Energy Systems Used During Exercise
Immediate source of energy
The body energy systems are understood by few and can leave people confused. Open a quality personal training textbook and it can leave you scratching your head when reading about aerobic, anaerobic, and immediate metabolism.
Most people want to know; What is the immediate source of energy for all cellular activities, including muscle contraction? The short answer is Adenosine Triphosphate (ATP).
The reaction that makes ATP into energy is complex, however here is a brief explanation of how it works. Adenosine Triphosphate (ATP) is an adenine nucleotide bound to three phosphates. There is a substantial amount of energy stored in the bond between the second and third phosphate groups that is spent to fuel chemical reactions in the body.
When our cells need energy, our system breaks these bonds to form adenosine diphosphate (ADP) and a free phosphate molecule. When our cells have excess energy, it creates ATP from ADP and phosphate. ATP is needed for the biological responses involved in all muscle contractions.
As the workload on the muscles increase, more ATP gets used and must be replenished for the muscle to continue to be in motion.
The following are frequently asked questions quick, with quick concise answers:
What are the three energy systems that make ATP?
- ATP-CP (Phosphagen) System
- Anaerobic Glycolysis (Lactic Acid) System
- Oxidative System
a. Aerobic Glycolysis
What are the three types of macronutrients utilized for the production of ATP during the oxidative system?
- Fats (Lipids)
How long can the ATP-CP (Phosphagen) system provide energy to the working muscles? 10-30 seconds during exercise with all-out effort.
How long can an exercise be sustained utilizing the Anaerobic Glycolytic system? 30 seconds to 2 minutes
How long can Aerobic Glycolysis provide enough ATP to fuel the body? 4 to 20 minutes of intense activity.
Beta-oxidation occurs when fats are used for energy. Glycogen in the muscle and liver is quickly used during intense exercise. The body will use fat for energy to conserve its store’s glycogen. The body begins to use fats for ATP production during exercise that lasts longer than 20 minutes.
Protein plays a minor role during exercise because it is not readily broken down for energy.
So what would that all look like if we are out doing exercise? Well if you were out running this is what would happen in your body. The muscle cells burn off ATP they have hanging around after about 3 seconds. Then your phosphagen system reacts to supply further energy for 8 to 10 seconds. The phosphagen system is the main system used by the muscles of a 100-meter sprint or lifting weights, or when quick acceleration, brief-duration activity happens. However, when activity continues, the glycogen-lactic acid system starts to kick in. This would be the case for exercises such as a 200-400 runs or a 100-meter swim. Last but not least; aerobic respiration begins to take over. Endurance events such as the an 800-meter run, marathon run, cross-country skiing would be good examples of where aerobic respiration comes into play.
Carbohydrate Fueling Prior to Exercise to Ensure Top Sports Performance
When competing in sports events, endurance athletes, use carbohydrates as their primary fuel source. It is most beneficial to consume whole grain, complex carbohydrates about 3 hours before working out or competing. It is not recommended to eat high glycemic carbohydrates before exercise because it results in a quick release of insulin and reduced blood sugars, suppresses the release of fatty acids from the fat stores and inhibits liver glycogen breakdown.
How much Do I Need Before and After Exercise?
During intense exercise, you should be averaging 25–30 gm/30 minutes of activity. Ensure any carbohydrate drinks do not exceed 6 – 8 % of the total serving. Concentration levels that are too high can result in cramps, nausea, and diarrhea.
After intense exercise, it is important to restore muscle glycogen by eating a mix of carbohydrates with a small serving of protein. Simple carbs are best to restore levels quickly. Do not over fuel at this point; many people end up gaining weight by consuming too much after exercise.
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