Validity of Ergo graph as Measurer -o/ Work Capacity 7 



So much for the positive phases of practice effect. Of the 

 negative effects we may mention, first, — that acts which have 

 become habitual require less voluntary effort for their perform- 

 ance than unfamiliar movements. When an unskilled bicycle 

 rider tries to ride up hill he must have his attention upon the 

 task constantly, and the mental strain is very noticeable. After 

 practice the task is accomplished better without conscious direc- 

 tion. Secondly, distractions are less likely to draw one away 

 from work in which one is well practiced. Telegraph operators 

 who are new at the business are bothered very greatly by the 

 otber sounders when they are obliged to work in a room with 

 many operators. But with practice they can listen to the click 

 of their own sounder and are not disturbed by the confusion 

 about them. Thirdly, voluntary effort usually becomes less irk- 

 some with practice. The feelings of weariness and tiredness 

 intrude themselves less and less, and in case the routine does 

 not become monotonous, we come to enjoy the task which we 

 dreaded at first on account of the disagreeable results attendant 

 upon the performance. After one is inured to the work and is 

 accustomed to the machine, as in the experiment with the ergo- 

 graph, there is enough novelty about the investigation of new 

 problems to make the task enjoyable although the same old move- 

 ment is performed day after day for weeks together. All the 

 foregoing statements are based upon ordinary empirical obser- 

 vation ; but before they can be considered as scientifically estab- 

 lished it is necessary to study these phenomena under uniform 

 conditions and circumstances which can to a great extent be 

 controlled. 



Physiological Considerations. — On the side of the organism, 

 changes resulting from exercise can take three possible direc- 

 tions : 1, Changes in the muscles themselves which are exercised; 

 2, changes in the nervous control of these muscles ; and, 3, 

 changes in the blood supply for both muscles and nerve centers. 



The changes in the character of the muscles will, as we have 

 described, be a hardening and toughening of the muscle sheaths, 

 rendering them less likely to become inflamed through the rub- 

 bing and twisting which they undergo during contraction. The 



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