For his latest Olympic journey, Michael Phelps is bringing along a special pair of Under Armour's new training shoe, the Architech.
The shoes are noteworthy because the mid-sole is created by 3D printing technology. Under Armour quickly sold out of a limited edition version of the 3D-printed sneaker in March.
Phelps' shoe is special for another reason -- clearly visible on the inside is a tiny black footprint. It's from the foot of Boomer Phelps, the swimming champion's son, who will turn 3 months old when the games open Friday in Rio de Janeiro.
The small print on the big shoe is "a personal reminder that Boomer is with him every step and stroke of the way," Under Armour said in a release Tuesday.
Boomer Robert Phelps was born in May to the Olympian's fiancee, Nicole Johnson.
Long an Under Armour representative, Phelps is among the first to wear the Architech. In 3D printing technology, powder is heated by a laser, which is shaped and solidified. The technology holds the promise of one day designing form-fitting shoes for each consumer's feet.
Under Armour says a new color of the Architech will be available as a limited edition in August on the company's website and at its Brand House stores.