i beg do differ bro, studies show that at short periods of high intensity cardio are equal to longer less intense cardio sessions.....the reason the intense sessions are short is to prevent your body from tapping into protein within the muscle...jogging for 30+ min will cause a muscle burning effect, studies also conclude after 7-10 min jogging a persons body taps into the fat stores for energy, giving 10-13 minutes of rapid fat burning, you can do what you want to do, if you get bored easily jog for 20 min, if you love walking on a threadmill for an hour go for it...and no 20 minutes of jogging will not burn Muscle...
tbull