In the third stage of this meditation practice we let go of the counting and simply follow the breath as it flows in and out. This is the Mindfulness of Breathing proper, and if I were forced to introduce the Mindfulness of Breathing practice in two minutes then this is what I’d teach — simply paying attention to the sensations of the breath.
However, by saying that I don’t want to devalue the earlier two stages, which are important aids in helping us to practice effectively in this stage of the practice and important practices in their own right.
Here’s an outline of the practice so far:
Set up your posture, as described in the posture guidelines, developing awareness of the body and relaxing as best you can.
Then, becoming aware of the breath as the central experience within the body, begin counting after each out-breath, counting in cycles of ten breaths. When you notice the mind wandering, gently bringing it back to the breath. Notice the gently relaxing quality of the out-breath.
Moving into the second stage of the practice, begin counting just before each in-breath, again counting ten breaths before starting over again at one. Notice the gently stimulating quality of the in-breath.
When you feel ready, move onto the third stage.
In the third stage of the practice, drop the counting, and just follow the breathing coming in and out. Pay particular attention to the transitions from an in-breath to an out-breath, since those are the places where you’re most likely to become distracted.
See if you can notice the breathing as a continuous process — not as a series of in-breaths and out-breaths, but as a never-ending stream of sensation connected with the movements of the body, and the sensations of the air flowing into and out of the body.
You can listen to an MP3 guided meditation that will lead you through the first three stages of the practice by clicking on the player below:
If you’ve been working methodically through this practice you know the score by now. Try doing all three stages for a few days. Practice them every day, if possible, and get to know them well.
Watch out for any tendency to want to skip over one stage (maybe because you don’t like it as much as the others). Each stage has its own special function, so remember to do them in the correct order.
You might want to make your meditation a little longer now, perhaps five minutes per stage, making fifteen minutes.
Shunryu Suzuki, the famous Zen teacher who founded the San Francisco Zen Center and who was a major influence on Western Buddhism, talked about “the gaining idea.” This rather awkward but incredibly useful phrase points to the problem that arises in our practice when we’re hungering for results. We want be enlightened right here and right now. Or we simply want to rush on to learn the whole practice so that we can check that off our list of things to do. The gaining idea is a major hindrance to developing skill in meditation.
As Suzuki Roshi said, “When a gaining idea arises in our practice, it is a sign that our practice is in trouble.” The reason for this is that we’ve actually incorporated our restless, grasping mind into our meditation practice. Our practice has been taken over by the mind that craves, yearns, and tries to appropriate results without following the path that leads to those results.
These attitudes of grasping, craving, and greedy hunger are the very things that cause us suffering in the first place. Because we suffer we want to meditate, because meditation is the antidote to craving and suffering. And then what happens? Our craving takes control of the meditation! It’s as if the antidote to the poison itself accidentally becomes contaminated with poison!
It’s useful if you learn to recognize this gaining idea, this notion that somehow your best interests will be served if you rush through the practice. That notion is false. Meditation is about letting go of grasping so that we can experience freedom. So start doing that now by deciding that you’ll pause where you are right now, and that you’ll explore the stages of the meditation practice and really get to know them before you move on to the next stage.
As part of that exploration come back to this section and read a bit more about the issues that can arise in this stage of the practice.
Perhaps this is a good time to remind you of your body. I’ve emphasized that it’s important to set up your posture at the start of a period of practice. Doing this provides you with better conditions for meditating.
It’s like making sure, when you’re building a fire, that your kindling is stacked just right and that your matches are dry, so that you’ll end up with a good blaze instead of a pile of smoldering wood and a bad temper.
But when you take your attention away from your posture in order to be more aware of your breath, you’ll often find that your posture starts to drift. You might find that some parts of your body start to sag, while others become tense. And these changes lead to mental and emotional changes.
The tension in your shoulders might be related to some anger you’ve started to experience. The sagging in your spine might be related to a feeling of despair that’s crept in. If you relax your shoulders, the anger will start to disappear again. If you straighten your spine, you’ll start to feel more confident again.
As you become more proficient at meditation, you’ll learn that you can periodically take your attention away from your breath for a split second in order to check your posture and make minor corrections. You’ll get so good at doing this that you’ll be able to effectively keep a continuous awareness of your breath.
