The smartest socks ever: hacking my running with Sensoria's fitness tracker

One part ankle bracelet, three parts personal trainer


I've recently discovered that running is a deliciously simple and effective way to get fit. In less time than it takes me to commute to my gym, I can experience all the sweaty goodness of a stress-relieving workout and take a tour of San Francisco's beautiful neighborhoods. But I made the amateur mistake of assuming that since running is simple, it should also be easy.

Unlike every other form of workout I've tried, from yoga to weightlifting, I didn't bother to get a coach. And, after four months of regular running, my terrible technique caught up with me and the chronic pain has left my running shoes collecting dust in the closet.

My story is all too common among the millions of aspiring health nuts who use running as their entrance into fitness. One experimental study published last year in the Orthopaedic Journal of Sports Medicine found that roughly a third of new runners sustain some form of injury in under a year.

There's such a hunger for a tech solution that one device manufacturer, Sensoria raised $100,000 in crowdfunding and another $5 million in investment for a concept smart sock that can detect and improve running technique.

The resulting product is the Sensoria, a $149 anklet device attached to a special running sock. It coaches users with real-time analysis of their foot-striking position and stride. It will be available to its crowd-funders later this year and available to the public in Q1 2015.

I took the Sensoria out for an exclusive spin around San Francisco's famous hills to see if a sock that's priced roughly its weight in gold could be the saving grace of injured runners everywhere.

Sensoria running tracker

The Sensoria itself is a horseshoe anklet that attaches to a special sock via five brass knuckle-like magnets stitched near the lower shin area. Special sensors in the bottom of the sock measure where the foot makes contact with the ground and for how long. The anklet, which contains a CPU that analyzes data from the sensors, is so light that I would forget I had it on. It's discreet enough to go unnoticed on the streets unless a stranger is looking close enough at my feet to see a small hump in the sock.

The real magic is in the smartphone app, which displays a detailed heat map of where pressure is being placed on your foot, along with detailed statistics on foot contact time, cadence, steps taken, stride length, and speed (Sensoria also makes a shirt with an embedded heart-rate monitor, which works in tandem with its software).

Sensoria foot heat map

Even to a proud data nerd, all these statistics can seem overwhelming. So, Sensoria interacts with the user through an automated coaching assistant that yells out simplified advice when it detects poor form. "You're failing to land on ball," it chirps in my ear, if I fail to heel-strike consistently for more than 30 seconds. If my stride becomes irregular (a mistake that can result in debilitating injury), Sensoria chimes in with a "Pick up the pace!" command.

To appease both perfectionist marathon fanatics and newbie joggers, Sensoria takes a Swiss-like neutrality to rabid internal debates within the running community on proper form. Its default, for novice users, recommends landing on the ball of the foot — known as "forefoot striking". Experts have the option to switch to heel striking and can precisely narrow in on their preferred cadence per minute.

For the sake of experimentation, I left on all the defaults for my initial run up San Francisco's famous fog-covered trails.

Sensoria running tracker

I took Sensoria out for an late evening, 4-mile run up one of San Francisco's famous routs, Bernal Heights. Two miles of flat street running and 400 feet of winding upward elevation on a paved trail let me see how the smart sock could handle all sorts of environments.

Immediately, my sock told me my running technique was lacking; I was still on my home block when I triggered its first warning that I was failing to properly land on the ball of my foot. After a few minutes of frustrating correction, I eventually got up high enough on my toes to quiet Mara, my lovingly-named virtual coach.

Unfortunately, half a mile later, I was duped into believing that I had instantly become the image of running perfection. The anklet had become unhinged: without notification, it just stopped giving advice. I spent the next 3 miles nervously checking my phone every time it went quiet, even though I had eventually adjusted my sock to keep it reliably paired.

Aside from this design bug, Sensoria performed admirably on flat streets. Running is perhaps uniquely prone to poor form because it’s so repetitive. Unless you have the motivation of Lance Armstrong or consume a bathtub full of caffeine, it's near impossible for mere mortals to maintain concentration for 10,000+ monotonous steps.

