How One Startup Is Using Motion Tracking to Improve Your Tennis Swing

We're nearing the end of tennis season—the ATP World Tour final is in November—and pro players will head back to the practice courts before the new season starts in January. But fine tuning one's game is a luxury that most amateur players cannot afford.

Tennis is, by and large, an exclusionary sport, limited by its accessibility. You need a decent racket. You need courts near your residency; you can't rally against your garage door forever. You need playtime on those courts. And unless they're public courts, they usually aren't cheap.

But equally importantly, you need someone to teach you, especially if you want to do more than hit and giggle. It is nearly impossible to become proficient, even on a casual level, without a professional instructor of some type; there are just too many technical matters of form and stance. And an individualized class is out of the price range for nearly everyone.

But sports tech company Zepp is becoming an equalizer. Zepp's tennis sensor, which is mountable to the bottom of a racquet, tracks play via hard data. But more importantly, it converts that data into informed advice, an essential component to education.

"Depending on the skill level of the athlete, they might have a lot of one-on- one time with a coach, and for others, Zepp might be their primary coaching source," says Bill Lucarelli, the VP of Global Sales and Marketing. "Regardless of their access to professional coaching, we provide actionable data to help them improve their swing."

Zepp's first sensor-based, 3D-imaging technology was designed for a golf swing, which, if you think about, is easier to track than other sports motions. A ideal golf swing is predictable in its arc and orientation. The ball is teed at a fixed position, and the player keeps his two feet planted on the ground. From golf, Zepp expanded its sensor technology into baseball swings. Again, a bat swing's arc is fairly rounded and predictable, and the player stands in a fixed position. One does, however, have to deal with a moving, dynamic ball, which can be pitched high, low, and with varied spin.

From baseball, Zepp moved into tracking and imaging tennis serves. This required a bit more intricacy—an ideal tennis serve does not move in a natural arc, but instead has an odd up, back, and outward motion that forms a looping path.

It's the slight variations on that motion that determine whether a tennis player hits a flat serve, a slice serve, or a kicker. And if you, the player, have weak points—perhaps an inconsistent toss or contact point with the ball—the mobile phone app, which interprets the sensor's data, will direct you to tutorial videos (the latest addition to the technology's fourth generation). You can also view your serve, captured in 3D, from every conceivable direction and angle.

The sensor technology, while creating 3D images for serves, does not create 3D images for groundstrokes. Lucarelli concedes the difficulty of implementation. After all, how can an app accurately advise two players, one of whom uses an Eastern grip:

And another, who uses a Western grip:

The technology does, however, track groundstroke data, such as the type of spin on the ball, how quickly the ball is moving off the racquet, and where on the racquet head the ball is making contact. Players can even track their consistency over multiple sessions.

Professional tennis player Milos Raonic, who was ranked the #4 in the world in 2015, endorses Zepp, and he uses the sensor during his practices.

"The times I find it helps me the most are either when I have taken a break or when I'm thinking I am doing things well, but the ball is not coming off the racket as I would hope," says Raonic. "Sometimes, my coach will be there with my phone in his hand, and we'll look through it after a few shots so we can adjust throughout practice."

"Normally when I play points, I actually use it [the technology] on ground strokes," says Raonic. Then I can see how I'm getting around and if I'm having a good enough ratio [of forehands to backhands]. When I'm playing my best I'll be hitting 2:1 or 3:1 forehands throughout points."

Most casual players would not worry about running around to their forehand; they would be preoccupied with hitting well from both wings (and ought to be). But Raonic, a professional player, who already hits well from both wings, is using Zepp's tech as a way to optimize his game, and play to his known strengths. In this way, the technology is quite flexible. Novices might want to see how hard they are hitting the ball. Intermediates might be more concerned with their spin on groundstrokes. And even experts like Raonic can mine useful information.