Remember learning to drive? You probably found that at first you’d take your attention off the road to change gears and when you took your attention back to the road (several long seconds later) you’d find that you’d drifted off towards one side or that a red traffic light had mysteriously appeared from nowhere. Later, you’ll have found that you were able to change gears without significantly taking your awareness from what was going on around you.
The same thing happens in meditation – we learn to deal with the seeming complexity of managing our posture and what we’re doing with the focus of our attention – elegantly and even effortlessly. A good way to start practicing this skill of monitoring your posture without disrupting your practice is to check and correct your posture in between stages.
You might want to do this every time you move from one stage to another. Later, you’ll find that you can integrate monitoring your posture into your practice in the way that I’ve described.
While stage one of this meditation practice helps to develop more calm (by emphasizing the qualities of the out breath), and stage two helps to develop more energy and awareness (by emphasizing the qualities of the in breath), the third stage emphasizes both the in breath and the out breath equally. This helps us to blend the calm relaxation of the first stage with the energized awareness of the second stage.
In our meditation practice we are ideally developing a sense of energetic calm awareness, or a calmly energized awareness. While doing stage three you can be aware of the constant oscillation between the calming out breath and the energizing in breath, and allow the qualities of the out breath and of the in breath to permeate each other.
Modifying an analogy the Buddha himself used, you can think about making dough. When you’re making dough, what you’re doing is taking two contrasting substances – a wet one and a dry one – and combining them together in a perfectly balanced blend.
If you have too much water, then you’ll have a sticky mess, while if you have too much flour, you’ll have a dry, cracked ball.
Get the proportions just right, and you’ll have dough that is perfectly pliable and workable. (The Buddha’s analogy involved a “bathman or bathman’s apprentice) blending soap powder and water — presumably the Buddha was more familiar from his earlier life with bathing in luxury spas than he was with baking).
Just as the right balance of flour and water (or soap-powder and water) produces a pliable mixture that can be used appropriately, this stage of the mindfulness of breathing meditation practice helps us to develop pliability of mind; to get our minds into a calm and energetic state where we can work to develop a much greater degree of concentration.
If the first two stages have gone really well, letting go of the numbers can allow us to develop a deeper and more balanced concentration. However, if we haven’t managed to develop enough calmness in the first two stages, then it’s easy to get lost in the third stage.
This often happens because the counting has been acting as an anchor for our awareness: it stops us from drifting too far away from the breath. So if we let go of the counting we can often float off into distraction.
One way to retain an anchor while letting go of the numbers is to use a physical sensation in the body as an anchor. I sometimes use the physical sensations in my hands in the same way as I use the numbers.
Sometimes at the end of every out-breath I take my awareness to my hands in order to keep me grounded. I use the sensations in my hands much as I’d use the numbers.
The physical anchor is a more refined anchor than the counting because it’s non-verbal — it cuts down on the amount of thinking, so that your mind can develop a deeper level of stillness.
Other times I maintain awareness of my hands throughout the cycle of each in-breath and out-breath. When I breathe in there’s a sensation of rising in the body and so I have a general sense of the gap between the hands and the breath widening. In each out-breath there’s a feeling that the body is sinking, and so I get a sense of the connection between the hands and the breath narrowing. So I notice the connection between the hands and the breath, and this helps keep the mind from wandering off.
Partly I think this works because it makes the practice more interesting. But partly I think it’s something to do with introducing a “stretch” into the practice. What I mean is that I’ve noticed that when my mind stretches to accommodate two separate sensations it seems to calm down very quickly. I can’t explain this, but I offer it as a tool that might be useful.
Other “stretches” involve being aware of the space outside my body while focusing on some inner sensation (like the breath), and being aware of sounds outside of myself while following some inner sensation.
You might want to play around with this idea of creating a stretch in your awareness and see what happens. Just notice two very different and geographically separate sensations, and pay attention to both simultaneously. And notice what the result is.
We talk about “trains of thought.” You can think of these as being like real locomotive trains that pull into a busy station and then go rattling off. Most of them don’t go anywhere that we particularly want to go (most of them are to do with worrying, getting angry, running ourselves down, etc). But our mind is like a little kid that’s very restless and curious, and keeps going through the open doors into the carriages.
Before we know it we’re miles away from where we wanted to be (in dangerous territory, often!), and it takes us forever to get home.
By learning meditation you can learn just to watch the trains pulling up and pulling away, being aware of them and choosing not to get into them.
