diane macedo. >> one more time. we go in three, we go in two, we go right now. jumping jacksont's the fitness craze sweeping the nation. >> it makes you like super confident. >> you feel kind of invincible. >> reporter: the original high speed and hard-core workout once considered a man's sport is fast catching on as the hottest way for women to get fighting fit. everyone from celebrities to super models are stepping into the ring. >> it's fun especially whether when you're like really pissed at someone. >> reporter: kendall jenner, adrian nan lina and gisele sharing their boxing workout social media. here's gigi hadid showing off her boxing skills for reebok. new boxing gyms are opening all over the country and in new york city, models and mortals alike flock here to rumble boxing, a new fitness studio backed by rocky himself. >> rocky's coming back now. rocky's got him on the ropes. >> models like gisele and gigi people you would think are off doing yoga, they're now boxing. >> why is this taking off like this? >> one, because it works. it's incredibly efficient especially co