Please choose the correct ending to complete the given sentence: Health: [header] How to raise your heartbeat [title] Change how you sit. [step] Instead of just sitting in a normal chair, try sitting on an exercise ball instead. Sitting on an unstable surface engages and strengthens your core muscles while sitting in a normal chair does not.

Ending1: Different people put different positions on the ball. Try to try different positions to increase your comfort. Ending2: You can even forgo sitting, and stand as much as possible during the day. Even these small changes can affect your heart. Ending3: [substeps] Exercise balls may help you urinate, push yourself, or widen your abdominal opening. Replace an exercise ball with a cloth or a ball kept in a safe place. Ending4: On a standing stability ball, push yourself up, keeping your leg and arm resting on the ball. [substeps] Try some variation of the seated adjustments.

Answer format: ending1/ending2/ending3/ending4