Guinea pig questions

If someone demographically normal and not especially at-risk wants to serve as a guinea pig, what is the optimal allocation of that resource?

Is there any formal discussion of this question? I know they say “there is always an Effective Altruism blog post,” but is there?

Mostly I have medicine and medical experimentation in mind, but I can imagine other answers as well, such as “trying to leap forty flaming cars with a motorcycle.”  Though I doubt that one will end up as the winner.  In any case, I am assuming away legal constraints.  Where can you volunteer as a guinea pig for the highest social value?