A day after posting its highest quarterly earnings ever, adidas is attributing its turnaround in America to a surge in running sneaker sales and more specifically, the Ultra Boost.

adidas Group North America president Mark King told Fortune that North American sneaker sales jumped 54 percent last quarter alone, with the biggest push coming from the brand's running category, which increased by 30 percent. The only sneaker that King calls out by name is the Ultra Boost, which he notes was an "especially strong" performer. "Success starts from the feet up," King said.

Although adidas controls a smaller portion of the market, Fortune adds that data from the NPD Group shows that the Three Stripes' running division is growing at a faster rate than Nike and Under Armour's departments. In fact, adidas' sales as a whole are increasing faster than Nike's right now. 

Collaborations with Kanye West and Pharrell Williams have proved to be worthwhile for the brand, too. Although these limited edition projects don't move big numbers, they help contribute to the "cool" factor that adidas has been seemingly lacking in recent years. 

The reason that North American success is so important for adidas is because it wasn't long ago that the brand was actually experiencing a decrease in sales. In 2014, revenue in North America dropped by 20 percent, and adidas has been trying to turn things around ever since. Now, with sneakers like the Ultra Boost, it looks like the brand has finally figured it out