This is due to the fact HIIT can handiest use glucose as electricity. When your body reaches - of its maximal depth, the anaerobic threshold kicks in and the body has to apply glucose handiest. Glucose is sincerely referred to as blood sugar, or "carbohydrates" after they input the body. When a deficit of carbohydrates are gift, then the frame turns to the amino acids or phosphate creatine to make ATP strength. On the other hand, HIIT lasts nowhere near as long as LISS, so that you may want to argue that HIIT truely burns an insignificant amount of muscle in the contrast.