Your right a workout would work to shorten said effects due to its water soluble nature, meaning it would being released through sweat and urine (even more so since you'll hopefully hydrating during this workout). What your experiencing as 'prolonged' effects are the post workout natural increase in endorphins and other feelgood neurotransmitters (one of which would be dopamine, the same chemical Vyvanse casts its spell onto), which all work synergistically to produce a better feeling you. There isn't much you can do to extend the effects of Vyvanse since chemicals have a half-life or leave the body after a due to natural body function. There are many things that you can do to make the transition from high -> low smoother as well as getting the most out of your Vyvanse. Some of these are: STAYING HYDRATED, multivitamins (preferably with an extra Vitamin C supplement which is very important for neurotransmitter synthesis), l-tyrosine (precursor to dopamine, chemical Vyvanse uses up in brain, think about it as fuel for your brain :P), protein shakes (20g in morning and maybe one at lunch), eating healthy, working out, you know the drill. You should also take a look at supplements that can work to potentate and even work alongside the Vyvanse, I recommend this website. Chemicals like adrafinil, sulbutiamine, and racetams all have positive effects on how the brain operates and can work alongside Vyvanse. They aren't expensive either! But as always do your research before adding something to your body. All of these chemicals have an effect on many things whether they're positive or negative is subjective. Luckily many people have already done the experimenting and there is tons of information about these substance and there reactions with others. I hope this information goes to help you, have a great day/night!