Sympathetic vs parasympathetic: which is better? Yoga teachers should ask “when?”

What are the sympathetic and parasympathetic nervous systems?

Two branches of one system, not two teams.

The autonomic nervous system handles what you don’t have to think about: heartbeat, breathing, digestion, sweat. It has two main branches.¹

The two branches don’t switch on and off in turns. Both run all day. Sometimes one leads a little more, sometimes the other.

The vagus nerve carries most of the parasympathetic pathways.¹ The “window of tolerance” I talk about in the article on the first class. This article is about one thing only: don’t split the two branches into good and bad.

Why do we split them into good and bad?

Because of the way we memorise labels.

Sympathetic comes with the words: stress, racing heart, “fight or flight”. Parasympathetic comes with: relaxed, pleasant, rest. Whichever label sounds nicer becomes the “good team”.

Yoga teachers slide into this even more easily. We teach a lot about rest, slow breathing, Savasana. So the parasympathetic becomes “yoga’s team”, and the sympathetic becomes something to shut down.

That is where sentences come from that sound very expert: “this pose activates the parasympathetic”, “switch off your sympathetic system”. They sound good. Ask one question back and they start to wobble.

Naming it is not explaining it.

In the 300H class I gave a small puzzle: two people each lose 100 million dong. One of them falls apart much more. Why?

The answers came: “different tolerance thresholds”, then “endurance”. Those words only give a new name to the thing we are asking about. So I asked again: why?

Someone added conditions: maybe the other one is used to losing money, maybe she has a billion. I kept the puzzle the same: same savings, same loss.

The clip stops before the class finds an answer. The puzzle is there to practise asking, not to decide why one person gets more stressed.

Ask the other way: when do you need which?

Don’t ask “good or bad?”. Ask “does it fit right now?”.

In class I didn’t repeat the definitions. I changed the situation and asked again. Four situations, four different answers:

• You are doing something very important that needs strong focus.

  ParasympatheticSympathetic

  Sympathetic leads. You need it to put your attention on the task. Not bad.

• A dog is chasing you.

  ParasympatheticSympathetic

  Sympathetic leads, and it should. Stopping to “relax” here is what doesn’t fit.

• You are practising sun salutations, on round five.

  ParasympatheticSympathetic

  Movement needs the sympathetic too. Doing yoga doesn’t mean being calm all the time.

• Practice is over and you lie down to rest before going home.

  ParasympatheticSympathetic

  Now the parasympathetic should lead. The body recovers after effort.

The needle on each card is an illustration for comparing, not a measurement. The dog example is a class question, not advice on what to do when you meet a dog.

I also told a story the other way round. Someone was very relaxed, playing with a dog, and then something bad happened. I didn’t tell it to scare anyone. Only to show: relaxing isn’t always in the right place either.

Good or bad depends on the moment.

The class test: watch the circle, then follow my count

Before that question, I asked the class to try something for about 60 seconds.

The opening question: when you breathe out a little longer than you breathe in, which branch are you working with? The class said: parasympathetic.

Then, instead of explaining more, I started the circle.

1. Round 1, watch the circle. When it grows, breathe in; when it shrinks, breathe out. I reminded them: breathe as normal, no forcing. Eyes open is fine. Stop any time.
2. A question between rounds. If you are made to breathe in deep and out slow again and again, even with “correct technique”, does it feel easier or tighter? Someone said: tighter.
3. Round 2, follow my count. This time I said it plainly: now I am making you breathe. “Take a deep breath in. Breathe out really slowly… slowly… slowly.” A few breaths, then back to normal breathing.
4. Ask again. Having to follow my rhythm, did it feel tighter?

Every command is a pressure.

Watching the circle, each person still knows if their own rhythm is fast or slow. Nobody is in control of them. Following my count, the breath has to chase someone else’s voice, and the word “slow” keeps stretching.

I call that forcing the brain to work. You want someone to settle, and the way you guide becomes one more thing to try hard at.

On the research: many studies find that slow, comfortable breathing goes along with changes in some heart measures, such as heart rate variability (HRV), during the breathing.³ One small study found that breathing out twice as long as breathing in raised the measures linked to the vagus nerve more than breathing in and out for equal lengths.⁴ But taking deep breaths again and again is something else. Breathing too deep and too fast can cause light-headedness, dizziness and a pounding heart.⁵

This was a class exercise, not an experiment. The two rounds differ in many things at once: who leads, how long the rhythm is, who is in control. I don’t conclude how the whole class felt. I just wanted each person to taste the difference before guiding others. On “take a deep breath”, see also Savasana cues for tired students and how to breathe in yoga.

Explaining it properly: mechanism, source, limits

Someone comes back from a singing bowl meditation and says: it was great, so relaxing. Ask why, and they don’t know.

For someone who practises, that is enough. For someone who teaches, it isn’t. “I feel”, “I like”, “I think” are impressions. Not an explanation yet.

Get the mechanism right. Cite the source. State the limits.

Limits are the part people skip most. Who was the study on, how many people, what was measured. One case, one small group, is not an answer for everyone.

To be fair: in that same class, while questioning the group, I said “sympathetic nerve” when I meant vagus and had to correct myself. A slip. Wrong, so fix it, right in front of the class.

One more thing I often say: when you really understand, you can explain it briefly. Needing a great many words is often a sign I don’t understand it yet myself.

A yoga teacher is not a doctor

After learning sympathetic, vagus, window of tolerance, it is easy to feel you know a lot. Hear one story and you talk like a doctor with years of practice. You take on everything.

I said this when teaching 200 hours, and I say it again at 300 hours: I am a yoga teacher, not a doctor.

• Don’t diagnose. Even when you know the names of the conditions.
• Say your limits up front. What you can support, and what you can’t.
• Know when to refer. A serious bone, joint or muscle problem you don’t understand: ask the student to see a doctor, bring back the doctor’s guidance, then talk about what you can support within it.

In class I give you the exact words to say to the student:

Bring scans to a yoga teacher to read, and the teacher takes on the treatment too? I can’t read scans. And even if someone taught me, I wouldn’t want that job just to look knowledgeable.

The same with the nervous system. Don’t say “your sympathetic system is too high”. I can’t see it. Let the student say what they notice, and keep what you see separate from a firm conclusion.

Try it now if you teach

1. Find a sentence you often say with “sympathetic”, “parasympathetic” or “activates”. Ask it: when would this be wrong?
2. Score it on the three criteria above: is the mechanism right, does it promise anything, does it give the student a choice?
3. Next time you guide breathing, offer a rhythm to follow, but say clearly: breathing naturally is fine, stop any time.
4. Try it on yourself first. One round breathing on your own, one round with someone counting for you. Where is the difference?