MUSCLE 287 



a nerve-muscle preparation as a slightly heavier one. No satis- 

 factory theory of this reaction to load has yet been formulated. 

 Explanations have been put forward, but they merely substi- 

 tute one unknown for another, a not uncommon drawback to 

 explanations. 



Muscles are strongest when at their full physiological length. 

 As he dips an oar into the water a man exerts the greatest force 

 of which he is capable, provided that he is not guilty of 

 " missing the beginning." Hands over the stretcher, body 

 between the knees, ankle, knee, hip, fully flexed, arms straight 

 all his strongest muscles are at their greatest physiological 

 length. Rowing is an exercise which has no rival. Every 

 muscle in the body, from little toe to little finger, comes into 

 play under the conditions which suit it best. And not less 

 admirable is the effect upon the abdominal muscles during 

 recovery at the end of the stroke ; and the rhythmic movement 

 which encourages deep and measured respiration. 



The greatest output of work is obtained when muscles con- 

 tract against a progressively diminishing load. Towards the 

 end of the lift the load must be small, if contraction is to be 

 carried to its extreme limit. The provision for this is well seen 

 in the case of the muscles of the arm when lifting a weight up 

 to a position above the head. A portmanteau is held in the 

 hand. Its handle is gripped by flexing the fingers. And here 

 it may be noted that, since the range of movement of a muscle 

 varies as its length, the thumb and fingers are not worked only 

 by muscles contained in the palm of the hand. Fingers are 

 bent and wrist flexed by muscles of which the origin is carried 

 up even to the lower end of the humerus. As the portmanteau 

 hangs by the side, biceps and brachialis are at their fullest 

 length. Suppose it to be necessary to place it on a cab. These 

 muscles begin the work under the best conditions. They could 

 not, however, lift the portmanteau far did not the muscles of 

 the shoulder displace the elbow from the side, so that at the end 

 of their pull, the forearm being almost vertical, the muscles of 

 the arm have little more to do than to move the hand inwards 

 towards the head, in preparation for the extensor thrust. 

 The secret of getting the greatest amount of work out of any 

 particular muscle lies in securing for it the due co-operation of 

 other muscles. 



