Please choose the correct ending to complete the given sentence: Sports and Fitness: [header] How to do russian twists [title] Place a mat or towel on the floor. [step] Place the mat near a couch or another piece of furniture that has a small, but big enough, space to stick your feet under. The resistance from the couch will stabilize your body while you do the twists.

Ending1: If you can, lay down on a mat with a pillow under your head. [substeps] Avoid putting a rug under your thighs, as this will cause swelling and discomfort. Ending2: Lie down on the mat with your knees bent and place your feet under the couch. [substeps] Alternatively, you can have a friend hold your feet down for you instead of the couch. Ending3: [title] Grab a piece of 4-inch (10-cm) thin cord. [step] Stretch 1 end of the cord to your body between your elbows. Ending4: [substeps] If your mat or towel is of a heavier material, such as plywood, make sure to cover it with a few layers of wrapping newspaper. Place a mat in front of a television set for a more dynamic twist, or lay flat on a couch.

Answer format: ending1/ending2/ending3/ending4