HIIT stands for high-intensity interval training, which refers to the short bursts of intense exercise alternated with low-intensity recovery periods that make up the protocol. HIIT is quick and anything but boring, as its exacting work-to-rest ratios make it arguably the most time-efficient way to exercise and burn calories. You can use the HIIT protocol to build your entire workout, or apply it to just a few sets to create super-charged finishers. Find out more here