Dear Welcome to HCM We understand your concerns I went through your details. Vyvanse is a central nervous system stumulant. It affects those brain parts which helps in hyperactivity and impulse control. You took it to have good performance in swimming. That is natural and many does it. Were you stressed and anxious prior to the swimming competition? That question eeds answer. Your answer is that answer. Don t worry. To be on a safer side, please consult a physician. If you still need my assistance in this regard, please use this link. http://goo.gl/aYW2pR. Please remember to describe the whole problem with full detail. Hope this answers your query. Available for further clarifications. Good luck.