The authors propose that the enzyme hormone-sensitive lipase (HSL), which is the rate-limiting enzyme for hydrolysis of triacylglycerol in adipocytes, also regulates the intramyocellular triacylglycerol mobilization and is controlled by mechanisms similar to those regulating glycogen phosphorylase. From an exercise perspective, it is fascinating that the primary enzymatic setting allows simultaneous mobilization of all major extramuscular and intramuscular energy stores.