Fantastic art!! One of the best Tigra's I have seen. I think the whole flattening out due to gravity would lessen the effect and some people just plain out have extra tone (if superheroines aren't in top shape then who is, lol). Great stuff!!
They don't seem too off, besides you worked out the body pretty good here, there can't be that much wrong with it can there?
Hell look at Starfire from Teen Titans for more proof. ^o^
Not to mention sexier. Seriously out all the hotties in the world its often you hear alot or see alot of people drawing them. Good you went with the red though, its detail would have been somewhat lost if you chose to stick with a less colorful tone like brown.
Very pretty face and coloring. She seems in a stiff posture, the way she is lying on the ground. Her thighs and backside would flatten out more, unless she is flexing her muscles. Got a large mirror at home? Muscles are muscles whether male or female and will pretty much behave the same way. Lay down in the same posture and relax, you'll see that you do flatten out.
It's too bad that you couldn't do her feet, that would have made for a very nice full length illustration.