Would taking energy reserve before a cardio workout give you energy.

No.

Energy reserve is L-Carnatine, that's all. Lean Out has some L-C, but not nearly as much as ER. ER works best if used on a lower carbed diet and really is better when:

-Cycled, perhaps a 4 week on 2 week off.
-Closer to maintenance or below the maintenance level of calories.
-On contest diet, about 8 weeks out would be a good time to use it.
-Depending on Bev advisor and diet.

Frank