Peloton Interactive on October 15 was sued for patent infringement by Icon Health & Fitness, the maker of the NordicTrack bike, escalating the legal tussle between the two fitness equipment giants.

Logan, Utah-based Icon filed a lawsuit in a Delaware district court that is built around patent infringement claims for two features Peloton added to an exercise bike released in September: a swiveling touchscreen and the ability for the bike to automatically change resistance levels during classes.

In the lawsuit, Icon claims that it was issued a patent for the resistance level feature, which Peloton calls Auto-Follow, in 2007 and a second issued last year that allows for a seamless mix of aerobic and anaerobic exercise. Both are part of the Bike+, Peloton’s latest offering, and are also present across several of Icon’s NordicTrack products.

“Some companies, like Peloton, have built (at least in part) entire businesses on the back of Icon’s patented technology,” the filing claimed.

Peloton shares dropped by 3.7% when markets opened October 15 and were trading down 0.7% at $130.54 at 9:59 a.m. in New York.

The two companies have crossed swords before. New York-based Peloton sued Icon in May, claiming that the company copied its patented feature for making prerecorded online classes seem live. Peloton said at the time that Icon “attempted to free ride off Peloton’s innovative technology.” Icon had previously sued Peloton when its first bike was launched and again when Peloton launched its first treadmill.

In October 15’s lawsuit, Icon fired back by saying it obtained “hundreds of patents on these systems before Peloton was founded.” It said that Peloton Chief Executive Officer John Foley met with Icon in 2013 in an attempt to use some of its patents and that Icon declined the opportunity to grant him a license.

“Foley was warned at that meeting and subsequent meetings against infringing Icon’s patents,” according to the lawsuit.

The latest development in the Peloton and Icon saga comes amid major growth in the home fitness market, as consumers looked for ways to stay fit with many gyms across the U.S. remaining closed due to the COVID-19 pandemic. Icon reached a $7 billion valuation in a new funding round, Bloomberg News reported earlier this month.

In its latest lawsuit, Icon is seeking unspecified damages and an injunction against sales.