Athletic breasts are small but wide, and feel firmer as opposed to squishy. Athletic shaped breasts feel firmer than most because they have a higher muscle to fat ratio, and because of this they often tend to be on the smaller side and don't require a lot of support.
Styles to try:
Wire-free / Soft Cup or Bralette
An easy-to-wear comfortable style that also offers lightweight support. The under-band of this style provides comfortable, soft, and stretchy support to the often-larger under-bust that accompanies Athletic shaped breasts. Demi /Balconette. The horizontally cut cups, meaning this bra is less likely to gape on smaller more muscular breasts. In addition, a Demi / Balconette style also lifts the breasts to enhance the natural shape, creating a rounder and fuller look.