HIIT means High Intensity Interval Training. HIIT exercise in COPD is an alternative approach to training than the lower intensity, longer duration exertion used in many pulmonary rehabilitation programs. It is a popular type of a cardio work-out - could be walking on a treadmill, cycling on a stationary bike, using a stair climbing machine, rowing, jumping rope, etc. HIIT is an intense level of exertion for a short time period. One example involves a 2:1 ratio of walking fast on the treadmill for 30–40 seconds followed by 15–20 seconds of easy or slow walking to recover.