AJP - Regulatory, Integrative and Comparative Physiology, Vol 246, Issue 4 495-R501, Copyright © 1984 by American Physiological Society
Body composition in the rat: interactions of exercise, age, sex, and diet
G. C. Pitts
Changes in rat body composition (15 components) associated with changes in
level of physical activity (cage restraint, ad libitum activity in living
cages, and ad libitum wheel running), age at initiation of regimen (22
days-16 wk), sex, and diet (chow and 60% fat) are evaluated. Running
regimen initiation at 7 wk of age or younger is associated with a decrease
in the fat-free body mass (FFBM) in males and an increase in females.
Initiation at 11 wk or older does not change FFBM. Both reduce body fatness
in either sex. Age altered the mass of 11 components, diet altered the mass
of 10 components, and activity altered the mass of 8 components, and there
were 6 interactions between the experimental variables. The significance of
interactions in general is discussed. Our data together with those of other
investigators indicate that the responses to volitional wheel running and
forced treadmill running are similar, but data from swimming rats may not
be comparable in some cases.
