54 EXERCISE. 



greatly tired, he has little appetite, sleeps badly, and next 

 morning still feels weary. His exercise, being more than 

 his body is suited to bear, has done him harm. Many 

 children (not to mention grown-up folks, who might be 

 supposed to know better) run about in the excitement 

 of some game, without realizing the fatigue, until after 

 they have greatly overworked and injured their muscles. 

 A walk of from six to seven miles daily is about the 

 proper amount of exercise for a grown person of ordi- 

 nary strength, whose business is such as to keep him 

 sitting most of the day and who is not able to take any 

 other outdoor exercise. Horseback-riding is better for 

 those who can afford it (p. 57). 



11. When to Exercise. Severe muscular work causes, 

 as we have learned, great muscular waste, and demands 

 an abundant supply of nourishment for the repair of the 

 muscles. For this reason, violent exercise should not be 

 taken after a long fast. Strong vigorous young people 

 may walk several miles before breakfast and not suffer in 

 consequence, but others had better wait until after eating, 

 before undertaking any great muscular exertion. Neither 

 should exercise be taken immediately after a meal. At 

 that time, a great deal of blood is needed in the stomach 

 and intestines to help in digesting the food (Chap. XI.); 

 and it cannot be drained off to supply the muscles as it is 

 during exercise, without risk of an attack of indigestion. 



12. Exercise should be Regular. When we work our 

 voluntary muscles, we give the heart and lungs more work 

 to do. The heart has to pump more blood to the muscles, 



11. Why is it not wise to undertake hard muscular work when fast- 

 ing? Just after eating ? 



12. How does muscular exercise affect the heart and lungs? What 



