If supercharging herself makes her like captain america, then I think she should be fine jumping out of a three story window, albeit with a very high chance of some ankle injury.

Also, training your body definitely makes it more durable. Injury on the other hand always makes the body weaker. Thats why Batman is so ridiculously implausible: the amount of hits he's taken over his career aren't things that go away over time; they stay with you for life.

Of course, if you throw regeneration into the mix, then it may well be a different story.

By the way, there is a person who can turn into a ridiculously fast monster when no one is looking at her. Her weakness is that no one can look at her, but what are the weaknesses of the monster? How does that monster even operate at such high speeds? Wouldn't the friction of the air be a major factor in how it moved? How would the air behave to having it run running through it? Would there be a sonic boom?

I agree that it is unfair to scrutinise he pseudo-science for some characters and not for others.