This is not recommended if you have back problem.
1. Find a straight back chair and sit down with your back fully pressed to the back of the chair.
2. Slowly bend over in the tuck position with your arms crossed over your body - the same way you would bend over when an airline stewardess instructs you to take when they say get in the crash position. Do this until you feel slightly uncomfortable.
4. Stay in the same position but relax then repeat this procedure again for at least 2 to 3 times again. Then slowly sit back up.