I've tried working out with weed in my system but for me it decreases muscle output and strength. It may have helped with cardio workouts though as when i used to run a few miles i noticed benfits from the bronchiodialation (spelling?) it seemed to have caused. Any drugs except testosterone boosters seemed to decrease strength but most increased cardio. May just be me, then again cannabis is said to signifigantly raise melatonin, the sleep tryptamine, which probably has to do with the lack of strength output. It also is said to block gaba to increase dopamine and everyone should know that gaba is a main component for building muscles. So all in all cardio yes, strength no, but that may be my personal chemistry, so to each their own :)