These were an ancient practice in the realm of hatha yoga designed to strengthen and empower.
traditionally all part of the Kurushetrya warrior training in ancient India, they were the source of many of the martial arts that are now an intricate part of most Eastern cultures.  The roots of these hatha martial exercises go back to early times, through Egypt to the Atlantean civilization that spread out to the four corners of the world after the continent submerged. See History...

I was introduced to hatha yoga dandhals in 1970 through a book called "Yoga and Health" by Yesudian and Haich. It involved a series of slow-moving muscular exercises which emphasized the contraction of muscles for body building and strengthening purposes.  While most hatha exercises are designed to stretch and relax the muscles, these dandhals went the other way - actually thickening  the muscles and possibly stiffening them. These exercises needed to be complemented and balanced with the stretches. On the other hand the stretches also need to be balanced with strengthening and building. Over the decades I have also seen that these grounding exercises are also very important when working with the chakra energies.

I admit to not working much with them in the first two years of my practice, partly because they were not taught at the ashram where I studied.  Classical hatha was taught with all the emphasis on stretching muscles, and that is where I formulated my practice, increasing flexibility and liberating pent-up energy, then awakening of latent energies and development of the Chakra forces. It took me a few years to discover the importance of bodybuilding in the yogic system.

What Yesudian and Haich were elaborating in their book, which also had an extensive section on hatha yoga stretches, was slow motion muscle contraction with concentrated awareness on feeling the muscles as they do the work.  At the same time, breath was used to deeply inhale the oxygen and prana, while then directing these to the muscles on the expelled breath. Visualizing the muscles being pumped was part of the practice as well. Unlike the blind repetitions advocated in modern fitness programs while thinking about something else and listening to music, the dandhal method unified mind, energy, emotion and body into one technique. 

At the time I learned of this system there was not a lot of documented research on yoga.  Now there is. Stephan Cherniske in his book “The Metabolic Plan” and “The DHEA Breakthrough” is quite adamant on the fact that strenuous exercise involving hard muscular workout is the most effective way to stimulate the body's restoration and rejuvenation functions. This function by and large works through a hormone known as DHEA (dehydroepiandrosterone) secreted in quantities by the adrenal glands when they are not in stress mode - secreting epinephrine. This process continues until age 30, after which the levels decreased rapidly and we begin to age. The trigger for us conscious humans lies in the effort we put into strenuous exercise. Not just doing them but taking them a little further than we feel like -- doing it one more time in spite of the body and mind resistant. The reaction to these extra muscular contractions is stimulation of the adrenals and the subsequent release of DHEA which contributes to over 150 different metabolic functions, functions that keep us strong and youthful.

Body chemistry is all quite interlinked, always balancing itself and adjusting whatever needs be.  Many of the needs meanwhile are determined by our expectations and beliefs around what we think we need. This is a very flexible arena which has become co-dependent on what everybody believes compared to our own belief system. Modern research by Bruce Lipton has verified that every cell in our bodies is ultimately directed in its reactions by our state of emotion and expectation. Hatha yoga in general as well as the dandhals, bring all of this together when properly practiced. Consciousness is present, mind is focused, and emotions are involved in feeling the effects of what we are doing.

I first applied the dandhal technique in 1975 three years after the ashram experience when my body weight was at minimum. I had done lots of stretching and fasting to bring it to that point while working extensively with visual concentration and painting mandalas. I was very flexible, yet I had no physical strength. I had returned from Guatemala rather weak and underweight and came to stay at my brother's place. Gene, my brother had been taking karate and kung fu lessons to develop his strength and stamina. I felt a little bit like a scarecrow beside him so at that point decided to activate my dandhal practice. I wanted to regain strength, weight and body bulk and finally applied the dandhal technique.

I used some rocks that I found out in the forest as weights to trigger some of the cardiovascular feelings in my muscles. For the other slow-motion dandhal exercises I simply performed different types of curls and pushes imagining the resistance as in conventional dandhal practice. I added breathing sessions before and after the workouts and every movement of the arms or legs was accompanied with a movement of the breath, that breath always being deep. I also took eating breaks in which I used a lot of milkshakes made with milk, eggs, bananas, plus a few other goodies. Throughout the day I went from exercising to breathing and eating to relaxing and breathing to exercising, then breathing and eating again. This I did all day long. The response to my body was rather immediate and within 48 hours I had gained 6 lbs. This did impress my brother and his karate instructor who was living in a suite downstairs in his house. The weight gaining moderated after that point but I continued gaining approximately 1 pound per day for the rest of the month. Over that month I went from 105 pounds to 135 pounds, my body filled out immensely with muscle and I felt incredibly strong and empowered. Psychologically it also created a state of confidence, ability and empowerment.