Are there any trains we want to get into? Yes. Some thoughts can be useful, if they are thoughts that guide us toward our immediate experience. For example, we can say to ourselves things like “Staying in the moment … there’s just this moment.” Thoughts like that take us deeper into our meditation.
One difference between useful thought trains and those that take us into distractions, is that when we’re reflecting (as opposed to being distracted), we know what we’re thinking and why, and what effect those thoughts are having). By contrast distracted thoughts are like dreams — we don’t know we’re in them until we “wake up.”
But it can take a while to recognize which thoughts are useful and at first it’s not a bad idea simply to treat all thoughts as distractions and to let them all depart from the station of the mind while you “just sit” on the platform.
There’s another way that the third stage of the mindfulness of breathing meditation, in which we drop the counting of the first two stages and simply follow the breath flowing in and out, is a progression from those two stages.
The progression consists in sensing the continuity of the breathing process, through having an unbroken awareness of the breathing rather than in having an awareness of individual breaths.
When we’re counting out-breaths (as in the first stage of the meditation practice) or counting in-breaths (as in the second stage) there’s an inevitable tendency to experience the process of the breathing as being chopped into bits. There’s an in-breath. Then an out-breath. Then another in-breath. Then another out-breath. We may acknowledge pauses between the in and out phases, so that we mentally chop the breathing into four parts: in / pause / out / pause.
Now actually the breathing process isn’t quite like that. It’s not really divided into discrete parts. When you watch the breathing closely in meditation you’ll see that the in-breath shades into a feeling of fullness, which then shades into the release of the out-breath. Then the increasing sense of emptiness at the end of the exhalation shades into the beginning of the next in-breath. There are no distinct beginnings or ends. There’s just one continuous process that changes its character over time. It’s much like looking at a rainbow. There are different colors, but when you look at where one color shades into another you’ll see there are no distinct transitions.
We’re practicing mindfulness of breathing, not mindfulness of breaths.
When we experience the breath as chopped up then there’s a tendency for our awareness itself to become discontinuous. We actively experience the in-breath, then the mind goes a bit floppy for a moment, then we pay attention to the out-breath, then the mind goes a bit squidgy again. Somewhere during the times when the mind is taking a little vacation from vividly noticing the breath it decides instead to get absorbed in some thought or fantasy, and we don’t have the mental sharpness to stop it from going on a little (or perhaps a long) wander.
When we get to the end of the second stage and stop counting we have the opportunity to experience the wholeness of the breathing rather than the chopped-up-ness of in-out-in-out. And so our awareness itself becomes more continuous. We’re less likely to get distracted. The mind becomes more attuned to the subtler sensations where the breath is changing from an inhalation to an exhalation, and vice versa. And we develop a very pleasant sense that we have a continuous thread of awareness running through our experience.
So practically, what this means is that we follow the sensations of the breath as it flows in, noticing the sensations of movement becoming subtler as the sensations of fullness are becoming stronger, noticing the “cresting” of the inhaling as it releases from fullness into the emptying of exhaling, noticing the sensations of exhaling becoming stronger as the body moves faster and as the exhaling happens more slowly, bottoming out into an increasing sense of emptiness, until the emptiness gives way to a sense of filling. And so on, and so on. It’s actually hard to put this in writing because for the sake of clarity in writing I have to use commas and periods, which suggests a succession of discrete experiences rather than an ever-evolving transition within one single experience, which is the process of breathing.
Another approach would be, next time you’re following the breathing (and maybe that’s right now) seeing if you can notice any absolute boundaries and discontinuities within the process of the breathing. I think you’ll find there are none, and that as your sense of the breathing becomes more continuous, so too does your sense of the continuity of your mindfulness.
The great hypnotherapist, Milton Erickson, told a story about how one day, when he was a boy, a riderless horse wandered into the farmyard outside his home. Milton had never seen this horse before, and had no idea where it lived, but very soon he had the horse back where it belonged. How did he do this?
Well, he sat on the horse’s back, got it to start walking, and then every time they came to a turn in the road, he paid attention to the almost imperceptible movements of the horse’s body that told him where it wanted to go. And once young Milton had sensed in which direction the horse wanted to head in, he encouraged it to do so. It turned out that the horse knew its own way home, and all Milton had to do was give it a little gentle guidance — or encouragement to trust its own instincts.
