Mixing fitness with fun was the order of the day for 40 ST Run participants yesterday. At Bounce Singapore in Cathay Cineleisure, they torched calories, working not just their legs but also their core muscles, as they bounced on the trampolines. The Bounce Fit sessions were the second build-up activity for this year's The Straits Times Run on Sept 23. Look out for more activities on www.straitstimesrun.com.