Final answer:
The energy system primarily developed by work relief, such as in sprinting, is anaerobic. This system includes both the alactic and glycolytic pathways and uses glycogen as an energy source, with ATP being the primary molecule utilized during muscle contractions.
Step-by-step explanation:
The energy system that is primarily developed by work relief, such as activities involving short bursts of high intensity, is anaerobic. This type of metabolism becomes predominant in sprinters, where they perform at high intensities for a short duration, relying on energy systems that do not require oxygen. In contrast, aerobic metabolism is more developed by exercises like marathon running, which require sustained energy over a long period. Within anaerobic metabolism, there are two main pathways: the alactic system, which utilizes phosphocreatine and does not produce lactic acid, and the glycolytic system, which breaks down carbohydrates to produce energy and can lead to the accumulation of lactic acid when oxygen is scarce. Glycolysis can occur in both aerobic and anaerobic conditions, but it is part of the anaerobic glycolytic system during high-intensity, short-duration exercises like sprinting.
In the context of muscle metabolism, anaerobic activities use glycogen as an energy source, whereas aerobic activities can utilize fatty acids, glucose, and glycogen in the presence of oxygen. When the cells perform work, such as during muscle contraction, they use ATP (adenosine triphosphate) as the primary molecule to store and transfer energy. Glycolysis is especially important because it is a metabolic pathway that can function both with or without oxygen (anaerobically or aerobically) and is found in all domains of life, indicating its primitive origin. Furthermore, when muscles undergo intense exertion, such as during sprinting, they can perform lactic acid fermentation to rapidly regenerate ATP from ADP and sustain muscle contraction.