Part 1: Science of Energy System Development.
Hello, Fortified Body Gym family and fitness friends! Today, we are about to turbocharge our way into the powerful, occasionally uncomfortable and always sweaty world of energy system development. We’ve all experienced it, that moment when you have jumped into a workout with your engines raring to go, you accelerate into the session, feeling like nothing can stop you, when all of a sudden your fuel gauge just hits empty and you come to a spluttering stop or at best sad slow jog, as you hold on for dear life to make it to the end of the workout . That dip in energy isn't just mental, there’s some fascinating science behind it. In this first of our three-part energy systems crash course, we’re here to break down how your body uses fuels and how you can train smarter to last longer, get fitter and healthier, to help you fortify your body from the inside out.
What Exactly Are Energy Systems?
Think of your body as a high-performance hybrid vehicle with multiple fuel modes. Just as this type of car switches between engine systems for different driving styles, your body utilises different fuel systems depending on whether you're revving up for a sprint, hauling a heavy campervan or just cruising along at a steady pace trying to dodge kangaroos. Here are the three main energy systems powering your body through workouts:
1. ATP-PC System (The Nitrous Boost)
This is your body’s quick-response, instant-energy system—think of it as your nitrous boost. It taps into stored ATP (adenosine triphosphate) and PC (phosphocreatine) to give you an instant, explosive burst of energy, but only for a short distance. Imagine a drag racer: you hit the accelerator pedal and then press that nitrous boost button and boom!! in the next 10–15 seconds, you hit top speed. After those few seconds, though, the nitrous (stored ATP & PC) is depleted, you have to switch to the next system, and you start to slow down. The ATP-PC system is fast and furious, and over before you know it. This is perfect for those “wham, bam, thank you, ma'am” moments in fitness. 😉
2. Glycolytic System (Your Turbocharged Engine)
When the ATP-PC system is tapped out, the glycolytic system steps in. This is primarily an oxygen free process known as anaerobic glycolysis. Think of it as your car’s turbocharger, ready to step in and keep you racing for activities lasting between 15 seconds and 2 minutes. This system quickly converts glucose into ATP, our bodies A-grade fuel, without the need for oxygen, giving you energy fast. However, as with most good things in life, this doesn’t come free, there’s a trade-off. This produces a few “negative” by-products, including lactate, hydrogen ions, and inorganic phosphate. Just as a turbo engine can overheat, these by-products accumulate and can start to make your muscles feel overheated and overworked, creating that familiar burning sensation that forces you to ease off the throttle and ultimately will begin to slow you down. The glycolytic system’s rapid energy production makes it ideal for short, intense bursts of activity but limits endurance by causing fatigue over time. “I feel the need, the need for speed!”
3. Aerobic System (Your Hybrid Engine)
Finally, we have the aerobic system—the body’s hybrid engine, built for endurance. Just like a fuel-efficient car that switches to electric when minimal power output is required, this system is in used at rest and during low- to moderate intensity activities. The aerobic system uses oxygen to steadily convert carbohydrates (through aerobic glycolysis) and fats (though beta oxidation) into ATP. This all occurs at a cellular level in your mitochondria (the body’s micro powerplants). While the aerobic system doesn’t produce nearly as much power as the other two systems, nor is it as quick as the first two systems, it is highly efficient and produce almost an unlimited supply of ATP which can keep you going for hours of moderate effort, depending on your fitness level of course.
Whether you’re drag racing it or pacing yourself for the long haul by understanding these systems, you’ll be able to train smarter and unlock different “fuel modes” for greater performance and health. Stay tuned for Part 2 as we explore how to fine-tune your energy systems and get the most performance and mileage out of your workouts.
