Q: This is about Kuzuki-sensei who is physically stronger than regular people. Aside from his fists being strengthened by Caster, are the rest his own strength, or did Caster strengthened other parts of his body as well? <Soujuurou of the Hill>

Nasu: In the anime version, his entire body is strengthened. When the excessively worrying Caster buffed him to ten times that of a normal human, since Kuzuki's base strength is higher than a normal human, he became even more ridiculous, and did the unthinkable during his fight with Saber. Caster was surprised herself: "What the? Isn't my Master a little too strong?!"
Takeuchi: On a side note, it was also thanks to Caster's help that Kuzuki was able to move inside to Rider barrier.

Fate/Stay Night Animation Material I; Q&A, pg. 42