368 



THE HUMAN MOTOR 



Various oscillations occur in running. 



Suspension 

 Jfcjl* 



0*5 



1 second 



Fio. 264. 



Phases of running (Du Bois-Reymond). 



The head describes a 

 curve, of which the 

 lowest point syn- 

 chronises with the 

 moment when the 

 foot touches the 

 'ground. Chrono- 

 photographs prove 

 that the vertical os- 

 cillation in running 

 is less than in walk- 

 ing. The trunk oscil- 

 lates laterally, and is also subject to a slight torsion, which motions 

 are the more evident if the walker has a broad pelvis (as in the 

 case of the female figure) and short legs. As the rhythm and 

 speed increase these various oscillations become less. In effect, 

 the body remains in the " line of progression," which results in 

 economy of movement. Finally, for reasons already stated, the 

 arms oscillate in proportion to the speed. 



It will be appreciated, from the above remarks, that in running 

 the principal muscular work is effected by the flexions of the leg. 

 There is also contraction of the muscles of the hip and thigh at the 

 commencement of oscillation, and during the period of suspension. 

 The contraction of other muscles is also requisite to maintain the 

 equilibrium of the trunk. It is essential for quick running that 

 the thorax should be upright so that the runner can inhale deeply. 

 Experience also shows up that the best results are obtained in 

 running long distances by keeping the knees well bent, as there- 

 by the tiring oscillations of the body are reduced. 



Kgm 



120 



: 290 pas 



140 160 180 200 220 240 260 -.260 

 Fio. 265. 



Curves connecting expenditure of energy with number of 

 paces per min. (Marey). 



282. Muscular Work in Running. Attempts have been made, 

 by Marey and Demeny, to calculate the muscular work in relation 

 to the number of paces per minute. In fig. 265 are given curves 



