Mudras : Gestures of the Hands and Fingers For Amazing Health Benefits

What are Mudras? How do we define them? As per Eastern philosophies and culture and Yogic practices, 'Mudras' are systematic hand gestures. Literally, Mudra in Sanskrit means a posture/seal More deeply, "closed electrical circuits" of the subtle channels in physical and etheric bodies are also known as 'Mudras'.
Some Western writers have defined 'Mudra' as mystic hand gestures used to focus subtle energy, transmit teachings through symbols and confer psychic protection.
Chogyam Trungpa says Mudra is "a symbol in the wider sense of gesture or action………Also it is a symbol expressed with the hands to state for oneself and others the quality of different moments of meditation……."
Leaving aside the complex definitions offered by various people and sects, we will summarise to say that:
Mudras are a non-verbal mode of communication and self expression consisting of hand gestures and finger postures. They retain the efficacy of the spoken word. It is an external expression of inner resolve, suggesting that such non verbal communications are more powerful than the spoken word.
In Yoga mudras denote the finger and hand gestures and movements used in the performance of dances, rituals and rites and while engaging in spiritual exercises such as meditation. Mudras symbolically express inner feelings and inner psychological states. They also generate various qualities such as fearlessness, power, charity and peace in the practitioner and to on-lookers.
The Gherand Sanhita and the Vajrayana Tantra advise that the Mudras are capable of bestowing great powers and  psychic abilities called "Siddhies" on their practitioners, hence, their knowledge should not be conveyed to those steeped in sin,to those that are not true to their word, to the skeptics and non believers, to heretics and insincere persons and those who do not observe the precepts.
Mudras have therefore always been considered an esoteric science and even as of date there are thousands of Mudras that are not available to the uninitiated (like in the Chen Yen Buddhism or True Buddha Schools). However, besides the mudras providing spiritual gains, there are mudras which are likewise of tremendous value in therapy. Constant researches by the dedicated have brought a large number of these to the fore although we still seem to be scratching the surface only of this sea of knowledge.

Most commonly known mudras and how they affect the body

Gyan Mudra : In this position the fingers are held with the tip of the index finger touching the tip of the thumb and the remaining three fingers nearly straight--kind of like an "OK" sign, except the palms of each hand are pointed up or front.
This mudra is good for: stresses and strains, insomnia, emotional instability, indecisiveness, excessive anger, idleness, laziness, indolence, and is a great help in increasing memory and I.Q. It can help cure sleeplessness and get one off sleeping pills where these are being taken.
There are a number of variations of this mudra for higher and higher degrees of attainment e.g. Purna Gyan Mudra, Vairagya Mudra, Abhay Mudra, Varad Mudra, Dhyan Mudra, Mahagyan Mudra. As one keeps attaining higher and higher levels of the mind, the mudra's change. Read More....

Vayu MudraThis finger position is unbeatable in quickly and effectively removing the accumulated wind in the stomach. Depending on one's physiology, it may take anywhere from 1 minute to 15 minutes or so to effectively expel all accumulated wind in the stomach without the use of anti-flatulants. Mudra should be stopped when the trouble abates.
It helps in alleviating all wind based aches and pains. Considering that almost 80 % of the body's aches and pains are due to wind, the practice of this Mudra is a must, before taking recourse to any other treatment. It is very effective in Parkinson's disease (an ailment of the nerves where the patients body, head and limbs shake uncontrollably). Read More....

Shunya Mudra : This helps those with impaired hearing. If there is no physical defect, the mudra, if practiced regularly, can restore the hearing power. Remarkably, it helps in getting rid of earaches within minutes. It takes no mare than 2 to 3 minutes to get rid of most earaches.
It helps in relieving the nausea and vomiting sensations felt while driving on winding hilly curves or while taking off or landing in aircrafts. It helps in many problems of vertigo. The mudra should not be continued after the problem has been removed. Read More....

Apan Vayu Mudra: This finger position works like an injection in cases of a heart attack. Regular practice is an insurance in preventing heart attacks, tacho-cardia, palpitations, depressions, sinking feeling of the heart. Also known as the Mritsanjivani Mudra for arresting heart attack.  Read More...