It’s similar with our breathing. I’ve said that in the mindfulness of breathing practice we’re not controlling our breath. On the other hand I’ve also suggested that you can use deep breathing, or breathing into the belly, or breathing into the upper chest, etc., as ways of altering your state of mind. This might sound contradictory, but it’s not really. When we change the pattern of our breathing, we don’t have to exert any control. We can gently guide the breath without controlling it, as Milton did.
Had Milton tried to tell the horse where to go, he’d never have got it home. Horses, after all, are trained to follow orders. Instead he used a more subtle technique of being aware of where the horse wanted to go, and then reinforced that desire with some gentle guidance. The horse soon got the idea.
We all are riders of horses, in a way. Our breathing is generally under the control of subconscious processes, and it has to be said that our subconscious, by and large, does a pretty good job of keeping breathing. The subconscious rarely fails to carry out its tasks, which is more than can be said for our conscious minds (how often do we go upstairs to get something and then forget by the time we get there what it was we wanted?). So let your subconscious do what it’s good at.
When you want to change your breathing, say by breathing into your belly more deeply, then all you really have to do is to take your awareness into your belly to give your subconscious a gentle hint, and then let it do the work. In this way, we gently guide our breath rather than control it.
The fourth stage of this meditation practice helps us to have greater focused attention. You can learn about that here.
You can also learn more about this meditation practice in my book, Wildmind: A Step-by-Step Guide to Meditation.
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I've been reading widely about meditation, and always come back to Wildmind because it's so straightforward and clear. So thank you for that!
But I've become very confused about what to do about thoughts in meditation. I have a very analytical mind and as soon as I start observing thoughts I go off into immense detail about how useful they are, how emotionally charged, what I should be doing with them etc. etc. - and quickly find I've left my breathing far behind, not just with the thought train but with operating the whole railway network!
Early on in my meditation experience (I've been meditating daily for about eighteen months now) I used to feel a thought bubbling up and just not go there, keeping focused on the breath. I grew concerned because I thought suppressing thoughts was unhealthy. Now I find I'm alert for thoughts all the time; I'm breathing happily and then suddenly 'hey, no thoughts! I wonder when the next one will come along?'
I'm really not sure where to go with this. Any advice would be really, really welcome!
With many thanks for your wonderful site,
Helen
Hi, Helen.
Just keep letting go of your thoughts. When you get caught up in them, just gently return to the breathing. You're not "supressing" thoughts by doing this; you're simply not putting energy into them. The thoughts vanish on their own. Suppression, in standard Buddhist terminology, is something completely different -- it's forcing thoughts out of your mind by forcing your attention onto an object like the breathing. It's regarded as a last resort. Some Vipassana people sometimes talk about doing anything in meditation as "suppression" but this is a misuse of the term.
When you get a thought like ‘hey, no thoughts! I wonder when the next one will come along?’ then just do the same thing. Let the thought pass through. It's no different. It sounds like you're regarding this kind of thought as being a big deal, or perhaps as some kind of failure. It's neither. It's just a thought. It seems you may be clinging to the idea of not having any thoughts at all, and since it's unreasonable to assume that your thoughts will cease (unless you go very deep indeed into meditation) it would be more helpful to appreciate the calm that is there, while it's there. Try smiling when you notice that kind of thought. And see if you can relax your attitude a little. Find a spirit of playfulness and appreciation and love.
Greetings,
I am an infant when it comes to meditation but have been experiencing some very unusual sensations. Today as I meditated I began being pulled to the left. I allowed the steady movement and put up no resistance. It was pretty cool but it has left me wondering if it means anything. I eventually was leaning to my left until I felt the pulling subside. I also feel waves as if I am in the ocean. Can you please shed some light on what this all means??? If it means anything at all :-)
Thank You!
These kinds of experiences (samapattis) are fairly common in relative beginners, and they tend to arise when the mind is starting to settle down. They're not of any significance in themselves, and in fact becoming interested in them will prevent you from going deeper in meditation. They seem very similar to the kind of thing people experience under sensory deprivation, and I think of them as mild hallucinations that arise because we're not used to the mind being calm. So I'd suggest not playing around with them and instead just keep returning to the meditation practice.
You may later find that a different quality of experience emerges. These experiences (nimittas) are more related to the meditation practice itself, have an esthetic quality to them, and will help you get more concentrated if you pay attention to them. In my experience people who are prone to samapattis are also prone to nimittas.
