Written by Garett Reid | NSCA, CSCS, CISSN, M.S.E.S.S
Fact checked by Kiel DiGiovanni, Co-founder
FACT CHECKED
Have you heard of ATP? You probably have, but have you wondered why it's called ATP? Well, because of its full name, adenosine triphosphate, it takes too long to say. Putting the name aside, ATP is spoken about a lot in the fitness world, but people rarely go into detail about what it is. This article will explain what ATP is and why it might be the most essential compound in fitness.
What Is ATP?
ATP is short for adenosine triphosphate. That may not mean much to you, but its importance is seen in its name, specifically "tri-phosphate." Let us explain.
A single molecule of ATP consists of adenine (a nitrogen base) and a molecule of ribose (a sugar molecule), forming adenosine. In addition, three phosphate groups are attached.
When adenosine has just one phosphate, it is known as adenosine monophosphate (AMP). If it has two phosphates, it is referred to as adenosine diphosphate (ADP), which will be important later as we discuss its function.
As a whole, ATP is a high-energy compound that plays numerous roles within the human body. However, its primary purpose is acting as the body's "energy currency." That is, ATP provides the energy required to power an array of various cellular reactions and processes.
How Does ATP Store Energy?
The phosphate chain within ATP is the energy-carrying part of the molecule. This is where the magic occurs, giving it its power.
Remembering a few basic chemistry principles to grasp what's happening is helpful. When bonds form between atoms and molecules, they store energy. This energy remains in the chemical bonds until they break.
When these bonds break, energy is released in an exothermic reaction. This is particularly important in the case of ATP, as the bonds are particularly strong because the atoms in the phosphate chain carry a high negative charge.
This negative charge drives them to seek out positively charged molecules to stabilize their charge. When these negatively charged phosphate groups are released, they achieve a more balanced state.
Regardless, when a phosphate of ATP breaks off, this energy is released and enables the cell to perform various functions. Further below we'll go through some of the major functions powered by ATP.
How Much ATP Does Your Body Have?
The amount of ATP a body has largely depended on the person's weight, but we'll put it like this.
- Your body has around 37 trillion cells
- At any given point, a single cell holds about 1 billion molecules of ATP
- On average, a single cell in the human body utilizes around 10 million ATP molecules every second.
- A cell can recycle all its ATP in around 20-30s
- In 24 hours, the human body replaces its entire weight with ATP
- At maximal exercise, a person creates 0.5-1.0kg of ATP per minute¹
Sooooo, it's a lot.
4 Main Functions of ATP
ATP is one of the busiest compounds in the human body. It is involved in a wide range of processes, making it crucial.
We'll go through some of these (we'd be here too long if we reviewed every process), but we'll start with the most essential part of the world of fitness and bodybuilding: its role in providing energy for muscle contractions. This is crucial!
1. ATP Powers Muscle Contractions
Yep! ATP powers every muscle contraction in the human body.² This is regulated by specific signaling pathways that vary depending on the type of muscle and its function. However, all contractions occur from ATP interacting with the proteins actin and myosin. Here is a brief rundown of what's happening:
- ATP binds to myosin
- ATP is hydrolyzed by ATPase into ADP and inorganic phosphate (It loses a phosphate)
- Myosin undergoes a conformational change that allows it to bind to actin
- Myosin, now attached to ADP and a phosphate, forms cross-bridges with actin
- ATP releases a phosphate, becoming ADP, which releases energy
- This energy drives the power strike, which causes the actin filament to slide past the myosin filament, leading to muscle contraction
- Another ATP molecule attaches to myosin, which releases it from actin
- A new cycle begins
Now, that's way more information than is absolutely necessary. However, it's still cool to know and see how complex a single muscle contraction is.
The bottom line is ATP is like a spark plug igniting every contraction.
2. ATP Is A Neurotransmitter
ATP is a neurotransmitter that facilitates communication between nerve cells (neurons). It can be released by both:
- Peripheral neurons
- Central nervous system (the brain and spinal cord)
As a neurotransmitter, ATP is necessary to maintain homeostasis (equilibrium) throughout the body and is also essential for synthesizing DNA and RNA.³
The triphosphate component of ATP is necessary for RNA production, while ATP is converted to deoxyribonucleotide (dATP) for DNA synthesis by removing an oxygen atom.
ATP is vital for intracellular signaling within cells. It helps release various messengers, including hormones, enzymes, lipid mediators, neurotransmitters, nitric oxide, growth factors, and reactive oxygen species, all of which regulate cellular functions.
