Alongside sneakers, gym shorts, and yoga pants, sportswear brands are adding one more must-have to their list of products: workout apps.

Unlike Nike Inc., which has been developing its own running and sports apps for years, rivals have taken to acquiring startups to stay relevant among gym rats who want to quantify their every step, jump, and calorie burned. The latest is Asics Corp., the Japanese apparel maker that said it acquired Runkeeper last week for $85 million.

Under Armour Inc. kicked off the buyout frenzy in 2013, when it spent $150 million for MapMyFitness. Then in February 2015, Under Armour said it bought Endomondo for $85 million and MyFitnessPal for $475 million. Adidas AG snapped up Runtastic in August, giving the software company an enterprise value of 220 million euros ($239 million).