I meditate everyday in the morning for 1.5 hrs.
Its peaceful. Its magical.
But after the meditation I get an immense urge to lie down and fall asleep.
I dont feel tired.
Sleep just comes to me.
Is it normal? I have been meditating for the last one month.
Sometimes even in the evening I meditate for an hour.
When I open my eyes, everything is blissful.
But it always ends in sleep.
Please help.
Thanks
What are you doing in your meditation practice, Kumar? What are you paying attention to? How are you sitting?
Strange though it may seem I found this advice very challenging. My life is difficult at the moment and the thought of relaxing and finding a spirit of playfulness honestly seemed so impossible I found it deeply distressing - it's what I want more than anything (I am by nature a playful, creative person) but it felt so far away. That rang big alarm bells for me as someone who struggles with depression and anxiety. (And I admit I may have yelled at the screen, somewhat unreasonably!)
To cut a long story short, your kind and innocuous comment showed me just how bad things have become, and I've been able to work on it.
I've stripped the complications out of my meditation practice and I'm just enjoying the calm when it happens and letting the thoughts drift off and do their own thing without troubling me. I imagine enclosing them in a little bubble and then I softly blow them away with a little wave. It's so, so much better than all that analysis!
It sounds so simple to advise someone to be more playful, but it can be both challenging and very, very important. Thank you.
Good morning! I wanted to share some of what I experienced this morning. I feel as though I have finally had the experience in stage three that I have been reaching for. I have not allowed myself to move forward to stage 4 until progress has been made, and it's been a disappointing couple of weeks. Today, rather than focusing on my hands as an anchor, I searched for my heartbeat in my chest. Once I found it's rhythm, it sort of took over. My whole body seemed to sway slightly with my pulse and I could feel it through my whole awareness. My breathing became more natural, and my usual internal chatter was gone. I felt myself slip into a sort of trance state and my conciousness felt like it was floating above my body. I began to see and feel these warm ripples of light moving upward across what seemed to be my field of vision, but maybe it was more my field of awareness. They weren't a focus or a distraction, they were just there. I had a couple of random thoughts sort of flit though my mind, but it was as if I was in a room with an echo and those thoughts came from somewhere else in the room. Then, the lights faded away, and my mind reattached to my body little by little. I am trying not to be carried away by my positive feelings about what happened, because then I will be trying too hard to make it happen again. What is this experience? Is it still categorized as mindfulness meditation? The focus on my breath is what got me there, but I wasn't even really aware of my breathing toward the end. The after effects are quite lovely as well. I feel so relaxed and have a sort of soft tingly feeling throughout. With years of practice, is this something that people can have happen every time? Thank you for any insight on this.
Hi, Meghan.
Sorry for the delayed reply, but in the last few days since you've posted I've had a family outing, an illness, and a day of intense work.
The experience you describe sounds like an access concentration state that's gotten a bit unbalanced. There are a couple of different kinds of "unusual" phenomena that can appear in access concentration -- which is where the hindrances are starting to calm down and the jhana factors (roughly put, calmness, joy, energy, concentration) are beginning to emerge. One type is a bit "trippy" and a bit ungrounded, and that's what your experience sounds like -- in particular the detachment from the body and your description of this as a "trance" state. There are positive aspects to this kind of experience, obviously (the calmness, for example) but spiritually they're not very useful. I wouldn't suggest trying to recreate the experience. Often people describe flowing patterns of light, etc. Sometimes there are slightly unpleasant or disturbing sensations, which you don't seem to be describing. These kinds of experiences tend to be more common in people who haven't been meditating for very long.
The other kind of experience (called a "nimitta") that can arise around access to the beginning of jhana is superficially a bit similar, but more grounded. Nimittas can be images or sensations in the body, but they help us go deeper into jhana. They tend to be very stable, still, and esthetically pleasing.
People who experience the first kind tend to experience the second kind as well, so I'd suggest steering your attention so that it's more rooted in your physical experience. Stay in touch with the body. if you notice the "trippy" stuff arising, just note it and keep on with the practice.
Sorry if this sounds like a buzz-kill! You're definitely moving in the right direction, and you're close to jhana. The problem is you're taking a little detour, by the sounds of it. I stress the "by the sounds of it" because it's always hard to interpret other people's meditation experiences, especially when we're not face to face.
Good morning Bodhipaksa. I just realized that in my above message, I neglected to specify that I was writing to you! My apologies, and I am very much looking forward to your response.
