On Friday at 8:20 a.m. on the dot, Kirsty Godso and Lauren Williams started to teach their new class, Pyro Girls, at Project by Equinox, a boutique fitness studio at 267 Mulberry Street in SoHo.

“Everyone in this room is now a pyro girl,” exclaimed Ms. Godso through a microphone. “That means you don’t just accept anything, you are going after more, you are fiery. We are going to get lit up.”

The class, a mix of strength work and high-interval training, was carefully created by the trainers, who are close friends. Participants, dressed in bright-colored leggings, cut-up T-shirts and the latest name-brand footwear, grunted through intervals of burpees with names like hot sauce, Bloody Mary, and jalapeño.

By the end of the 50-minute workout participants were drenched in sweat and keeled over. But rather than run straight to the locker rooms, they stayed behind to chat with the instructors. Some requested selfies. Others needed clarifications on moves. A large group headed to the adjacent lounge where they helped themselves to free cold brew, laced with nitrogen for an extra kick, and analyzed the workout.