Hello, welcome to healthcaremagic. The issue you are facing are due to lack of regular exercise and are faced by majority of people. Inadequate exercise limits the stretching ability of muscles especially of the back and legs. When you try to touch your toes while standing your muscles get streched beyond their capacity causing pain to you. To overcome this you need to exercise on a regular basis. Wish you good health.

Hi,
Welcome to HCM.
You have not mentioned your age. Forward bending is restricted, if there is any problem in the vertebral column, or if you are not used to doing such thing. If forward bending causes pain, you should consult an orthopedic surgeon to exclude vertebral pathology such as slipped disk.
It is better to avoid forward bending exercises, as they may create problem later in life. If you cannot touch your toes, do not attempt to do so.

Hi,
That some who told you so, is wrong. It is true that with age, flexibility of your body decreases, but it is not true that by increasing flexibility of your body, your body gets younger. Body cannot get younger than your chronological age, though you can keep your body fit by regular exercise. Don't over do it, otherwise it will have directly the opposite effect, i,e. your body will suffer irreparable damage.
As I told you earlier, avoid forward bending exercises.