Ps. I'd also like to add that, surprisingly, my experience from yesterday's meditation was closely repeated today! Although, not quite as deep, and the light pattern was different. Less regular and rhythmic. I noticed that my breathing becomes more shallow in that stage.
Good morning. Thank you for you response. I did find it helpful, and made an attempt to redirect myself this morning. I tried again to focus on my hands, and it did seem to get somewhere. I began to feel my heartbeat throughout and the gentle sort of sway that comes with it. I made an effort not to get lost in it and kept my focus on my breath. For a moment those light ripples came again but I managed to send them packing. After a few minutes, I began to "see" this light in front of me. It was this soft oval glow, like a candle flame. As strange as this may sound, it felt like the light was looking back at me. It was only there for a moment, because then the recording started wrapping up and broke my focus. I think maybe I should move on to Stage four tomorrow? I definately felt that I could have gone deeper with more time.
This whole process is getting easier now. I am no longer fighting with the need to control my breath and am having an easier time keeping my internal chatter at bay. I took a day off from meditation until I heard back, and noticed a difference in myself. I was less patient with my kids, and more tired at the end of the day. I am asking myself what I am hoping to get out of this practice. I can't really answer that very well. I think I just want to move forward through life happier, more peaceful. And I am! I have been less caught up in the daily annoyances of life and feel an overall outpouring of happiness and love for my family.
What do you think of the little light that was with me today? I definately was more grounded and felt like I was scratching at the doorway of something... Am I ready for stage 4? I suppose I should read it now. Thank you in advance for your response and guidance. Have a happy day.
Hi, Meghan.
That soft glow looking back at you sounds much more like a nimitta. Yes, I'd definitely suggest you move on to the fourth stage. The refinement of focus in that stage may well be helpful. In the long term though you'll probably find that you don't really need to be dependent on "stages," and that your meditation simply has its own internal dynamic, shaped by an awareness of what works and what doesn't work. If the soft light, or something like it, reappears, then pay attention to the nimitta along with the breathing, and see what happens.
It's going to be important not to "try" to make anything happen. Any kind of grasping beyond a very mild effort to stay with the practice is going to be unhelpful, and it's useful to think more in terms of relaxing into the practice.
All the best!
Thank you! I have noticed that I have moved through the stages a little more at my own pace, loosely guided by your recording. I have been going in with no expectations, and accepting the fact that I may have an "unsuccessful" session each morning. Things seem to be progressing and I am happy about that. I think it is no coincidence that we focus on the hands while we avoid "grasping" at anything. We focus on the breath while not controlling it and focus on the hands while not reaching. So what's next? To focus on the nimitta while not letting go of our awareness? Am I oversimplifying? Again, I am so grateful to have some guidance in this. Is this light possibly me looking at myself? This is giving the term "love and light" a more literal meaning. =)
It's hard to say what the next stage would be for you. It's possible to move more deeply into jhana, letting go of thinking (that's second jhana), then becoming more absorbed in the feeling of joy (that's third jhana), and then moving closer in to the object of focus so that even joy is left behind and there's a deep peace (that's fourth jhana). That's the samatha route. It's also possible to simply be with your experience and let go of the sense of there being an experiencer and a thing that is experienced. That's the vipassana route (or at least that's one vipassana route). These are not mutually exclusive routes to take, and in fact both are to be encouraged. But I'd suggest that you mainly focus on deepening your experience of samatha by developing more experience of jhana, and from time to time relax so deeply into your experience that the experiencer/experienced division falls away.
It's kind strange something that is happening to me: whenever I sit and start focusin, it's seems that the middle part of my chest, just below the heart (and I am sure it's not the heart) starts pumping in a strong, powerful way. Can anyone relate to this? Thanks :D
Hi, Felipe.
One of the things that can happen in meditation is that as the mind settles we start to notice subtler sensations in the body. There are a lot of nerves in the area you're talking about: there's the vagus nerve running all the way down to the intestines, and also the celiac (solar) plexus. And there are of course lots of blood vessels. It's possible that you're picking up on some rhythmic activity connected with those nerves or vessels.
Sensations like these have no inherent value, but since they tend to be noticed when the mind is becoming more still, they can be seen as signs ("nimittas" in Sanskrit) that we're heading in the right direction. So just notice them and recognize them as a good sign.