A year after we moved to northern California I acquired a pair of shiny new titanium hip joints. There would be no more running for me. But I’m a lucky guy who gets to to bike and hike more than ever amidst spectacular scenery that no-one could fully explore in a lifetime.
Although the osteoarthritis was more advanced on the right side, we opted for bilateral replacement because the left side wasn’t far behind. Things hadn’t felt symmetrical in the years leading up to the surgery, and that didn’t change. There’s always a sense that something’s different about the right side.
We’re pretty sure it’s not the hardware. X-rays show that the implants remain firmly seated, and there’s no measurable asymmetry. Something about the software has changed, but there’s been no way to pin down what’s different about the muscles, tendons, and ligaments on that side, whether there’s a correction to be made, and if so, how.
Last month, poking around on my iPhone, I noticed that I’d never opened the Health app. That’s beause I’ve always been ambivalent about the quantified self movement. In college, when I left competive gymnastics and took up running, I avoided tracking time and distance. Even then, before the advent of fancy tech, I knew I was capable of obsessive data-gathering and analysis, and didn’t want to go there. It was enough to just run, enjoy the scenery, and feel the afterglow.
When I launched the Health app, I was surprised to see that it had been counting my steps since I became an iPhone user 18 months ago. Really? I don’t recall opting into that feature.
Still, it was (of course!) fascinating to see the data and trends. And one metric in particular grabbed my attention: Walking Asymmetry.
Walking asymmetry is the percent of time that your steps with one foot are faster or slower than the other foot.
An even or symmetrical walk is often an important physical therapy goal when recovering from injury.
Here’s my chart for the past year.
I first saw this in mid-December when the trend was at its peak. What caused it? Well, it’s been rainy here (thankfully!), so I’ve been riding less, maybe that was a factor?
Since then I haven’t biked more, though, and I’ve walked the usual mile or two most days, with longer hikes on weekends. Yet the data suggest that I’ve reversed the trend.
What’s going on here?
Maybe this form of biofeedback worked. Once aware of the asymmetry I subconsciously corrected it. But that doesn’t explain the November/December trend.
Maybe the metric is bogus. A phone in your pocket doesn’t seem like a great way to measure walking asymmetry. I’ve also noticed that my step count and distances vary, on days when I’m riding, in ways that are hard to explain.
I’d like to try some real gait analysis using wearable tech. I suspect that data recorded from a couple of bike rides, mountain hikes, and neighborhood walks could help me understand the forces at play, and that realtime feedback could help me balance those forces.
I wouldn’t want to wear it all the time, though. It’d be a diagnostic and therapeutic tool, not a lifestyle.