Front Kundalini
Front kundalini is relatively unknown. It is not discussed generally when we speak about kundalini yoga. Back kundalini or spinal rise of kundalini is the convention. That is well known and to some degree it is understood theoretically even by person who never experienced the rise of kundalini through the spine.
Front kundalini is not regulated by chakras as the spinal kundalini is. After years of practice of spinal kundalini where one experiences the rise of kundalini in a rapid or slow motion through the central spine (sushumna) into the brain, one may begin to get experiences of front kundalini from time to time.
At first this happens because the kundalini finds an upward passage through the central front part of the body right under the skin or through the middle of the body, smack center. In that movement, the same spinal kundalini operates but instead of travelling up through the spine, it travels to the front of the body and enters a subtle passage which is either smack center in the trunk or to the central front under the skin.
This is not that surprising because in sex pleasure experience, the same spinal kundalini becomes engaged linking itself to the sex/reproduction chakra complex where it runs through channels in the front of the body in the region of the genitals These channels were there before one experienced sexual climax pleasure but they were in a dormant unobservable state.
There is another frontal kundalini rise however. This is the sparking of the kundalini of each cell either in one part of the body or in the entire form or in particular organs. Each cell concerned then flashes its mini-kundalini energy. This is felt collectively as a neutral, pleasant or super-pleasant bliss force. It has a sense of direction and either converges on itself imploding or diverges from itself exploding or even trickles up through the body with a sense of direction of going upward.
Mastery of spinal kundalini may cause the yogi to attain siddhaloka special astral realm. In that skill sex energy is used where it is mixed with infused breath energy and causes the kundalini to go upward through the spine into the brain causing spiritual insight by arousal of brahmrandra crown chakra.
Yogis who reach siddhaloka may go higher but there is the likelihood that the yogi may again take another material body where he may or may not achieve higher states which would solidify for him the need to not have a physical form.
A yogi who attains siddhaloka, either while he uses a physical body or otherwise, is likely to go higher if he can become more proficient in kundalini yoga where his kundalini energy, which was attracted to the sex-reproduction complex, uses that energy to go upwards through the front of the body.
Other yogis who advance further with breath infusion, and who directs the cells of the body to release their micro-kundalini flash charges upwards in the body with no attraction to the sex/reproduction complex would go to the brahmaloka place which is higher than the siddhaloka location.
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On Brahmaloka, the subtle bodies have no kamarupa or sexlust completion actuation content but they do have the impetus for sexlust to be completed elsewhere. This means that there may arise a desire for sexlust even in brahmaloka but the energy would be stalled. It could not be completed because that environment does not have the environment to support it.
To understand how this is possible, we may consider a prepubescent child who has a gender based attraction to some other child. Two such children may attempt to do a sexual act but it would not happen because the bodies would be unresponsive. It is not possible to complete a sexual act in the brahmaloka dimension but the desire for such an act could be completely elsewhere just as in the case of the those two children who felt gender attraction and could have sexual acts only when their bodies matured after puberty.
There is bliss pleasure in the brahmaloka place but this energy has no lust potential. A man or woman can enjoy someone of the opposite sex there but it would be without lust yield. However the same couple may be engaged in lust acts as soon as they transited out of that realm into a place which supported sexual lust connections.