Final answer:
The subject and action of the sentence are 'Herr was climbing,' which tells us who is doing the action and what action is being performed. The timing of the action is indicated by 'while testing out the new designs.' The comparison in the sentence is found within 'Herr was climbing better and faster'.
Step-by-step explanation:
The subject and action of the sentence 'In fact, while testing out the new designs, Herr was climbing better and faster in his prosthetics than he ever had with his biological legs.' are expressed in the part 'Herr was climbing.' Here, 'Herr' is the noun that acts as the subject, and 'was climbing' is the verb phrase that describes the action he is performing.
The part 'while testing out the new designs' indicates when the action took place, acting as a time modifier in the sentence. It sets the context for when Herr was climbing better and faster.
A comparison is made in the part 'Herr was climbing better and faster'. It compares Herr's climbing ability in his prosthetics to his previous ability with his biological legs