Medical expert of the article
New publications
The importance of energy for anaerobic and aerobic physical activity
Last reviewed: 08.07.2025
All iLive content is medically reviewed or fact checked to ensure as much factual accuracy as possible.
We have strict sourcing guidelines and only link to reputable media sites, academic research institutions and, whenever possible, medically peer reviewed studies. Note that the numbers in parentheses ([1], [2], etc.) are clickable links to these studies.
If you feel that any of our content is inaccurate, out-of-date, or otherwise questionable, please select it and press Ctrl + Enter.
The energy that powers exercise and activity is generated by chemical bonds in food. The pathways for storing and distributing energy in the body are numerous and varied. Energy powers cell activity and muscle fiber contraction. Exercise performance, based on factors such as muscle fiber contraction rate, depends on the availability of energy in the muscle fibers, so energy conservation and transfer are critical factors in exercise performance. These processes are dependent on nutrient intake, fitness, genetics, and the type of exercise performed. Knowledge of these processes and the factors that influence them is essential for developing customized diets and training programs to optimize exercise performance and overall health.
Energy accumulation
Energy is accumulated in the chemical bonds of carbohydrates, fats or proteins. However, the chemical energy of proteins as a source of physical activity is not used immediately. The primary suppliers of chemical bond energy are fats and carbohydrates. Dietary fats are converted into fatty acids and used by the body. They can be used in various synthesis processes or directly as a source of energy. Excess fatty acids are converted into triglycerides and accumulate mainly in fat and, partially, in muscle tissue. There are no limits to fat accumulation, so the level of accumulated fat in people is very different. Fat reserves are 100 times or more greater than the energy reserves of carbohydrates.
Dietary carbohydrates are converted into glucose and other simple sugars and used by the body. Simple sugars are converted into glucose, which can be used in synthesis processes and as a source of energy. Excess glucose molecules are then incorporated into long chains of glycogen and stored in the liver and muscle tissue. The amount of glycogen that can be stored is approximately 100 g in the liver and 375 g in the muscles of adults. Aerobic exercise can increase the level of muscle glycogen storage by 5 times. Excess dietary carbohydrates consumed in excess of the level required to maximally fill potential glycogen depots are converted into fatty acids and stored in adipose tissue.
Compared to any carbohydrate or protein, fats more than double the amount of energy measured in kilocalories, so they are an effective means of storing energy while minimizing body weight. The energy in stored fat or glycogen is stored in the chemical bonds of these substances.
Another form of energy storage that comes directly from the chemical bonds of food products and is used to maintain motor activity is creatine phosphate (CrP), or phosphocreatine. The body synthesizes phosphocreatine and stores small amounts in the muscles. Creatine supplements significantly increase intramuscular levels of creatine and phosphocreatine.