58 MOTION AND LOCOMOTION 



the end of the step, the leg flexes at the knee and hip 

 and is carried forward in this bent and shortened form. 



Energy expended. In slow walking, the muscular 

 force required is but little in excess of that required to 

 support the body's weight. It is estimated to be one- 

 twentieth of the weight of the body multiplied by the 

 number of feet walked per hour. 1 In walking up or 

 down hill, the amount of power demanded is greatly 

 increased because of the fact that the body weight has 

 to be raised or lowered at every step. In bent-knee 

 walking, which has been experimented with for mili- 

 tary purposes, the body is allowed to fall forward, to be 

 caught by the swinging forward of the other leg. The 

 total effort required in rapid walking is thus some- 

 what reduced. In running, the body is tossed quickly 

 from one foot to the other, in addition to being thrust 



1 Thus a man weighing 150 pounds and walking at the rate of 4 



1 50 

 miles per hour, would exert K/rX 4 X 5280 ft. = 158,400 foot 



pounds per hour, or 2640 foot pounds per minute. A foot pound 

 equals the energy necessary to raise a weight of 1 pound to a 

 height of 1 foot. Corresponding to this are the units, foot ton, 

 which means the raising of 1 ton to a height of 1 foot; and the 

 1 rench unit, kilogrammeter, which means the raising of 1 kilogram 

 to a height of 1 meter. The energy required to raise 1 pound 10 

 feet is equivalent to that required to raise 10 pounds 1 foot, or 20 

 pounds 1/2 foot, and so on. 



a-- A t ? i Foot pounds Foot pounds 



per minute per day 



Bicycle riding, 10 seconds 19,000 



Bicycle riding, 60 seconds 8,750 



Soldier marching with load 5,000 3,000,000 



Climbing stairs for 8 hours 4,032 1,935.360 



Walking for 10 hours 3,987 2,394,000 



Using heavy hammer 5 hours 3,808 1,142,400 



Man pushing on lever in circular 



path 3,667 2,200,000 



Horse pulling on lever 17,166 8,500,000 



Working on treadmill 7 hours . . . 3,360 1,480,000 



Average work of man o . . 3,330 2,000.000 