On hills, Sensoria struggled. Even though it can keep track of elevation, it doesn't quickly adjust its advice. During the hardest part of my run on a 30-degree incline at base of Bernal, Mara blared at me to maintain the same cadence I kept on flat streets.

The Sensoria did eventually adjust to the ascent, but only after a half-mile of badly timed instruction — a rather unpleasant experience when I would normally just quietly enjoy the view of San Francisco rooftops. I encountered the same frustrating bugs running back downhill and when I had to jog in place during red lights. Despite the less-than-perfect performance, Sensoria did live up to its promise. I feel like my technique improved and I enjoyed knowing that I was on track to a less injury-prone run.

Sensoria running tracker

For really serious runners, likely the target demographic for this, Sensoria is more likely to supplement a coach than to completely replace one. I took the wearable sock to my own technique guru, Kelly Starrett, famed Crossfit mobility expert and author of the upcoming Ready to Run.

As an initial diagnosis exam, he had me ditch my shoes and run barefoot; it's a strategy he says naturally orients humans to run with proper forefoot striking and helps identify the best possible technique that they are currently capable of.

"You don't need to spend $150 on a sock, you just need to run barefoot for two minutes," he said.

Barefoot running exposed the limits and promise of Sensoria. In only a few seconds, Starrett noticed that I place a dangerous amount of weight on the outside of my foot (I "prance", in his less-than-kind terminology).

During my initial run around San Francisco, I had unwittingly gamed Sensoria's forefoot-striking system by keeping high on my toes, but this change was unlikely to solve the chronic pain caused by more fundamental problems. Apparently, I compensate my poor leg flexibility by bowing my feet outwards, which translates into terrible technique.

For right now, Sensoria can only sense poor technique coming from ball or heel striking, not overexertion on the inside or outside of the foot ("pronation"). Heapsylon tells me they hope to add this feature in the future.

Still, Starrett is bullish on Sensoria's technology. Once I fix my underlying physiological issues, the smart sock will ensure that I maintain fidelity to my hard-trained technique through the entire run. He's also excited that Sensoria could be applied to all kinds of sports, from basketball to rowing, as proper foot placement is a secret sauce to injury-resistant exercise.

Indeed, the unintended applications are rather expensive. I had the idea that Sensoria might be the ultimate shoe shopping aide, since it can sense which shoes naturally fit my foot while walking.

So, I secretly tested out the Sensoria with running shoes and a pair of old Birkenstocks. I wanted to see if their engineering team could see which shoe was easier on my knees without me telling them what I was wearing in each test. Sure enough, they correctly identified the Birkenstock as a "minimalist" shoe, which I had been wearing to ease the pressure on my legs during casual walks around my neighborhood.

It'll be exciting to see what developers and coaches do with new wearable technology when they can get their hands on the latest versions.

Sensoria running tracker

Sensoria enters a crowded market of eager tech entrepreneurs who want to own a slice of the lucrative fitness market. Over the next year, a generation of wearables will make the evolution from simple step counting to advanced biological sensors.

For instance, the upcoming Athos shorts measure effort from major leg muscles to help athletes identify whether they're using the most powerful parts of their body for each movement. The US Open tennis team partnered with e-clothing manufacturer Om Signal on a smart shirt that measures breathing and stress levels.

Even though Sensoria isn't perfect, I'm still going to wear it during runs

Even though Sensoria isn't perfect, I'm still going to wear it during runs. It's worth using even with the bugs, which potentially could be fixed in the public version.

The most exciting aspect of Sensoria isn't what it can currently do but how the next wave of wearables will transform the way we train. Countless runners take up the sport haphazardly, ignoring the collective wisdom of experts that has built up over decades.

As more smart clothing becomes technique-aware, amateurs will instantly be connected to cutting-edge science in an app that packages advice into simple real-time advice. The more data is collected on runners, the better data scientists can engineer advice to inspire the running masses into safe, peak performance.

For now, I'm eager to get back into running and I know I'll need some sort of tech to keep me focused on injury-free technique.

Photography by Josh Lowensohn