There is an old story that during the Cold War “Space Race” between the U.S. and the Soviet Union, NASA spent a fortune to develop a ballpoint pen that allowed astronauts to write in zero gravity, while the Soviet cosmonauts saved all that by just using pencils. It isn’t exactly accurate—but the story serves as a reminder of the value of simplicity.

In this day and age of sensors that measure everything from the steadiness of your breathing to the difference in where and how frequently one lands on the left foot versus the right, we are supplied with metrics that fill data-storage facilities vast enough to put to shame the warehouse at the end of “Raiders of the Lost Ark.”

Some of these measurement devices are lab-grade or clinical state-of-the-art tools, while others are relatively blunt instruments that rely on algorithms to estimate what is happening under your hood while you run

Consumers of the latter category have filed a class-action lawsuit, claiming that certain wearable devices fail to accurately measure heart rate, and that there is an extremely weak correlation between the user’s actual heart rate as measured by an electrocardiogram (ECG), and the wearable.

Were consumers really misled, or should they have known better? Can a small pod that mounts on your belt, chest, shoe or hat tell that much about your body? Shouldn’t runners seeking to improve their form and performance or to prevent injury be using sophisticated measurement instruments along with the watchful eye and guidance of trained coaches?

Or are these just inexpensive, dumbed-down pacifiers and “millennial devices” that provide perpetual rewards to encourage one to keep running? Does a consumer who purchased a low-cost activity tracker really have a legal gripe with the manufacturer? Heck, there is even a new wearable that measures your heart rate through ear-mounted biosensors and uses artificial intelligence to analyze the data and then coax you through your run via high-end earbuds and a soft, feminine voice. And how serious is an athlete who has to stare at a smartphone as they run in order to read the feedback?

When it comes down to it, all the devices do is help runners better listen to their bodies. They are amplifiers that help you hear what a trained athlete is attuned to hearing loudly and clearly.

Ultimately, once you learn to hear that voice, you can ignore the “metrics” and cease to track your activities. You train by feel and know when to push hard, when to rest, when a little ache is starting to become an injury and it is time for a massage or some cross-training.

Arturo Barrios, an Olympian who held the world record in the 10,000 meters, once gave a presentation at a running shoe store, where he went through the shop’s inventory, picking out item after item, saying to the audience, “You don’t need this heart-rate monitor, you don’t need this book, you don’t need these pricey shoes. … You just need to listen to your body!”

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