Underground Fitness II 3900 Newpark Mall, Newark, CA94560 Underground Fitness II is a dance and fitness studio that offers classes for Zumba, U-Jam and Turbo Kick Boxing. Classes…More are offered 7 days a week with class times ranging from 6am to 8:30pm. Classes can be reserved ahead of time or paid on a drop-in basis. U-Jam fitness is an athletic hip-hop fitness workout that combines easy-to-learn dance steps with high-energy music to get the body pumping. Also, yoga will soon be added to the classes offered here.