Please choose the correct ending to complete the given sentence: Sports and Fitness: [header] How to exercise using your stairs [title] Walk or jog stairs. [step] If you've ever had to climb up several flights of stairs, you know that walking stairs is a serious workout. It helps get your heart pumping and breathing at a faster pace.

Ending1: [substeps] If you've never climbed stairs before, start by walking 3 times a day. If you do it regularly, you should be able to do this by the end of the week. Ending2: [substeps] Walking increases blood volume to the areas where your heart beats. If you can't access the stairs regularly, work on switching to stair climbing exercises while walking down to give your heart the time to work up. Ending3: This is why it's great for cardio. [substeps] If you can, try to find a long flight of stairs. Ending4: Walk, jog on the stairs or jog on the pads using your toes or heels. [substeps] Whenever possible, start your day with your stairs in mind and also walk around the house carefully.

Answer format: ending1/ending2/ending3/ending4