Dive Brief:

• Nike on Wednesday filed suit against Lululemon, specifically its Mirror home gym division and accompanying mobile apps, claiming it infringed on patents the athletics giant has filed over the years. 
• Among other things, Nike claims in the lawsuit that Mirror's system infringes on a patent it filed for an apparatus that prompts users to reach certain exertion levels and determines heart rate zones based on real-time measurements.
• "The patents in question are overly broad and invalid," a company spokesperson for Lululemon told Retail Dive via email. "We are confident in our position and look forward to defending it in court." Nike did not immediately respond to a request for further comment on the lawsuit.

Dive Insight:

As athletics retailers get more involved in connected fitness, Nike is taking aim at Lululemon's relatively recent Mirror acquisition for infringing on its patents.

In a letter sent to Lululemon prior to filing the lawsuit, Nike outlined six patents it claims Lululemon is infringing on, with the aim of coming to an "amicable resolution." Lululemon in December replied that it did not think Mirror infringed on those patents and less than a month later Nike filed its suit.

Mirror's "Face off" feature, which allows users to compete against each other in workouts, is also under attack by Nike, which cited a patent it has for a workout method that includes one user competing in an athletic challenge against a second user and determining the athletic activity of both users from sensor data.

In its lawsuit, Nike said it "has suffered, and continues to suffer, economic harm as a result of Lululemon's infringing activities" and that Lululemon's actions have caused "irreparable injury." Nike is asking the court to prevent Lululemon from infringing on its patents going forward, as well as for Lululemon to pay damages to Nike, including its attorneys' fees.

Mirror hasn't been a part of Lululemon for long, but it has already brought some challenges to the retailer. Generally a favorite with analysts, Lululemon has been questioned on Mirror's growth and profitability over the past year and a half, and the retailer has given little away about the performance of the business. In September, just before the startup's CEO stepped down, Lululemon acknowledged Mirror was not profitable but declined to share a path to profitability.

"In our view, given limited disclosure, the Mirror acquisition has seemingly introduced noise into an otherwise clean equity story," Morgan Stanley analysts led by Kimberly Greenberger said in emailed comments at the time.

In addition to its court battle with Nike, Lululemon is also fighting Peloton over apparel designs that Lululemon claims Peloton copied. The lawsuit came shortly after Peloton released its own apparel line; the company had partnered with Lululemon on apparel in the past.