Review: Stryd

The problem with running is that there’s no way to constantly adjust your effort for best results. You often go out too slow or too fast, then feel awful—or worse, get hurt and leave the sport for good. A long list of heart rate monitors and GPS trackers have attempted to quantify performance, but none of them telegraph one simple metric tailored to a runner’s own body.

In the crowded field of wearable plastic gizmos, a new device promises to give you an objective number to guide your runs. Stryd, from startup Athlete Architect, borrows the idea of “power” from competitive cyclists (or maybe Nietzschean scholars), and applies it to running. Power is the kinetic energy you release with each step. To use the device, you clip on a sensor and view your power either on your smartphone or on the heart rate screen of many sports watches. (I like the way the Stryd folks have hacked the signals showing power so they show up as heart rate on sports watches instead of the metric they were designed for.) If you are using the smartphone display, a voice comes on every minute telling you the average power in watts. At the end of the run, an online page displays a tidy pie chart showing how much time was spent in the easy running zone, the medium aerobic zone, or the cookie-tossing anaerobic zone.

Before giving the device back, my last test with Stryd was a mountainous 5K trail race (average watts, 197.5!) in which I tried out the “impact” feature. It showed how hard I was hitting the ground, which was apparently pretty hard. I remember that early in the race I treaded lightly down the hills, but on the last steep decline, in the rush of chasing the runner ahead, I let out all the stops. Sure enough, the graph (above) showed that all my running in the last meters is fringed in the high-impact red. Not surprisingly, an old running injury flared up in my foot the next day. Using Stryd in this way seems like the perfect recipe for improvement—by increasing my power over longer periods of time while dialing back impact with attention to form, I could be running faster and with less wear-and-tear. In other words: More watts, less pounds.

Bob Parks (@bobparks), a get-gadget correspondent, ran the 2014 Boston Marathon in 2:54:53.

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