@acid_fvs ok i’ll give u a overview of them, ok so there are 3 main energy systems used during exercise and they all work together. also the systems shift between one another based on what resources are available in the body. the first one is the phosphocreatine system also called ATP-PC, this is the fastest system for replenishing energy in the body, its also the fastest energy system to essentially run out of stamina, this is because the body’s stores of creatine are extremely limited, basically this system is typically the most active during short and high intensity movements, so like a 50 meter sprint. the second one is the lactate system also called anaerobic system, mainly uses carbohydrates, typically is most active during kinda short exercises like ones up to a minute, so like a 1000m race or like during points in tennis. and the last one is the aerobic system and it is the slowest and it’s mainly used during endurance stuff like a marathon. it’s the slowest cause it uses fats in the body to make energy which is usually a longer process, but the body has a ton of fat stores hence why it’s used for endurance