Club Pilates retains its spot at the top of this year’s Fast & Serious list, but Urban Air Adventure Parks is nipping at its heels as that brand debuts on our ranking at No. 2. An investment from MPK Equity Partners in 2018 is helping fuel Urban Air’s rapid expansion, says CEO Michael Browning, who co-founded the franchise in 2011 and touts “revolutionary” initiatives such as a membership program for driving sales. Some franchisees have a different view, but the brand grew systemwide sales by nearly 293 percent over three years, to $216 million in 2019. Read more from Browning and check out strategies from the other 39 companies on this list in our exclusive research project that identifies sustainably growing brands.