The Under Armour logo uses a variety of Gestalt Principles including: similarity, proximity, and closure. All of these elements combine to make the Under Armour logo so clever, unique and memorable.
Traditionally, the entire Under Armour logo is black. I say traditionally because now the logo can appear in many different colors on sweatshirts, sneakers, pants, etc. However, the logo, no matter what, is a solid color. This consistency, or similarity, is an important part of the logo. Because the color is solid, a person is able to see both the “U” and the “A” within the logo that represent Under Armour. Also, solid colors are bold. Boldness is often a trait of a successful athlete. Since Under Armour is used by athletes, the color is suitable.
Proximity is also used in the Under Armour logo. The overlap of the arches are used to create the “U” and the “A” of Under Armour. What makes the Under Armour unique is this overlap. If the logo was simply the two letters next to each other, the logo would be less unique and therefore, less memorable.
Finally, the Under Armour logo also uses closure. By mentally connecting the lines both at the top and the bottom of the logo, a person will see that the logo is a shield. Under Armour has “Armour” in the name (obviously). This is because Under Armour is the apparel athletes wear when they are “heading for battle,” or a competition. A shield is a form of what we think of as traditional armour. Also, shields are strong in the way that athletes are.
Therefore, just by looking at the logo, a person can see that Under Armour products are associated with boldness, strength and competition.