Carbon dioxide is produced as a metabolic waste product from exercise. Any sort of fat-burning you want to do is limited by the rate at which you can exhale CO2. This is why vigorous exercise is accompanied by heavy breathing. This includes not only cardiovascular training but also weight training. Lifting heavy weights will have you breathing very hard!
Unfortunately, if you don’t lift heavy (or if you use electrical stimulation that’s mild enough to sleep) then you’re not going to put your muscles into hypertrophy, so you won’t gain muscle mass either.
Unfortunately, if you don’t lift heavy (or if you use electrical stimulation that’s mild enough to sleep) then you’re not going to put your muscles into hypertrophy, so you won’t gain muscle mass either.