Understanding the metabolic process — the means by which our bodies convert nutrients into energy — is a vital part of fine-tuning any workout regimen.
There are a few different ways to track the thermic effects of food intake, but all the energy we use to power our bodies comes from one of three metabolic energy systems: the anaerobic alactic (ATP-CP, or phosphagen system), the anaerobic lactic (or glycolytic system), or the aerobic.
By understanding how these energy systems operate, athletes can take advantage of the full array of benefits each provides, and fine-tune their workouts to the proper duration and intensity.
While most people talk about energy in broad strokes (they have it, they don’t have it), digging into the details of energetic processes helps athletes understand the dynamics of certain exercises, why some are harder to maintain than others, and what they can expect to experience during and after particular workouts.
What Is “Metabolism”?
Let’s start with the basics. At its core, “metabolism” is the chemical process that converts food into usable energy.
All energy is a result of converting high-energy phosphates (ATP) into lower-energy phosphates (ADP). This breakdown is called “hydrolysis”, and requires water, which is part of why proper hydration during workouts is so crucial!
However, since our muscles aren’t good at storing ATP, we have to resynthesize it. Hydrolysis and resynthesis become a circular process. ATP is hydrolyzed, resulting in ADP and a single proton. The ADP and proton combine and resynthesize ATP, and the cycle begins again.
Nevertheless, your own metabolic process may run slightly differently, depending on the immediate needs of your body and the type of physical stress it is under. These variations then result in the distinct energy systems discussed here.
For example: lifting weights requires an immediate and explosive kind of energy, while a jog through the neighborhood does not. That said, all three energy systems work in concert during any physical activity; while one may be predominant, all systems — phosphagen, glycolytic, and aerobic — contribute to varying degrees.
What Are The 3 Different Energy Systems?
The three energy systems each lend themselves to different types of exercise.
The anaerobic alactic (or phosphagen) energy system is best-suited for brief but intensive activities lasting ten seconds or less. In these situations, the body demands high amounts of ATP.
Creatine phosphate stored in muscles donates a phosphate to ADP to produce ATP. In this situation, no carbs or fats are used, and because oxygen isn’t necessary to this process, it is labeled “anaerobic”, meaning “without oxygen”. It is by far the fastest way to synthesize ATP, although due to the body’s limited stores of creatine phosphate, fatigue occurs very quickly.
Meanwhile, the anaerobic lactic (or glycolytic) energy system is harnessed during periods of intensive physical exercise that last from 30 seconds to two minutes.
Glycolytic energy systems involve carbohydrates — glucose or glycogen — that are broken down to form pyruvate. Every molecule of glucose yields two molecules of ATP, meaning energy compounds rapidly. When oxygen isn’t supplied rapidly enough to the muscles, hydrogen ions, stray protons, ADP, and potassium ions cumulatively known as metabolites build up inside the muscles, impeding muscle contraction abilities and decreasing muscle force production.
Last but certainly not least, the aerobic energy system is the most complex of all the energy systems. It is dependent on oxygen, and while it consistently supplies most of the body’s cellular energy, it is also the slowest of the three energy systems.
The aerobic system uses fat — the largest store of energy in the body — as well as glucose and glycogen to resynthesize ATP, ultimately yielding 18 times more ATP than anaerobic glycolysis.
How Do We Expend Energy?
There are a variety of factors that affect the amount of energy a person expends at any given moment. Age, gender, and physical fitness all affect how much energy is used at rest, during physical activities, or during essential bodily functions.
There are plenty of little, convenient ways to boost daily energy expenditure, such as choosing to walk short distances instead of taking public transportation or driving, swapping the elevator for the stairs, incorporating stretches and squats into your morning warm-up routine, or adding a step-count goal to your day or week.
How To Train Different Energy Systems
Because each energy system produces and maintains energy in vastly different ways, there are types of exercises that complement each one, allowing you to “train” each type of energy system optimally. As with all forms of exercise, proper training should be accompanied by periods of rest, and a steady intake of water and electrolytes.
The phosphagen system is best trained through brief sprints lasting no more than 20 seconds each. Then, with several minutes of rest between each set, you’ll be able to allow your body to replenish its stores of creatine phosphate.
The glycolytic system can be trained using intervals of up to two minutes, with a 1:2 ratio of exertion to rest. Try resistance training geared towards muscle building, or sprints of up to 400 meters.
The aerobic energy system lends itself to endurance activities and long-term but lighter exercises. Any time you exert yourself for longer than two minutes, you’ll need to add oxygen to the mix. The more efficiently your body is utilizing oxygen, the longer it can endure strenuous effort. The best way to train in this system is through a combination of continuous exercise and interval training. Begin with one hour of continuous exercise, then move into shorter, more strenuous tempo workouts.
The necessity of proper hydration can’t be understated; it’s crucial to restore fluids and electrolytes lost during physical exertion. Hydrating with conventional sports drinks isn’t always the best option, since many brands have an excessively high sugar content.
However, exogenous ketone drinks like Kenetik have zero added sugar, remain caffeine-free, and contain all the necessary electrolytes your body needs to keep you moving! Exogenous (i.e. externally sourced) ketones offer all the perks of endogenous (internally created) ketones and ketosis — a process in which your body produces energy by burning fat instead of carbs — without the hassle of keto dieting and intermittent fasting (although Kenetik is keto and fasting friendly!)
Ketones are an extremely efficient source of clean energy. With ketones in the mix, your heart and muscles can do up to 28% more work with the same amount of oxygen than they can with carbs alone.
Plus, ketones are known to lower oxidative stress and expedite muscle protein resynthesis. Drinking exogenous ketones induces the same metabolic shift as endogenous ketones, encouraging your body to burn ketones as fuel instead of your muscle’s glycogen. A bottle of Kenetik offers athletes a steady boost of clean-burning energy when they need it most. Power through with exogenous ketones, and elevate your exercise regimen with Kenetik. You’ll feel the difference.