Andrew Huberman· PhD
Our muscles and our neurons use different fuel sources to generate ATP. The ones that are used first for short bouts of intense activity are things like phosphocreatine. If you've only heard about creatine as a supplement, well, phosphocreatine actually exists on our muscles. That's why people take creatine, you can load your muscles with more creatine. Phosphocreatine is great for short, intense bouts of effort. Then you start to tap into things like glucose, which is literally just carbohydrates as just sugar that's in your blood. Then if you keep pushing, you start to tap into other fuel sources like glycogen, and you have fats stored in adipose tissue. Even if you have very, very low body fat percentage, you can extract lipids, fatty acids from that body fat. It's like a storage pack, it is a storage pack for energy that can be converted to ATP.