Please choose the correct ending to complete the given sentence: Health: [header] How to flex your back [title] Do abdominal exercises. [step] Abdominal exercises will flex you back each time you roll your body forward or to the side. Include a few abdominal exercises in your regular exercise routine.

Ending1: Try the following combinations : [substeps] Stretch at least three times a day. This will increase your flexibility and prevent injuries. Ending2: Specific physical exercises that target specific muscle groups should not be attempted on surfaces with specific target areas. [substeps] Swimming and swinging your arms forward and to the side should be two examples of abdominal exercise. Ending3: [substeps] To do these exercises, sit in a comfortable position. Slide your lower back back forward as far as it will go, hold for 30 seconds, then slowly lower your back. Ending4: There are lots of different abdominal exercises you can try including : [substeps] Sit ups crunches oblique crunches do bicycle crunches | bicycle crunches] ] [title] Try supermans. [step] Lay down on your stomach with your arms straight out in front of you and your legs straight out behind you.

Answer format: ending1/ending2/ending3/ending4