I am at the lowest healthy BMI so I don't want to lose weight however my underarms and back are decidedly flabby. I size the back size of my bra generously (old fashioned method not not boob or bust) as I have had a mastectomy and hate anything pressing on scars. The cups of my bras fit - any bigger and they wrinkle. I run and do a few weight and resistance exercises. I was just wondering whether there were any exercises people had noticed a real difference with on their laterals (think this is the correct muscle). I'm sure bra fitting would be much easier if these muscles were firmer.