Is it the anatomical cross-section, physiologic cross-section, average muscle fiber Length, or muscle volume.

If you know that a single motor cell contraction is an all-or-nothing phenomenon, it is understandable that the force exerted is proportional to the amount of fibres that do contract. Which one of the answers is most closely related to the amount of fibres?

I would say physiologic cross section then. I just wonder between that and muscle volume. But volume isn't more closely related I guess.

That's what I'd answer, though the difference between anatomical and physiological cross-section is not entirely clear to me.

 

Volume, indeed: no. The only thing that differs cross-section from volume, is length. The length of a fibre and, by extension, its sarcomeres, does indeed determine the contractility of one fibre. But as mentioned before, once contracted, it's contracted. It can't be semi-contracted or contracted for 90%, 50%, ...

Thanks a lot for your input!