I have a habit of reading a little bit of anatomy as related to Yoga and something about birthing in the evening before going to sleep.
Last night, I read about something which is called the "Clasp Knife Reflex", which is the reflex involved in causing muscles to relax by applying pressure to them, either through muscular tension or manual stimulation. I also read about water - specifically a bath - as an effective form of pain relief during labor. Interestingly, there seems to be a similar mechanism at play in both.
To understand the Clasp Knife Reflex, think of trying to close a pocket knife (hence the name of this reflex!) by applying pressure to it. The knife resists closure up until a certain point, and then suddenly snaps back into place. When a person loses an arm wrestling match this reflex is what causes the arm to drop down and relax suddenly after so much pressure being applied.
This reflex explains why deep tissue massage can have such a relaxing effect on the body even days later.
Activating the Clasp Knife Reflex happens very often in Yoga and can be very effective in increasing one's flexibility and releasing muscular tension. One example is demonstrated in a variation on a Forward Bend, which you can try yourself. This is a great pose to do first thing in the morning as the muscles can get very stiff as we sleep during the night and this is a wonderful way to open up the whole body and alert the mind to increase your energy during the day.
1 - Come into a forward bend with your knees straight
2 - Let your arms hang loosely and notice if your hands reach the floor and to what degree (i.e. can you get your whole palm on the floor or just the fingertips?). If your hands don't reach the floor, just notice the distance between your hands and the floor. (Don't worry - once upon a time my hands were up up and away from the floor as well!)
3 - Bend your knees just enough so that you can rest your torso on your thighs.
4 - Wrap your arms around the back of your thighs clasping your elbows or forearms to lock them in place
5 - Take a long inhale and look up, increasing the bend in the knees slightly
6 - Exhale and look down, and try to straighten your knees as much as you can, while keeping your arms in place.
7 - Hold this position for a good 30 seconds, moving against the tension and perhaps the desire to either bend the knees or release the arms. - This is what we call an "Isometric Pull".
8 - Release your arms and see how much further down you can fold into that original Forward Bend.
Pretty cool, no?
Although I have not seen the term "Clasp Knife Reflex" written in reference to labor, we can see a similar idea of how applying pressure can actually relieve pain and internal tension, in the use of water, specifically bathing, as a form of pain relief during contractions.
Dr. Michel Odent, MD (as quoted in the book The Birth Partner by Penny Simkin) explains some of the physiology behind why so many women find taking a bath at certain points during labor to be so effective at relieving pain.
"....The warmth and buoyancy of the water brings about relaxation and relief of pain. This lowers the production of stress hormones (such as a adrenalin) which are known to work against oxytocin and to slow contractions.... The weight of the water (hydrostatic pressure) against the woman's tissues presses fluid from her arms, legs and skin into her circulation, which markedly increases her blood volume, especially in her chest and heart..." (118-119)
It is interesting that he mentions adrenalin, a hormone which is produced during high impact aerobic exercise as well. There are certainly many benefits to adrenalin, however it must be kept in mind that adrenalin can increase stress and tension in the body, and can actually be counterproductive if there is too much. As mentioned above, in childbirth, adrenalin can actually slow contractions! This is perhaps one reason why so many athletes are increasingly dong Yoga these days, which can be such a great antidote to the physical stress placed on the body in so many other sports. Additionally, it has been reported, that a regular Yoga practice can actually increase athletic performance.
Keep in mind, Dr. Odent is very specific in terms of his promotion of the use of bathing during labor and recommends the following guidelines.
- The mother should not get into the bath too early as this will not bring benefit and may even be counterproductive. His recommendation is that the cervix should be at least 5 cm dilated, at which point the bath may help her progress in opening up further as well. One exception to this rule is if a woman is experiencing a very long, uncomfortable pre- or early labor, in which case a long bath can be helpful in stopping her contractions so the mother can rest up.
- The mother should not stay in the bath for a prolonged period of time - he says 1.5 hours is the max. More than this, and the effect will wear off, and/or the contractions may slow or stop entirely.
- The temperature is important. Room temperature (98.6 deg F/37 deg Celsius) is ideal. If the water is too warm, this may G-d forbid cause the baby to develop a fever, which can be a serious issue.
Just to link this last point to the above Clasp Knife Reflex as applied to Yoga.... Putting pressure on a muscle... is it good or bad? It all depends on the amount. Every body is different, and while isometric resistance can certainly be an effective way to release muscular tension and increase flexibility, make sure not to push yourself too far! A skilled masseuse will know just how much pressure is enough, but not too much, to get at those really deep knots, without hurting their client.