PHYSICAL ACTIVITY AND ENDURANCE. 641 



sex is closely associated with metabolism and is probably more or less 

 dependent on the metabolic level. These investigators have shown 

 that by modifying one they may modify the other. It is commonly 

 beUeved that the sex instinct is stronger in men than it is in women. 

 The large amount of metabolism data from this laboratory and other 

 institutions has proved that the metabolism of men is higher than that 

 of women. It is not, therefore, illogical to believe that a lowered meta- 

 bolism in men may reduce or even obliterate sex interest. 



PHYSICAL ACTIVITY AND ENDURANCE. 



The important relationship between muscular work and total meta- 

 bolism made it incumbent upon us to obtain all possible information 

 with regard to the relative physical activities of these groups of men 

 and their college mates. The diet was to be reduced by design. If the 

 physical activity were likewise considerably reduced, it is obvious that 

 the diet might still be a maintenance diet without a material alteration 

 in the general condition of the body. While the main criterion was to 

 be a reduction in weight of 10 per cent, which would inevitably take 

 place if the supply were materially less than the demand, it still would 

 definitely disturb the relations of the experiment if the subjects reduced 

 the physical activity appreciably. The men were repeatedly instructed 

 and, indeed, urged to keep their bodily activities as nearly normal as 

 possible. It was impressed upon them that the aim of the experiment 

 was to study the effect of a reduced diet upon the efficiency of a group 

 of men in carrying out the ordinary activities of the collegiate life. 

 If they voluntarily and deliberately reduced these activities at the 

 beginning they would not be fulfilling the prime condition of the experi- 

 ment and would seriously vitiate the results. 



These men were all college students and had the regular college 

 program to carry out. This involved a certain amount of walking to 

 and from classes in the different buildings and to the main dining-hall 

 for the several meals, also the gymnasium work prescribed in certain 

 college courses. Furthermore, as with most college students, walking 

 was a regular form of exercise and recreation outside of the prescribed 

 college work. 



One development we did not anticipate was the fact that in many 

 instances the men made special efforts to reduce the weight at the 

 beginning of the experiment. To hasten the loss of fat and thus reach 

 the 10 per cent level quickly, they indulged in unusually strenuous and 

 prolonged exercise. The subjects reasoned that the sooner the desired 

 weight reduction was attained, the sooner they would receive larger 

 amounts of food to hold them at this level. This same increase in 

 physical activity appeared several times throughout the course of the 

 experiment, particularly after the uncontrolled Sundays, the short 

 Thanksgiving recess, and the Christmas vacation. 



