This tweak of a classic high-intensity interval session is described in the work of Vaccari and colleagues (1-2). Vaccari found that high intensity intervals with decreasing effort duration results in greater time at >90% of VO2 max than traditional long intervals and short intervals. Why could this added time above 90% of VO2 max be important? For years, we've assumed that performing high intensity intervals at an intensity higher than 90% of VO2 max is beneficial to adaptation. But we...