Pran Mudra : This finger position is an all time useful Mudra and can be done for any length of time, any time, any place and will only help in adding to the benefits. This is the mudra which, along with the Apan Mudra, precedes any efforts at higher meditation by the Yogis and saints. The mudra helps to increase the Pran Shakti or the "Life force". It increases one's self confidence. It helps the body in increasing it's vitality and sustenance when deprived of food and water. 
It helps in improving weak eyesight and quiescence (motionlessness) of the eyes.
It supports any other treatment where the patient is short on confidence.
Here are some more mudras which are useful in therapy. There can be no end to the gains that may be had from Mudras. While for most Mudras there are no restrictions of posture and time, others should not be performed without full knowledge. In some cases, practice for longer periods or while in a different posture or at the wrong time could even prove harmful. Read More....

Aakash Mudra:  Helps to remove weakness of bones, hearing deficiency.
This Mudra should not be done while walking

Apan Mudra: Helps in purification of the body, urinary problems, easy secretion of excreta, regulating menstruation and painless discharge, easy child delivery, Piles, Diabetes and kidney disorders.
: This Mudra should not be done by pregnant ladies before completing 8 months. After that a 10 minutes practice 3 to 4 times a day will ensure normal delivery.  Read More...

Ling Mudra:: Generates heat in the body. It destroys phlegm and helps in problems of colds, catarrh and coughs. It is excellent when the body is cold due to shortage of cover in inimical weather. This mudra must be performed under supervision or with full knowledge. Read More....

Varun Mudra: A miracle mudra for Skin problems, wrinkling, loss of glow, dehydration, excessive body heat, blood disorders. Read More...

Prithvi Mudra : Increases solidity in the body. Removes weakness, lack of body solidity. Helps gain for underweights. chronic fatigue and weakness. Read More...

Surya Mudra: It helps to reduce the accumulated fat in the body and unwanted cholesterol. in accumulated fat in body, reduction in cholesterol. Read More...

Shankh Mudra: Tone therapy, speech defects, Indigestion, loss of appetite.

Meao Mudra:  Excellent in bringing the Blood Pressure to normal from either high or low.

Yoni Mudra Helps to overcome loss of virility, loss of Satwik Gunas ( pure qualities)

Kamajayi Mudra Helps to gain control over unsuppressed passion and sexual urges etc.

Vyana Mudra: To be alternated with Meao Mudra for High B. P. only.

Surabhi Mudra or the Dhenu Mudra: Is a very effective and powerful Mudra. By itself this Mudra helps a sadhak (an aspirant practitioner) to break any barriers which he may face when on the thresh hold of samadhi (the ultimate meditation).
In this Mudra the ethereal elements combine such as to magnify and multiply their powers and produce powerful results on the body. Vayu (Wind; symbolised by the first finger) meets Aakash (Ether; symbolised by the middle finger), to stabilise the chakra (the circle) of the universe. Again Prithvi (Earth; symbolised by the ring finger) meets Jal (Water; symbolised by the small finger), to produce the generative power of the universe.
With constant practice, this mudra helps to stabilise and bring in resonance the Nabhi Chakra or the circle of the navel, so essential for the ultimate elevation of the human mind and body. The mudra has 4 variations, each of which gives different results.

Aatmanjali Mudra: Helps in centering the consciousness of the mind.

Vayu-Surabhi Mudra A variation of the basic Surabh Mudra, it helps to eliminate all ailments resulting from the increase of wind in the system.

Shunya Surabhi Mudra By increasing the ethereal vacuity it helps the sadhak to increase the hearing power manifold.

Prithvi Surabhi Mudra Helps to cure all ailments of the stomach generated due to defects in the digestive system. Specially effective for people with chronic digestive ailments.

Jal Surabhi Mudra This mudra helps to cure and eliminate diseases related to bile. It helps in curing diseases related to urine and assists easy passage.

Girivar Mudra: urinary problems, purification of body
In short, Mudras can be our best friends to help us maintain good health and when needed, to help overcome many ailments and diseases effectively and without harm to the body.
First give the body a chance to heal itself before giving it invasive medicines and drugs, which must and will have some side effects.

Also know the Seven Mudras Which Swami Ramdev recommends with Pranayama