3. Powers Metabolism
This is a bit like a catch-22 and demonstrates how crucial ATP is. As we mentioned above, with muscle contractions, ATP is the energy currency of the human body. It's necessary to power a host of processes, including metabolism.⁴ At the same time, we need our metabolism to resynthesize more ATP! This means that we need ATP to resynthesize ATP!
We'll go over these processes in more detail below, including the amount each metabolic system yields. However, keep in mind that each of those metabolic systems utilized ATP during the entire process!
With that said, some of these mechanisms include:
- Energy Source: When ATP releases a phosphate and releases energy, it fuels the metabolic processes (glycolysis and the citric acid cycle).
- Biosynthesis: ATP is required for the synthesis of various compounds such as proteins, nucleic acids, and lipids
- Regulation: High levels of ATP can signal the cell to conserve energy, while low levels can trigger pathways that generate more ATP.
- Transport: ATP is needed to power the transport of various compounds across membranes, helping maintain cellular homeostasis and some other metabolic functions.
Related: How To Get A Fast Metabolism
4. Improves Recovery
ATP is required to power the body's physiological systems and plays a role in recovery. For example, ATP is required for powering muscle repair and growth! In fact, this is true for all cells.
Some of the other mechanisms:
- Enhanced Energy Availability: ATP will help replenish energy stores more quickly, which can be transferred to increased recovery
- Reduced Muscle Fatigue: Higher levels of ATP can help the body maintain optimal energy levels, reducing the onset of fatigue.⁵
- Improved Blood Flow: ATP may promote vasodilation, improving blood circulation. This enhances the delivery of oxygen and nutrients to recovering muscles while aiding the removal of metabolic waste products.
- Inflammation Reduction: ATP might have anti-inflammatory properties, helping to decrease muscle soreness and inflammation post-exercise.
The Resynthesis Of ATP
You often hear about coffee giving us "energy," but caffeine is actually a stimulant; it's sort of like an artificial source of energy. Conversely, ATP is the true source of energy as it fuels the body's processes. In fact, it may be better to think of it as the body's fuel as this better describes its role.
The problem is that as ATP is used, it must be replaced! We're now going to look at how this occurs.
Resynthesis Of ATP (Metabolic Systems)
Once ATP loses a phosphate compound, it becomes an ADP or an adenosine diphosphate compound. Even though ADP has two phosphates, one is not able to break off to provide more energy. Therefore, more ATP must be resynthesized through one of three metabolic systems.⁶
These three systems are:
- Oxidative system (Aerobic)
- Glycolytic system (Anaerobic)
- Phosphagen or ATP-CP system (Anaerobic)
Oxidative System
Your oxidative system is your only aerobic metabolic system, meaning that it needs oxygen to resynthesize ATP. Therefore, it is the primary system responsible for synthesizing ATP during low-intensity activity of durations longer than 2:00.
It's the only metabolic system that can convert all 3 macronutrients into ATP, making it very efficient. To do this, the oxidative system includes various highly complicated processes, such as the Krebs cycle, to synthesize high yields of ATP from glucose. However, as it produces so much ATP slowly, the process takes much longer.
Just one glucose yields 38 ATP.
Your oxidative system supplies ATP for any activity longer than 2:00, such as:
- Running
- Cycling
- Swimming
Glycolytic System
The glycolytic system is the second of your two anaerobic systems. This means it doesn't need oxygen to synthesize ATP. Unlike the phosphagen system, the glycolytic system does resynthesize ATP from your macronutrients. However, it can only do so with carbohydrates.
This occurs when a molecule of glucose enters the cytoplasm and is synthesized into ATP.
Your glycolytic system is primarily used for intense activity from around 0:30 to 2:00. This means it needs to produce energy relatively quickly, and by doing so, it forfeits the large number of ATP that the oxidative system yields.
After the entire process, the glycolysis system only yields 2 ATP.
Your glycolytic system supplies ATP for activities such as:
- 200m sprint
- 100m swim
- Circuit training (if it's continuous)
Phosphagen System
Your phosphagen system is the first metabolic system and is anaerobic in nature. This means it doesn't need oxygen to replenish ATP. In fact, it doesn't even need one of your macronutrients!
It uses a compound known as creatine phosphate. Yes, that creatine (we'll talk about creatine supplementation below!).
Your phosphagen system helps to resynthesize ATP during high-intensity events of 30 seconds or less. This means it needs to supply energy fast, real fast.
It uses a one-step process to do this. Remember that ATP becomes ADP after it donates phosphagen.
- ATP → ADP + Energy
This means it needs another phosphagen to become ATP again. When needed, creatine phosphate (which is stored in your muscles) is released. It then donates its phosphate molecule to ADP, creating another molecule of ATP.
