Final answer:
A resting muscle obtains most of its energy needs from aerobic respiration. Approximately 95 percent of the ATP required for resting or moderately active muscles is provided by aerobic respiration in mitochondria. Creatine phosphate and glycogen are also used as energy sources, but they are not as efficient as aerobic respiration.
Step-by-step explanation:
A resting muscle obtains most of its energy needs from aerobic respiration. Approximately 95 percent of the ATP required for resting or moderately active muscles is provided by aerobic respiration, which takes place in mitochondria.
During aerobic respiration, glucose is broken down in the presence of oxygen to produce carbon dioxide, water, and ATP. This process is more efficient and produces a larger amount of ATP compared to other energy sources like creatine phosphate and glycogen.
Creatine phosphate can supply energy to a working muscle at a very high rate, but only for about 8-10 seconds. Glycogen is another energy source that can be used to make ATP from glucose, but it is slower compared to creatine phosphate. During intense exercise, when oxygen cannot be sufficiently delivered to the muscles, pyruvic acid is converted to lactic acid, which may contribute to muscle fatigue.