I have been buying this sports bra for about 12 years now, maybe a little longer.  I'm a 34GG and I use the 34DD size and my girls don't move.  I can go for a run, do a class, or play sports and I'm not concerned about being all over the place an uncomfortable.  Both the straps and the back adjust just like a regular bra.  I work out 5 days a week and play sports and each of these will last me around a year.  If you're looking for maximum support and comfort this is it!