Over the past several months I’ve written about various companies attempting to put out sensors that measure and analyze a player’s strokes. Zepp, on the other hand, has already come to market. In fact, it’s swing sensor also has applications for baseball and golf. How does the multi-sport player perform on a tennis court?
Well my first session with Zepp ($150) didn’t go as planned. The app was easy enough to download and set up on my iPhone (it’s also compatible with Android devices), and synching with the sensor via Bluetooth was no problem. Getting the mounting sleeve onto my handle took some patience, but it wasn’t too difficult. However, I forgot to calibrate the sensor before my hitting session. It’s a fairly simple procedure of lying the racquet flat on the court with a particular part of the sensor positioned in the upper left corner. Then you calibrate the sensor through the app.
Skipping this step, however, causes the sensor to have a faulty reference point for your strokes, and all the subsequent data to be skewed. I have close to a full Western forehand and the sensor calculated 58% of my shots from that side to be slices. That’s positively Pam Shriver-esque.
I discovered my error, and the next time out this wasn’t a problem. It took me several attempts to successfully calibrate the sensor—getting the phone right next to the frame seemed to do the trick—but it didn’t take more than a few minutes. All my stats appeared to be much more accurate.
What does Zepp tell you? In the play tracking mode there’s a breakdown of number of shots hit by stroke: Serve, forehand, backhand, and smash; like some other sensors it doesn’t calculate volleys. Each of those shots are also broken town in spin type: Topspin, slice, and flat. (So some of those flat or slice forehands will probably be volleys.) There’s also a measurement of where you’re contacting the ball on the string bed. This is helpful to see how often a player is hitting the ball in and around the sweet spot.
Each stroke is also measured for power and put on a line graph to analyze variances in shots over time. The maximum number is denoted, as is the average. I was really surprised, as was my opponent, that my backhand averaged more of a punch than my forehand. I’m not sure what the numbers actually measure—maybe swing speed or ball speed potential—but they can be easily tracked over time. Whatever it’s calculating you can use as a benchmark and see if you’re improving upon it from session to session.
In addition to play tracking, there’s a 3D serving feature. It’s basically a top-down, side-to-side rendering of a player’s serve. It relays racquet speed, potential ball speed, a spin measurement, backswing time, and impact time. It’s probably the sensor’s coolest and most valuable feature. However, it’s an entirely different mode from play tracking and you have to change the setting in the app for it to work. It seems to be designed to be used solely during serving practice, and it would be even better if, in the future, it could be integrated with the play tracking mode.
There were a couple of concessions I had to make to play with Zepp. The first was I could easily feel the attachment on the end of my grip. I tend to hold the very bottom of my handle, particularly on the serve, so there was no way around it. That said, once I got acclimated it really wasn’t that bothersome. I’m not sure how my hand would react to rubbing the sleeve over the course of a long match, but for a short training session there were no problems. I suppose those who use overgrips could put the sleeve directly on the manufacturer’s grip, and then wrap the overgrip over the sleeve. While there might still be a slight raise in the grip, it would probably be less prominent, and you wouldn’t feel the rubbery material.
Even better, there’s actually a new attachment that wasn’t available for my testing that appears much less intrusive. It attaches directly to the butt cap without creeping onto the grip at all. From the looks of it, there would be minimal to no contact with the sensor during play.
The second compromise, though, is noticeable no matter how the sensor is attached to the frame. The unit I used added 20 grams to the end of my racquet, which has a static weight of about 357 grams to begin with; I’m not looking for any more mass. Being on the very end of the handle, the sensor does not increase the swingweight, but it makes the frame significantly more head light. I could still tell it was my racquet, but it clearly played a little differently. It would be beneficial if this new attachment cut some of this additional weight, so the frame played more like itself.
As it stands now, the Zepp sensor and accompanying app appear to be worthwhile tools for practice analysis. Given the impact it makes on the handle, I wouldn’t recommend it for match play. But for feedback on how cleanly you’re hitting the ball and measuring power production, especially on the serve, it has some definite value.