Like Shawn, I see no need for a mixed model (aka multilevel model). There's no reaon your errors should not be independent in the "regular" regression and that is the problem that MLM or mixed models are designed to solve.

But I would include an interaction between sex and Gatorade. It seems to me that what is interesting here is whether Gatorade has different effects on the runtime of men and women, and that is what an interaction tests.

Like Shawn, I see no need for a mixed model (aka multilevel model). There's no reason your errors should not be independent in the "regular" regression and that is the problem that MLM or mixed models are designed to solve.

But I would include an interaction between sex and Gatorade. It seems to me that what is interesting here is whether Gatorade has different effects on the runtime of men and women, and that is what an interaction tests.