32 J'lxlier — Tlie Effect of Diet on Endurance. 



fore j)t'ifectly uniform for all the men ; it showed how many con- 

 tractions were necessary in each case to bring down the strength of 

 the biceps from 50 to 25 ; it showed how much the muscle could 

 endure before being robbed, by fatigue, of half its strength. Thus at 

 the beginning the strength is 50 lbs.; after the first contraction it is, 

 say, 49 ; after the second, 48, etc. But the contractions continue until 

 the strength sinks below 25 lbs. The loss of strength may be said to 

 measure fatigue. The sloioness of this loss may be said to measure 

 endurance and is well indicated by the number of contractions 

 necessary to tire a muscle from a strength of 50 lbs. to a strength of 

 25 lbs. 



Four exceptions, however, need to be noted. Three men, B., Lw. 

 And P., wei'e unable in January to raise the 50-lb. dumb-bell at all 

 (see Table XII). Consequently their January test with the 25-lb, 

 dumb-bell did not begin at 50^ of the strength, but at a higher frac- 

 tion. This explains their high apparent improvement. Thus, Lw. is 

 credited Avith an im])rovement of 450fc, because in January he could 

 raise the 25-lb. dumb-bell only 6 times, and in June, 33 times. 

 But the 33 contractions in June began at just 50^^^ of the strength of 

 the muscle, owing to its pi"evious exhaustion to the 50-lb. level by 

 the 50-lb. dumb-bell, whereas the six contractions in January besfan 

 at a higher level; for at that time the biceps could not raise the 

 50-lb. dumb-bell at all. Its strength was at that time less than 50 

 lbs., say 40 lbs., in which case the lifting of the 25-lb. dumb-bell 

 required not 50^^^ but Q2^'fc of its strength. To compare a 50^ test of 

 June with a 62^^ test in January gives a record of improvement 

 which is not one of pure endurance, but which includes the element 

 of increased strength. This is " endurance " in the crude sense in 

 which we may say a man has more endurance for carrying trunks 

 than a boy ; but for a comparison of pure endurance, the boy should 

 be given smaller trunks to handle than the man. 



The fourth case is E., to whom the reverse reasoning applies. In 

 June when he reached test 6, he was unable to raise the 50-lb. dumb- 

 bell at all, though in January he had raised it once. Hence, while 

 the 25-lb. dumb-bell was a 50^ test in January, it was a more 

 severe one in June, and the -44,^^ which records his falling off does 

 not represent a pure loss in endurance, but partly also a loss of 

 strength. To reckon /?w/-e endurance we need to bring -44 up toward 

 zero. 



Making the four omissions just mentioned, we may use the remain- 

 ing records from the last line of Table XIII, as a barometer of 2>ure 

 endurance. 



