Listening to the Signal, Not Chasing the Number

By Robb Erskine

Have you ever really looked at your Apple Watch and the health metrics it quietly collects day after day? Not just glanced at your rings or heart rate, but actually paused to wonder what all that data might be telling you. I hadn’t—at least not in any meaningful way—until one day I did.

Out of curiosity, I started poking around the Health app, reading about some of the metrics I’d been mostly ignoring. One in particular caught my attention: heart rate variability. I didn’t know much about it beyond the fact that it seemed to fluctuate a lot, and that it had something to do with stress and recovery. That was enough to send me down a short research rabbit hole.

I learned that heart rate variability, or HRV, isn’t about how fast your heart beats, but about the variation in time between beats. That variability reflects how adaptable the nervous system is—how well it shifts between mobilizing for action and recovering afterward. What makes HRV especially useful isn’t any single number, but the pattern it forms over time. It can offer a subtle signal of how the body is responding to cumulative stress, recovery, and daily demands.

To make sense of what I was seeing, I needed a simple way to interpret the HRV metric Apple Watch uses. Apple Health reports HRV as SDNN (the standard deviation of the “normal-to-normal” intervals between heartbeats), measured in milliseconds. 
And importantly: HRV is highly personal—what matters most is your trend and your baseline, not someone else’s number. 

What intrigued me wasn’t the promise of optimization or performance gains. It was the possibility of insight. HRV seemed like a way to better understand capacity—how my nervous system was actually experiencing the way I was working and living, not just how productive I appeared on the surface.

Three months ago, I decided to start paying closer attention. Not to chase higher numbers or “fix” anything, but simply to observe. I treated HRV as information, not a score, and began looking at it alongside the rhythms of my calendar and the structure of my days.

At first, the data felt noisy. Daily readings bounced around without obvious explanation. Some mornings the number was higher than expected after demanding days; other times it dipped when I felt fine. It wasn’t until I stepped back and began looking at trends over weeks—rather than days—that patterns started to emerge. This was especially revealing when looking at the patterns for a month and for 6 months.

When I overlaid those trends with my calendar, the story became clearer. Weeks filled with back-to-back meetings, emotionally heavy conversations, and little recovery time were often followed by sustained dips in HRV. The effect wasn’t immediate; it showed up a day or two later, once the load had accumulated. Interestingly, it wasn’t the longest days that had the biggest impact—it was the most fragmented ones. Context switching, decision density, and relational intensity mattered more than sheer hours.

I also noticed what restored me. Blocks of uninterrupted deep work, even when cognitively demanding, were often followed by stable or improving HRV. So were days that included space for reflection, movement, or simply fewer transitions. Over time, another pattern became clear: days when I intentionally made room for my creative hobbies—woodworking and art—had a noticeably regulating effect as well. These activities required focus without urgency, engagement without pressure. They gave my nervous system a different kind of input, one that was both absorbing and restorative, and their impact showed up not just in how I felt, but in how my HRV trended over time.

With that awareness, I didn’t overhaul my schedule overnight. Instead, I made small, intentional adjustments. I added buffers between meetings. I blocked recurring time for deep work and protected it. I became more selective about stacking emotionally demanding conversations on the same day. And when I noticed early signs of strain—both in the data and in how I felt—I treated that as information, not failure.

Over time, my HRV trends stabilized. More importantly, my experience of my work changed. I felt less reactive, more present, and more able to make clear decisions under pressure. The data didn’t tell me what to do; it helped me listen more carefully to what my system was already saying.

That experience reinforced something I believe deeply: sustainable performance doesn’t come from pushing harder. It comes from understanding capacity, honoring recovery, and designing our days with intention. HRV was simply the mirror that made those patterns visible.

The goal was never to optimize my nervous system. It was to learn how to work with it.