Please choose the correct ending to complete the given sentence: Health: [header] How to make treadmill exercise more interesting [title] Do a treadmill hiit workout. [step] Hiit workouts or high intensity interval training are a popular new form of exercise. These types of workouts have a variety of benefits and can be done with any type of cardio equipment including a treadmill.

Ending1: Most people recommend that on a low-impact training program, large treadmill or run will provide intense burns for many minutes. If with high intensity walking on your treadmill you do not want to hold it for too long you can exercise under your upper body for 300 to 500 minutes. Ending2: [substeps] Hiit workouts are usually a little shorter in length-maybe 20-30 minutes-and alternate between very high intensity exercise and more moderate intensity exercise. On a treadmill, you can alternate between sprinting and jogging or between jogging and running on an incline. Ending3: [substeps] You don't have to go to the gym, and you can also improve with a speed increase class. These can be controlled by personal training trainers, as well as tools like dumbbells, dumbbells, and resistance bands. Ending4: [substeps] By either using a machine like a treadmill or rowing machine with low resistance, you can use an exercise that requires little effort to do. The treadmills and push up machines are incredibly low impact.

Answer format: ending1/ending2/ending3/ending4