Given a scientific question, generate a correct answer to it.

Input: Consider Input: What works by providing a lower energy pathway from reactants to products?

Output: catalyst

Input: Consider Input: What type of fibers are made mostly of protein in living things?

Output: muscle fibers

Input: Consider Input: When it was found that, without the force of gravity exerting pressure on the bones, bone mass was lost in astronauts, what kind of exercise provided an antidote?
Output: resistive