ABSTRACT
Physical activity also seems to be stimulated by sym-
pathetic activity. The positive relationship between spon-
taneous physical activity and norepinephrine appearance
rate is consistent with the idea that SNS activity is a
determinant of individual differences in the level of spon-
taneous physical activity, i.e., how much people move
around, change position, and fidget, all of which contrib-
ute to total energy expenditure. So “fidgeters” seem either
to have a constitutionally higher SNS activity (5) or to
possess certain functional polymorphisms in genes con-
trolling the activity of b-adrenoceptors and uncoupling proteins (7,8).
