This is an excellent question, and it all boils down to personal preference. Whether or not you react strongly to caffeine, stims, etc.
I think you should be all set, as I've found there to be NO CRASH with WF, and also for the energy to last me up to 4 hours after dosing.
My advice to you is try a dose before your cardio and see what happens. It should carry you through, no problem. If you have an off day where your tired to begin with, maybe you could carry an extra dose (pre-mixed in a bottle) in case you need to drink it following your cardio.
Let us know how it works for you!