US-based Franchise-based health club chain Orangetheory Fitness has opened its 500th studio in Seattle-Ballard, Washington, US.

The opening is part of the company’s explosive growth in the US, which has seen a 69 per cent increase in studio openings in 2016 from the same time last year.

As part of its plans to further strengthen its brand recognition, Orangetheory is also bringing in Fox Sports broadcaster and Dancing With The Stars television host, Erin Andrews, on board as its new brand ambassador.

Andrews will help launch the company's 2017 marketing campaign "There is no after," which aims to highlight the company’s USP – the “science” behind its workouts – and how its members are never simply done with a workout but in a “constant state of improvement”. The campaign kicks off on 1 January 2017.

Orangetheory launched its first studio in Florida in March 2010 and has since become one of the world's largest fitness franchises, with 500 studios in seven countries – the US, Canada, the UK, Australia, Mexico, Dominican Republic and Colombia.

Dave Long, co-founder and CEO of Orangetheory Fitness said: "We knew when we opened our first studio six years ago that we were onto something.

"But what we've experienced with Orangetheory Fitness has simply blown me away. We're excited to celebrate what we've accomplished thus far, but are continuing to plan for an even more successful future. Trust me when I say, we are just getting started."

According to Long, the company is on track to have 700 studios by 2017.

The Orangetheory concept is based on 60-minute, five zone heart-rate monitored interval training designed to help members meet their individual fitness goals in a short amount of time.