Final answer:
Energy for developing muscular fitness comes from the metabolism of glucose, fructose, or galactose. ATP, the energy currency of cells, is synthesized through metabolic reactions.
Step-by-step explanation:
The energy needed for developing muscular fitness comes from the metabolism of glucose, fructose, or galactose. ATP, which is the energy currency of cells, is synthesized through metabolic reactions that produce ATP. These reactions rely on the chemical energy stored in the bonds of organic molecules found in food. This metabolic process converts the chemical energy stored in food into adenosine triphosphate (ATP), which is used by cells as a direct energy source. While the efficiency of energy conversion is about 20-25%, resulting in the majority being released as heat, the energy that drives the synthesis of ATP and fuels muscular fitness activities comes from the breakdown of glucose. The glucose molecule, with the chemical formula C6H12O6, is metabolized through catabolic reactions, producing ATP in a form that can immediately be used by the cells for different functions including muscle contraction, which is crucial for muscular fitness.