Yes, fatty acids are bound up in TriAcylGlycerol (TAG). Exercise triggers the breakdown of TAG in fat reserves, sending fatty acids into the blood. These fatty

Yes, fatty acids are bound up in TriAcylGlycerol (TAG). Exercise triggers the breakdown of TAG in fat reserves, sending fatty acids into the blood. These fatty acids go through a pretty complicated process to be delivered into a muscle cell, and then into the muscle cell mitochondria. This transport process cannot keep up with energy expenditure during intense exercise, thus the cutover to stored muscle glycogen (and at even higher peak loads under about 10 seconds, creatine phosphate). Sedentary people lose the ability to rapidly deliver fat into muscle cell mitochondria. This is a good summary of the current state of the research. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5766985/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5766985/