4 A BICYCLE ERGOMETER WITH AN ELECTRIC BRAKE 



Recently a brake ergometer employing bicycle pedals has been used 

 with considerable success by Amar, 1 while in a private communication 

 Dr. Krogh writes of a bicycle ergometer which he is using in collaboration 

 with Dr. Lindhard, in which the principle of the electric brake plays an 

 important role. 



Numerous tests have also been made to compute the energy trans- 

 formations of a bicyclist while traveling on the track against the resistance 

 of air, wheels, tires, and chain. This was considered by Prof. R. C. Car- 

 penter 2 in connection with the amount of energy consumed in a bicycle 

 race, but was much more satisfactorily determined by Berg, duBois 

 Reymond, and Zuntz 3 by means of a bicycle towed around the track by 

 a motor cycle. In every instance thus far cited, it was necessary to con- 

 vert the foot-pounds or kilogrammeters into calories, the accuracy in the 

 measurement of foot-pounds or kilogrammeters being the criterion of the 

 apparatus. In practically all instances, owing to the difficulty of determ- 

 ining these mechanical quantities exactly, the apparatus was by no means 

 so accurate as the best physiological experimenting can to-day demand. 



Certain muscular exercises, such as swimming or rowing with sliding 

 seats, unquestionably bring into play more muscles than does the exercise 

 of bicycle riding; on the other hand, the stationary position of the body, 

 particularly of the head, makes the exercise of riding on a stationary bi- 

 cycle distinctly advantageous for a study of the respiratory exchange, 

 especially when the subject has to breathe through a mouthpiece or nose- 

 piece, or through some other form of breathing appliance. Furthermore, 

 as has been frequently demonstrated, most intense muscular exercise can 

 be produced by means of the powerful leg muscles; hence, in any study of 

 metabolism during muscular work, all of these advantages seem to point 

 toward the desirability of utilizing some form of bicycle motion for the 

 muscular work. 



The great difficulty with the earlier types of bicycle ergometers, how- 

 ever, has been the uncertainty of the amount of work performed, for even 

 with the apparatus of Atwater and Benedict there was considerable slip 

 of the contact, and the determination of the work done was by no means 

 satisfactory. With other forms of ergometers, in which there is the fric- 

 tion of a band, or belt, or weight, the uncertainty and variations in the 

 resistance must always be reckoned with. 



Mr. 0. S. Blakeslee, formerly mechanician of Wesleyan University, 

 made the ingenious suggestion that an electric brake be used for applying 

 a constant source of resistance in a bicycle ergometer. This later form 

 of apparatus consisted essentially of a bicycle, the rear wheel of which was 

 replaced by a copper disk which rotated between the pole-faces of an 

 electro-magnet. The usual form of pedal, sprocket-wheel, and sprocket- 



1 Amar, La Rendement de la Machine humaine, Paris, 1910. 



2 Atwater, Sherman, and Carpenter,U.S.Dept.Agr., Office Exp.Stas.Bul.98, 1901, p. 57. 

 2 Berg, duBois Reymond and Zuntz, Arch. f. Anat. u. Physiol., Physiol. Abt. 1904, p. 20. 



