Q: exersize for flabby under arms

A: The extra flab is plain old fat and possibly some loose skin (if you had a large weight loss already). Unfortunately you can't spot reduce, meaning you can't target fat loss in just one area such as back of your arms. You also can't do a whole lot for loose skin short of surgery. Applying vitamin E creams may help slightly.

The main thing you'll have to do to reduce the flab is simply lose fat overall. If you lose fat overall, you'll lose it on the back of your arms too. Please read this carefully and read the other two articles it references. It will tell you exactly how to go about losing fat in the most efficient way. Even though it may not be the fast-acting magic bullet against backarm flab that you were hoping for, it IS the best way to go about it. It will also benefit you in the long run in countless other ways.

There's also a chance that building up tricep muscles will mask the flabbiness a little bit and weight training will help with that. By following the programs described in the articles I pointed you to, you'll accomplish that as well. Good luck!