If you want to try high-intensity interval training, it’s as easy as remembering these numbers: 30-20-10. That’s an equation that adds up to exercise success according to research from Denmark. So choose your favorite form of cardio and go easy for 30 seconds… increase your exertion for the next 20 seconds… Then go all out for 10 seconds – and repeat that pattern 10 times. That’s the 30-20-10 method. When people in studies tried it, they improved their overall fitness and lowered their blood pressure.