At your age it is very likely that you have stopped growing.
There is very little chance that exercise can help you increase your height
but there are a few things which will elongate your body and possibly increase
your height.
Yoga and Stretching
Yoga and stretching your entire body is great for bettering your posture.
If you have muscle imbalances and poor posture your body could be shorter than
it would be with perfect posture.
Foot Orthotics
Foot orthotics or special foot inserts created by an podiatrist can help your
posture by strengthening the arch in your feet. If you have flat feet
orthotics can help put your body in proper alignment and increase your height
while you wear them and you're wearing shoes most of your day.
Staying Hydrated
Your intervertebral discs are filled with water. In between each
vertebra in your back you have one. If you are chronically dehydrated
there is a slight chance that your discs cause your body to be slightly shorter.
Stay properly hydrated by drinking enough water and you could possibly
increase your height slightly.
At 20 years old, your body has 99% most likely naturally stopped growing.
Be extremely weary and skeptical of any claims that tell you you can use
exercise to grow taller.
There is actually an entire website devoted to growing taller and includes
exercise to grow taller.
