166 THE HUMAN MOTOR 



1. Proportional to the weight lifted P ; 



2. ,, to the degree of contraction r. 



In the absence of mechanical work all the energy expended is 

 dissipated into heat. Therefore, the only result of a static effort 

 is the production of heat, which raises the temperature of the 

 contracted muscles. Examples ( l ) : 



(a) A variable weight was lifted by contracting the biceps 

 muscles uniformly. The temperature rise was as follows : 



Weight lifted 1 kg. 2 kg. 5 kg. 



Temperature nn 2' 0-17C 0-32C 0-98C 



rise Jin 4' 0-25C 0-58C M5C 



The relation of the temperature rise to weight and time is not 

 doubtful, in spite of the difficulty of taking the measurements 

 (a thermometer, capable of indicating to T J n of a degree, was 

 applied to the muscles). 



(b) When a constant weight of 2 kilogrammes (P, fig. 134) was 

 held with the forearm having angles of flexion varying from 40 

 to + 40, for periods of two minutes, the following results were 

 obtained : 



Angle 40 20 +20 +40 



0-28 0-50 0-67 0-78 0-88 



We may also consider the effect of load and muscular contrac- 

 tion on the consumption of oxygen. ( 2 ) 



(a) When sustaining a variable load by a constant muscular 

 contraction the following lesults were obtained : 



Weight If kg. 3ikg. 5kg. 



Additional consumption of oxygen ... 119 cc. 204 cc. 319 cc. 



These are fairly exact proportions, 

 the oxygen representing here the 

 difference between the consumption 

 during the static effort and the con- 

 sumption before the experiment (in 

 repose). The Calories may be esti- 

 mated at 4-60 per litre, the subject 

 having fasted. Then from the above 

 table the expenditure may be cal- 

 culated to be 0-547, 0-938 and 1467 

 Calories respectively. 



(b) For an effort of 5 kilogrammes 

 FI. lav. an( i variable angles of^flexion. 



(*) A. Chauveau (Journal de PhysioL, 1899, p. 157 ; 1900, (313). 

 ( 2 ) A. Chauveau and Tissot (Comptes Rendus Sciences, vol. Ixxiii., p. 1236 ; 

 1896, and Arch, de PhysioL, 1897, p. 78). 



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