I say this is the wrong way to go about getting your body a workout. Like any muscle group, the group you work out for that day will become fatigued and tired when they are well and lacerated, or, when you've cut them enough inside the gym that they fill with blood and become worn. I could see a point in smoking weed before a workout (thereby opening blood vessels for better blood flow to your muscles and thus a slower onset of fatigue), but numbing your pain receptors so that your muscles can't cry save me until it is too late, in my opinion, is just plain silly.
Read some about body composition, and conditioning before you try and take shortcuts to the frame you want. I have more times than not been in the weight room and come close to injury simply from being too tired (or hungover, or high, or fatigued, etc, etc...) to lift my normal weight (or even 80% for that matter). Tread lightly, free weights are not to be coupled with shortcuts (steroids are a cowardly exception).
Safe travels.
;cancer