8 A BICYCLE ERGOMETER WITH AN ELECTRIC BRAKE 



as high as 100 to 120, or indeed, for short periods, to 135 or 140. To in- 

 crease the amount of work done it is necessary to alter not only the speed, 

 but more particularly the magnetic drag upon the disk. This is done 

 by increasing the current through the field. The lowest current that has 

 been used with the new instrument, either in actual riding or in the cali- 

 bration of the ergometer, has been 0.95 ampere, and the highest 1.5 am- 

 peres. With the earlier form of instrument, the current varied from 0.70 

 to 1.25 amperes. 



Certain fundamental criticisms can be made as to the propriety of 

 comparing the metabolism of a subject riding on a stationary bicycle 

 with that of a man riding a bicycle in the open air or on the track. Under 

 the latter condition there is a very rapid movement of air against the 

 body of the subject, with increased respiration, and hence a temperature 

 regulation due to the vaporization of water from the skin. There is also 

 a certain stimulus due to the presence of spectators. The psychical 

 conditions are unquestionably markedly different in ordinary bicycle 

 riding from those obtained when riding a stationary bicycle in the confines 

 of a laboratory, and especially in the confines of a respiration chamber. 

 That this psychical stimulation unquestionably plays an important role 

 in securing the greatest output of heat and mechanical work, particularly 

 in momentary special exertion incidental to a spurt, no one can deny. 

 On the other hand, experimental evidence thus far accumulated seems to 

 indicate that the relations between the total energy output of the body 

 and that actually transformed into heat by the ergometer remain for 

 the most part essentially unaltered; furthermore, it appears that although 

 under these conditions the psychical stimulation of actual riding may 

 possibly be conducive to greater muscular effort at the time, yet this 

 factor does not necessarily play any role with regard to the efficiency of the 

 body as a machine. The subject may have the personal impression that 

 the work done upon the bicycle ergometer in the confines of the laboratory 

 or inside a respiration chamber is a greater strain and requires more phys- 

 ical exertion than ordinary bicycle riding; on the other hand, we have 

 no evidence to indicate that experiments made upon this ergometer are 

 in any way physiologically abnormal. Indeed, the absence of the neces- 

 sity for balancing or steering the wheel might easily lead to a diminution 

 of the extraneous muscular effort incidental to outdoor bicycle riding, 

 and thus result in a larger proportional output of energy due to the leg 

 muscles. 



In using the bicycle ergometer the subject ordinarily rides for half 

 to three-quarters of an hour before the actual experiment begins. This 

 is more for the purpose of establishing a physiological equilibrium in the 

 body of the man than to adjust the apparatus to any particular condition; 

 during this period, also, there is a warming of the magnet coil to a con- 

 stant temperature and likewise a heating of the copper disk until it reaches 

 a point when the heat production is exactly equal to the heat lost through 



