Private equity firm Silver Lake is set to invest in Equinox Fitness, an operator of fitness clubs and spas. Financial terms were not disclosed. The funds will be used to build Equinox’s digital platform and add as many as 50 locations annually. “As we accelerate our expansion while delivering a first-of-its-kind online/offline experience for our growing global community, Silver Lake is providing valuable expertise as well as capital to fuel this next stage of growth,” Harvey Spevak, Equinox CEO.