Hi Natalie
Yes, there was a lot covered in the course and it is not surprising that you don't remember it all: no one does. But, we did cover some of this in the section on the Mind Body when we talked about breathing. Hyperventilation is when we blow off too much carbon dioxide which can cause the blood PH level to become too alkaline. The solution is not so much breathing deeply, as that too can cause hyperventilation, but rather to breathe more slowly, which is why nose breathing is preferred, as it slows down the breath. Slowing down, or indeed holding the breath, can give time for the CO2 to build up again in the blood. You may recall the 10-second Ocean Breath slide? Breathe in to the count of 4, hold for 1, exhale for 4, hold for 1: this will increase CO2 levels, lower heart rate, blood pressure and improve heart rate variability. Here is a short section from my latest book, Your Spine, Your Yoga which talks about the breath:
- IT'S IMPORTANT: Slowing the breath is better than deepening the breath
We are all different, and our differences can affect the way we use our breath while in meditation or while doing our physical yoga practice. Lengthening the breath so that we breathe six times a minute improves our heart rate variability, turns off the “flight or fight, response (the sympathetic nervous system) and stimulates the “rest and digest, response (the parasympathetic nervous system). But this slower breath does not necessarily mean that the breath must be that much deeper! Due to a variety of complex chemical cascades, slow, shallow breathing may be much healthier for most of us than deep breathing (see the Web appendix “How yoga affects our blood chemistry, for the details). One good way to ensure the breath is slow but not necessarily deep is to breathe through the nose. This is done in most forms of pranayama practice, but one particular form has been specifically studied. It is called alternate nostril breathing, and it involves inhaling through the left nostril and exhaling through the right, then switching and breathing in through the right and out through left. Also called nadi shodhana, nadisudhi pranayama or anuloma viloma, this practice has been shown to reduce heart rate, breathing rate and diastolic blood pressure. Next time you are feeling anxious or a bit on edge, try it out-breathe slowly through the nose, and see whether it works for you.
There are several reasons why someone's heart rate may increase during Yin Yoga, but not all of them are breath-related. If a student is too deep in a pose and the sensations are too challenging, this could trigger an emotional response of anxiety or fear, which may trigger the sympathetic nervous system (SNS), the fight or flight system, which will increase heart rate. Or, if a student allows her thoughts to go to unskillful places, that too may trigger the SNS. For some people, mindfulness can actually trigger anxiety! They may be already too mindful and any increased awareness of sensations can make them hyper-vigilant.
Heart rate can be influenced by breath, emotions, thoughts, sensations, and other factors such as diet and lifestyle. In all such cases, however, a slowing of the breath may be helpful.
I hope this helps.
Cheers
Bernie