Something that's cropped up a lot with clients lately is 'getting rid of bingo wings'. I get it, flappy skin isn't ideal, but here's the bad news - there's not loads you can do about it. Yes, we can work to build up our triceps and have truly boss arms, but if the muscle is relaxed (which it will be when your arm is in 'waving' position), it'll still wobble a bit.
Then there's age. From about 36, women's oestrogen starts to decline, and with it the elasticity (collagen) in our skin. There is little to no evidence that collagen supplements work, or skin firming cream or really any other fixes on the market. It's just what happens.
And then there's genetics. So you might get to 80 and never have bingo wings because your particular genetic make-up means you don't sag in those places. Another thing you can't influence.
There is a LOT of waving at the start of the Barbie movie. And although it is stylised and doll-like, there's definite wobble in ALL the immaculate women's arms. I've seen the movie twice so can be trusted on this.
I think the best approach is to work on building a strong body and being happy with what you have. And if you're really worried, maybe consider a jaunty salute when you next spot a friend across the street.