Castanea Partners has purchased a minority interest in Fitness Anywhere, LLC of San Francisco, which develops and markets suspension training equipment and content under the TRX brand.

The California company was founded by a former US Navy SEAL in 2004 as the commercial platform for a training technique he invented to help Navy SEALs without access to gyms or safe outdoor space maintain high levels of strength and conditioning.

“We're very excited about partnering with Fitness Anywhere,” said Brian Knez, Managing Partner of Castanea, in a statement. “Suspension training is a valid training regimen with tremendous performance benefits that has created a high level of enthusiasm and advocacy among trainers, professionals, and recreational athletes.”