Welcome to Stretch, your guide to experimenting with your mental, emotional, and physical performance. Guaranteed to teach you something new about your mind and body.

⏪ Last edition, we spoke about how focus is a biological mechanism you can control—not some elusive, uncontrollable state. Catch up on that here.

⏩ Today, we’re talking about Interoception, your eighth sensory system, and how training your interoceptive capacity will help you manage stress and other emotions.

Interoception—learn to (literally) listen to your heart

I climbed up a 4,000m (13,000 ft) mountain last week: the Gran Paradiso, the highest peak in the Alps entirely within the Italian region. It took us about 4 hours to make it up there from base camp at 2,350m (7,700 ft), leaving at 5 in the morning, with snow crampons on our boots and attached to each other with ropes.

It’s fascinating to observe where the mind goes when the body is put in such unusual circumstances.

Even though hiking up a snowy mountain in summer is my idea of fun (I was there with my 68 year-old mom so I guess I know where I get it from), there’s a lot of mental static that comes with it.

As soon as I’d spot my mind going somewhere unproductive (“should’ve worn that extra layer”) or to the future (“can’t wait for my hot shower”), I’d tell myself “nope, stay here!” and focus on my body: the feeling of my pounding heart, the heaving of my chest, the coldness in my fingers, the tightness of my boots. I’d mentally go from the tip of my toes to the tip of my nose, scanning my body for any tension.

This act / art of tuning into your body sensations has a name:

Interoception.

Our eighth sensory system

Interoception is considered our eighth sensory system and is defined as feeling and becoming aware of our inner body sensations. Some common interoceptive body signals are heart rate, breathing rate, muscle tension, temperature, tickling sensations, and so on.

Our eighth sensory system?

Yep! We’ve all been taught about our five basic senses: sight, hearing, smell, taste, and touch.

Turns out the actual number of senses is a hot topic of debate amongst scientists. Depending on how a sense is defined, the count can range from 5 to over 20 (!!). There’s things like thermoception (sense of temperature), equilibrioception (sense of balance), chronoception (sense of passage of time) and more. Wild!

But so, interoception. Why do we care?

We pay a lot of attention to all the information coming in from the outside (so-called “exteroception”), and comparatively very little to what’s going on inside. And that’s a missed opportunity, because there’s a lot we can learn from our internal body signals.

Research suggests that the more sensitive you are to your body signals, the better you get at dealing with stress and other emotions.

As science writer Annie Murphy Paul writes in her book The Extended Mind:

When you have high interoceptive awareness, you're better at noticing things that cause you stress or discomfort as soon as they start happening. With a clearer understanding of your feelings about a situation, it becomes easier to choose the best way to react or handle that situation. You can make smarter decisions because you're more in tune with your body and emotions. You have control. Low interoceptive awareness means there is little space between your body cues and your reactions. You’re acting habitually, unconsciously, defensively.

Here’s a simple example: I've learned that when I'm doom-scrolling on Instagram, my shoulders tense, my brow furrows, and my breathing becomes shallow. Low interoceptive awareness used to mean I'd look up from my phone 30 minutes later with no idea where the time went, what I'd been looking at, or why I suddenly felt so on edge and insecure. High interoceptive awareness means I spot these signs almost the second I open up the app—which I now rarely do.

The skill of sensing your heartbeats

Okay so how do you strengthen this magical interoceptive capacity?

One very specific and simple way to train your interoceptive skills is by learning how to sense your heartbeats. I first learned about this in Huberman Lab’s episode How to Optimize Your Brain-Body Function & Health.

There’s no real technique to this. It’s as simple as focusing inward and directing your awareness to your heartbeat. You can try it right now. Close your eyes for a moment to shut out all exteroceptive input, and tune into your heartbeat. Can you feel it? Can you try counting the beats?

Note that this does not involve using your fingers to check your pulse on your wrist or neck. It’s about tuning into the sensation of your heartbeat as intently as you can.

Don’t get frustrated if this doesn’t come natural to you. Some people are very good at it, for others it takes some practice. Experiment with different techniques, such focusing on your heartbeat when all the air is exhaled or during a short breath hold, to find what works best for you.

You can incorporate this practice into your daily routine in various ways. I do this mostly during my morning breathwork exercises (resonance breathing at 5.5 breaths per minute or 4:8 breathing) but also at random moments during the day, while reading or walking my dog. If you don't have a breathwork or meditation practice, you can start by simply taking a minute to consciously slow down your breathing and focusing on your heartbeat.

You don’t even need to do this every day. Just a couple of times per week will help you build up your interoceptive capacity very quickly in a way that you just can’t do as easily for any of your other senses (like vision or hearing).

Doing this might feel uneventful in the moment, but trust in the fact that you’re strengthening a very powerful skill that will translate into all areas of your life. “Listen to your heart” is a cliche for a reason, and even has a scientific term: interoceptive cardiac sensitivity. I know we all like research to back things up so here’s another study for you: the ability to accurately perceive your own cardiac signals has been shown to relate to several aspects of emotional intelligence, including emotion recognition, understanding, regulation, and differentiation.

You literally start listening to your heart in moments of stress or discomfort, and notice when you don’t feel quite right about something or someone. That’s gold, if you ask me—whether you’re high up a mountain or sitting down behind a computer screen.

What else I’m up to…