What happens to the gastrointestinal tract during exercise?
Exercise causes hypoxia, which increases the demand on the heart
to supply all the vital organs with oxygen. Therefore, being a
secondary property the GI Tract has blood flow reduced.
I don't know if that's what you're looking for, you might want
to search something more relevant to the whole body rather then a
system. For example "effects of exercise on the human body."
Exercise is sympathetic so decreases peristalsis and makes
vasoconstriction to blood vessel.