Interview with Shuvadeep Sarkar, co-inventor of the ReTiSense Stridalyzer


I bought an elliptical machine about five years ago and use it a couple times a week. One of the big reasons I decided to go for the elliptical machine was the almost negligible risk of injury. But recently, I started toying with the idea of adding some running to my routine for the increased activity and high-impact bone strengthening. I did some research on how to get started with running, including the “right” running form. There’s a lot of confusing, even conflicting, information out there. I even found myself with a pair of running shoes in my online shopping cart, but backed out, too scared to pull the trigger. I know running isn’t rocket science, but I started to feel discouraged with the learning curve before even starting. Inertia was pushing me towards giving up and just sticking with my elliptical.

About a week later I was talking with Shuvadeep Sarkar, a former colleague. As luck would have it, the startup he had co-founded, ReTiSense, was developing a wearable running product called Stridalyzer. I was pretty excited after hearing about it, and asked Shuvadeep if he would mind doing an interview for WickedGlitch. The transcript is below.


Shuvadeep Sarkar, co-founder of ReTiSense

WG: First, can you tell us a little bit about ReTiSense?
SS: I co-founded the company in June of 2014 with Anshuman Singh with the goal of building wearable solutions with the sole intention of providing actionable guidance. Since then, we’ve grown to six total employees. We also have many partners in the industry for things like board design, manufacturing, and app development.


Anshuman Singh, co-founder of ReTiSense

WG: What is Stridalyzer?
SS: Stridalyzer is ReTiSense’s first product, a patent-pending wearable stride analyzer. It’s a pair of insoles wired with sensors that can be placed in a runner’s shoes to detect pressure at various parts of the feet. From there, the pressure data is sent via Bluetooth to a smartphone app which, combined with our cloud analytics, can provide real-time feedback on a runner’s technique.

Stridalyzer Poster

WG: How is Stridalyzer different from existing wearables, like Fitbit?
SS: Most current wearables track how much you run, not how you run. They can’t tell you if you’re going to injure yourself or if you’re covering a given type of terrain most efficiently. Stridalyzer places more emphasis on form. It can, of course, still provide the normal running statistics like number of steps taken, distance, speed, calories, etc. But more than that, the insole lets us build detailed stress maps of the feet and knees (through biomechanical models of the human leg). These can be used during and after the run to provide personalized feedback on running technique.


WG: What sort of feedback does Stridalyzer provide?
SS: At the lowest level, the smartphone app can can provide the raw foot and knee stress data over distances as short as ten steps, but many users may not find that immediately actionable during a run. So we’ve built in real-time audio alerts; things like whether you’re over-pronating or supinating your feet, whether you’re over-stressing your heel/arch/knee, and when your foot strike changes. Beyond that, Stridalyzer also provides a high-level form score and performance score for each run, which can be tracked for improvement over time. Lastly, we hope to launch a premium expert advice service next year.

WG: What were some of your big design challenges?
SS: In a wearable one of the big challenges is always battery life. We wanted to be able to run a week on a single charge of a tiny coin-cell battery. We had to find a microcontroller that consumes nanoamperes of current in sleep states, then aggressively use those sleep states. We also used passive piezoeletric sensors rather than accelerometers, which require active power. The other big challenge, kind of unique to our form factor, was where to put the circuitry so it would be safe. The soles of a runner’s shoes take a real beating; they’re subject to tremendous force. Consequently, we settled on putting majority of the circuitry (everything but the sensors) on a thin flap that folds up the interior wall of the shoe.

WG: What sort of hardware is Stridalyzer packing? Will it run Angry Birds?
SS: It won’t run Angry Birds. The main hardware pieces are the coin-cell battery, the lightweight TI microcontroller and bluetooth module, and the sensors. The current prototypes have four sensors, but we’re actively working with doctors and health experts on placement so we may be adding up to two more.

WG: What does it look like?
SS: We’re still experimenting with the insole and flap materials. Our current prototypes are Stridalyzer-branded with exposed electronics, but the final product will be much closer to the concept renders.


WG: How much will it cost?
SS: The retail cost will be somewhere between $120 and $140, but there are substantial discounts available to our early backers on Kickstarter.

WG: So where can I buy one?
SS: Our Kickstarter campaign went live today, December 8th. We’re looking for at least $25k to get to the 500 pair production volume required by our manufacturing partners. Of course, we hope to raise more for our stretch goals.


The Kickstarter backers will be the first to receive Stridalyzer pairs, in April of next year. Around that time, we’ll also open up 2nd-round pre-orders through our website.

You heard it folks. You can check out Stridalyzer at the ReTiSense page or just head on over to the Kickstarter page to be the first to receive a pair when they launch. Also, be sure to like Stridalyzer on Facebook and follow @ReTiSenseInc on Twitter.

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