Why is it harder to work out on vyvanse (lisdexamfetamine)? i have to take bigger breathes and pain in stomach on the side sometimes-'runner side cramp'? thanks!

It may be causing an: Increase in your exercise hr. You might also be feeling some increased adrenalin, hence pushing harder. Consider using hr monitor for training & keep hr under 80% max. (or 'talk test' below) re abd pain-sounds like 'side stich' caused by diaphragmatic spasm. Watch your breathing, trying to breathe in thru nose & out thru mouth & only push hard enough to still talk in short sentences(talk test).