If you have been on the path long enough and are not steeped in hedonism and have opened your Chakras and maintain balance you can use methods within Tantra to directly access the Sushumna.
Cautions are for those not yet ready and or have Karmic issues to be resolved.
Mulabanda, Asvani and Tada Mudra are means to open and close the valve gates of ida and pingala. These and various other actions cause the anal sphincter bands that are wrapped 3 times approximately to form the inner anal sphincter bands of the 1st and 2nd internal sphincters. [Kundalini is said to wrap 3.something times in a coil, which is an analog to the 3 bands of the sphincters] Just as ida and pingala correspond to parasympathetic and sympathetic nervous sytems, so do they correspond to the 1st and 2nd anal sphincters. Note the 1st anal sphincter is under the conscious control of any human being, its the 2nd anal sphincter that is under unconscious control[of the 1st and 2nd Chakras].
The flow of Prana, Chi or Kundalini is fully interdependent upon the muscle tonality of the 1st and 2nd anal sphincters. If you are uptight and hold stress in your anus you will squeeze your anus super tight and hold it that way throughout your day and life. This is representative of a CHAKRA Blockages in the lower Chakras. You may have issues and need to work through them to relax the valve gates and allow your Chi\\prana\\kundalini\\holy spirit to flow.
Mulabanda, Asvani and Tada Mudras are all means to impact the tonality and the overall ability to willfully expand or contract your anal sphincter muscles among other muscles of the pelvic floor including the perineum.
The relaxation of the 1st and 2nd anal sphincter is akin to your ability to open and close the flow of ida and pingala at will and when you can do so in the correct proportions you can infuse the Sushumna and allow Shakti to flow upward to Shiva and Shiva to flow back again to Shakti in a complete CIRCUIT.
If you have actually taken the time to complete the Circiut you are likely to spiritually adept enough to directly access the Sushumna, lest you risk getting stuck or lopsided in your Chakras our pull negative Karma you way.
The Degree of Relaxation of the Anal Sphincter Muscles directly impacts the flow rate of the Nervous system Circuits, in effect increasing the flow rate is analogous to greater conductivity, with the goal of superconductivity. The less resistance in the nervous system the more electricity can flow via the nerves.
The more of an open Channel you are and if you have sufficiently removed Chakra Blockages the more prana will flow up the Sushumna, which will be proportionate to the intensity of the feelings you experience. Be these mystical, sexual, mental or spiritual, or some combo depending on your path.
So the question becomes how uptight are you how much stress to you store in your sphincters, as this will relate to the quality and duration of your experience that are dependent on Chi flow. Such as mystical, sexual, or mental\\spiritual experiences and their respective intensities.
The degree of relaxation and dilation of the anal sphincters is directly related to the flow of prana up the Sushumna. If your anus is to tight your not relaxed and have a Chakra blockage and need to work though it.
Mulabanda, asvani and tada mudras [akin to western Kegal exercises], give fine motor control over the 1st and 2nd anal sphincters. Which also stimulate the Kunda (kundalini gland) into contractions, which push spinal fluid orgasmically up the spine into the back of the skull resluting in a gush or flood of biochemicals in correspondence to the rise of Kundalini and peak experiences such as Samadhi.
Samadhi by degree related to how open the flow rate of ida and pingala is into the sushumna. Bliss and pleasure are also directly related to this.
Here in lies a danger, because if you 're not spiritually adept and experience profound orgasm via the practice of Adhorata a specif anal kundalini arousal method, you can forget the ULTIMATE Sources of all pleasure and bliss and mistake your sexual organs as the ultimate source, in effect taking the smaller to be equated to the whole, which can lopsided you and make you seek sexual pleasure over the pursuit of ultimate truth and the ultimate spiritual reality of love, which is a primary goal of Tantra itself.
Direct access to the Sushumna can be achieved via ADHORATA to a much greater extent then Mulabanda or asvani or tada mudras. This is because ADHORATA directly dialates the anal sphincters and can cause PROFOUND relaxation and pleasure by direct access to the sushumna and directly pushing Shakti to Shiva, a spinal orgasm of Directly upward flow of Prana, Chi or Kundalini.
If one is already enlightened this is still JUST BLISS and when its in its proper context is still as SACRED as any other form of Samadhi or blissfull states of experience resulting in the rise of Kundalini.
All form of orgasm are derivations of this process and are by degree the same flow, but it can become more profound via all sorts of practices. ADHORATA is just the most direct access and can be a profoundly pleasurable orgasmic experience that can be unmatched, especially when yoni stimulation is occurring at the same time. If you keep this in its proper context the experience is SACRED and PROFOUND. There is not a more direct root to flow blown bliss, one just be careful not to get trapped by the physical pleasure alone that results from the profound opening of the nadis...
If you perform the SACRED act of ADHORATA and climax, and then instantly experience contractions and discomfort you are likely holding way way to much stress in your anal sphincters and are probably uptight at some level and have 1st and 2nd Chakra blockages of some kind.
It takes time to learn to relax the internal 2nd anal sphincter, this is the hard part to learn to control this at will, mulabanda, asvani nd tada mudra can help you with this, mostly asvani mudra. All pleasure is dependent on this 2nd internal anal sphincter, you will never derive any pleasure of open the gates to the sushumna until this 2nd sphincter learns to properly let go of tension. A toned sphincter can open and close at will, a blocked one stays puckered up so tight, anything hurts and Hemorrhoids and anal fissure can result from holding to much stress in the 2nd anal sphincter.
The sphincters are the valve gates of ida and pingala and thereby dictate the flow of prana into the sushumna, of which all bliss, orgasm or pleasure of any kind are derived. States of meditation are also related to this level of relaxation although one may be unaware of these connections. All the nerves and the sexual organs or interconnect with those of the anus and rectum, when aroused the anus and sexual organs function as a single unit via the same systems of nerves and contact together rhythmically during orgasm.
ADHORATA can result in states of Samadhi by degee of activation of the Kunda [kundalini] gland. Adhorata directly stimulates this gland physcially to a far greater extend the Mulabanda or asvani mudra ever could. Sacrum pressure can excite the kunda gland as well which is why Tada Mudra can activate this gland as well. ADHORATA achieves the same things as tada Mudra by repeatedly hitting the sacrum and applying external pressure upon the sacrum in addition to direct physical stimulation of the kundalini gland.
