I was pondering Q&D with its mitochondrial benefits today, and in training fasted in particular. Pavel suggests it in the book, and adds that consuming an energy drink beforehand would negate the benefits. This makes sense if it’s an energy drink containing sugar but then I started thinking about sugar-free energy drinks - of which black coffee is one. When fasting (which is most days), I always have black coffee, so of course fasted training is still with a decent dose of caffeine in my system. Out of interest, I googled the effects of coffee on mitochondria and found this: Caffeine from four cups of coffee protects the heart with the help of mitochondria Based on that, it makes me think that coffee (or any sugar-free, caffeine-containing energy drink) is actually complementary to fasted Q&D training. Any further thoughts on this?