Helen Parr aka. Elastigirl has the power to bend and change her shape, so is she choosing that shape or is that just the way she is?
21I mean, the very screenshot you've used for illustration should be evidence enough that she cannot change shape at will at no cost - she's disappointed about her "natural shape". Why would she if that weren't her natural shape? Disappointed at not even trying anymore? :)– LuaanNov 25, 2020 at 16:26
Aside from the reason stated in the other answer of her needing force/to concentrate to be stretching we can also infer it’s her natural state from another reason. Every time we see her unstretch she returns to her normal state by snapping back into it. To me this indicates that the usual state we see her in is her natural form. We see it happen a couple of times in the scene below:
The image provided with the question looks to supply the answer.
In that scene, Elastigirl appears not entirely happy with her shape in the new skintight costume. (It's been a few years and three children since her last outing in a hero suit!)
If Helen Parr could adjust her figure at whim, that scene would show her butt inflating and deflating until she found the size that pleased her.
3I actually thought about putting this point in my answer but decided it was a little too weird Nov 25, 2020 at 18:11
Superpowers usually require some level of focus and concentration to use. You have to decide exactly how much strength you want to use or you have to decide to "kick in" your super speed. The concept is similar to elastic powers.
Notice the keyword "elastic" that says what she is doing is stretching. So that requires her to decide how much and what she stretches. If this weren't her natural shape, we would be seeing her change back to what is her natural shape occasionally, which we don't.
So the conclusion is that, yes that is her natural shape.
5A few quotes from the movie or related sources would help your answer. Right now, it looks like speculation. If you provide quotes, I would upvote it.– user89104Nov 25, 2020 at 4:08
11@LincolnMan Evidence doesn't have to be in the form of quotes; reasonable logical deduction can also be the basis for a good answer. Not everything without quotes is just speculation.– Rand al'Thor ♦Nov 25, 2020 at 7:24
5Everything you said is true of standing up, too– ikegamiNov 25, 2020 at 9:08
2@ikegami if you have to concentrate in order to stand up stop drinking or see a doctor as appropriate. Nov 27, 2020 at 11:05
2@PeteKirkham Ever been told since bad news? The point is, we're capable of devoting certain amount of effort without even realizing it. And you're proving it.– ikegamiNov 27, 2020 at 11:31