Final answer:
During muscle work, chemical energy is converted to mechanical energy, with the excess energy primarily released as heat.
Step-by-step explanation:
Conversion of Chemical Energy in Muscles
When muscles are at work, they convert chemical energy to mechanical energy. However, this process is not perfectly efficient; only about 20-25% of the chemical energy is used for mechanical work such as lifting, moving, or digging. The remaining energy is primarily released as heat, which helps to maintain the body's temperature.
This heat generation is a result of the body's metabolic processes, where the catabolism of food releases energy that was temporarily stored in ATP (adenosine triphosphate), fueling muscle contraction and other energy-demanding activities. Indeed, in all energy transformations within the body—and as per the conservation of energy—chemical energy is converted into other forms, with heat being the most common byproduct.
Therefore, when muscles work and convert chemical energy to mechanical energy, the correct answer to what else is released during this process is Option 1: Heat.