- ADP + CP → ATP
There are plenty of other metabolites involved, but that reaction demonstrates the general idea.
Creatine Supplementation And ATP
We just discussed the phosphagen system above, so you already know that creatine is related to ATP. Therefore, we want to discuss creatine supplementation.
Unless you've been living under a rock, you at least know what creatine supplements are, and there's a good chance you take them. You probably also know they're considered the most effective supplement on the market.
This is why.
Our body's natural creatine stores are finite and controlled by two mechanisms:
- Our diet
- Natural synthesis internally
When accounting for the differences in everyone's natural creatine stores, we find that, on average, our stores are only 60-80% full. Therefore, we fill these stores to 100% by supplementing with creatine. Upon consumption, creatine goes through a phosphorylation process, where a phosphate compound is added and stored as creatine phosphate.
Then, when we go to the gym, our body can produce more ATP. This extra ATP then helps us to produce more energy to:
- Lift a heavier load
- Perform more reps
- Increase total work volume
All of this, over time, leads to strength and muscle mass gains.
Can You Supplement With ATP?
Yep!
Various studies have demonstrated that supplementing directly with oral ATP can improve anaerobic performance. For example, a large meta concluded that supplementing with 400mg of ATP daily can increase maximal strength in trained adults.⁷
There are fewer studies on aerobic performance, but this makes sense. Remember that your body already makes large amounts of ATP aerobically. On the other hand, during anaerobic exercise, less ATP is produced, so having that extra supplementation would be more beneficial, theoretically.
Final Say On ATP
ATP may be the most important compound concerning performance. It fuels every rep you lift and every breath you take. Without it, we simply wouldn't function. The good thing is our body is extremely effective in maintaining our supplies. However, you could increase your ATP stores through supplementation, as we spoke about, or just be sure to follow a healthy diet. Also, be sure you train all your metabolic systems to ensure you always have enough ATP!
Now that you know about ATP you should check out our post covering V02 Max to level up your training!
References
- Pizzorno, Joseph. “Mitochondria—Fundamental to Life and Health.” Integrative Medicine: A Clinician’s Journal, vol. 13, no. 2, Apr. 2014, p. 8, pmc.ncbi.nlm.nih.gov/articles/PMC4684129/.
- González-Marenco, Roberto, et al. “The Effect of Oral Adenosine Triphosphate (ATP) Supplementation on Anaerobic Exercise in Healthy Resistance-Trained Individuals: A Systematic Review and Meta-Analysis.” Sports, vol. 12, no. 3, 1 Mar. 2024, p. 82, www.mdpi.com/2075-4663/12/3/82, https://doi.org/10.3390/sports12030082. Accessed 3 Apr. 2024.
- Rizo, Josep. “Molecular Mechanisms Underlying Neurotransmitter Release.” Annual Review of Biophysics, vol. 51, 9 May 2022, pp. 377–408, pubmed.ncbi.nlm.nih.gov/35167762/, https://doi.org/10.1146/annurev-biophys-111821-104732.
- Lancaster, Gemma, et al. “Modelling Chronotaxicity of Cellular Energy Metabolism to Facilitate the Identification of Altered Metabolic States.” Scientific Reports, vol. 6, no. 1, 3 Aug. 2016, https://doi.org/10.1038/srep29584. Accessed 4 Apr. 2024.
- González-Marenco, Roberto, et al. “The Effect of Oral Adenosine Triphosphate (ATP) Supplementation on Anaerobic Exercise in Healthy Resistance-Trained Individuals: A Systematic Review and Meta-Analysis.” Sports, vol. 12, no. 3, 1 Mar. 2024, p. 82, www.mdpi.com/2075-4663/12/3/82, https://doi.org/10.3390/sports12030082. Accessed 3 Apr. 2024.
- Alger, Angela Harter. “8.3 Phosphagen System (ATP-CP System).” Pressbooks.calstate.edu, vol. 8.3, 2022, pressbooks.calstate.edu/nutritionandfitness/chapter/8-2-phosphagen-system-atp-cp-system/.
- González-Marenco, Roberto, et al. “The Effect of Oral Adenosine Triphosphate (ATP) Supplementation on Anaerobic Exercise in Healthy Resistance-Trained Individuals: A Systematic Review and Meta-Analysis.” Sports, vol. 12, no. 3, 1 Mar. 2024, p. 82, www.mdpi.com/2075-4663/12/3/82, https://doi.org/10.3390/sports12030082.
Garett Reid
Author