evaluated by comparing the energy expended in traveling a fixed distance, such as a mile. Very slow rates of progression which are performed with low expenditures of energy are not efficient. Moving slowly to "save energy" is false economy when a certain distance has to be traversed. Table VII shows the energy expenditure at various speeds and grades of different types of progression. Here is demonstrated the principle that the most efficient speed for a certain form of progression is not proportional to the rate of energy expenditure (Cals./hr.), but rather to the quantity of energy used during each unit of distance (Cals./mile). Fewer Calories are used in walking a mile at 3.5 m.p.h. than when the speed is slowed to 2.3 m.p.h. or increased to 4.6 m.p.h. Speeds of grade climbing below 2.5 m.p.h. require the expenditure of more Calories each mile than do speeds of 2.5 to 3.5 m.p.h. Less energy is expended when a 43 pound load is carried at 3 m.p.h. than at either slower or faster speeds. In carrying the load up a steep grade, the faster speed is more economical, but at the greater speed the rate of energy expenditure becomes so high that a steady state of physiological activity cannot be established and exhaustion occurs within a short distance. In the case of grade walking carrying a 43 pound load, it would appear that 1 m.p.h. is the optimal speed if the load is to be carried more than a mile, but 1.5 m.p.h. is optimal if the load is to be carried less than a mile. The same principles apply to skiing along the level. The faster speed is more economical but the high energy requirement at speeds above 5 m.p.h. prevent these rates from being continued for more than one hour. The rapidly increasing energy requirement as swimming speed is increased necessitates a moderately slow rate of swimming if the distance to be covered requires more than one hour. Extremely slow rates of swimming are uneconomical.		Home Pace Motivation Measures of Endurance Computation of Dietary Requirement Work Efficiency Maximum Steady State Work Inefficiency of Anaerobic Work Estimation of Work Efficiency Efficiency of Grade Climbing Low Economy of Slow Work Maximum Rate of Work Levers of the Body Fatigue and Recovery General Fatigue Symptoms Anxiety State Organic Fatigue Cortical Motor and Sensory Centers Effect of Exercise on Mental Work Visual Fatigue Muscular Fatigue Fatigue Prevention and Recuperation