A Connected Sleeve Finds That Pitchers Need To Alter Their Warm-Ups

Motus’s Sleeve is taking aim at baseball’s UCL surgery epidemic, and its first set of findings are counterintuitive.

A Connected Sleeve Finds That Pitchers Need To Alter Their Warm-Ups
[Photo: via Motus]

The rapid rise of ulnar collateral ligament reconstructions, better known as Tommy John surgery, is hurting baseball. More than 20 major league pitchers have had surgery already in 2014, and this particular problem has begun appearing in players as young as 13 years old. It could become a serious legal liability for leagues and coaches if someone doesn’t figure out how to curb the problem soon.


To date, understanding the stress a pitcher places on his or her ulnar collateral ligament (UCL) has been a function of rudimentary measures like height, weight, and velocity. But in September, pitchers from nine Fall Instructional League baseball teams wore a sensor-connected armband called the Motus Sleeve to establish a baseline understanding of the load placed on a player’s most valuable ligament.

Screen of prototype application, consumer version to be released in early 2015

“Basically,” explains Ben Hansen, vice president and CTO of Motus, “the Sleeve provides trends of performance and workloads on that UCL and that allows coaches to make better decision with their pitchers and managing their arms, as well as the players themselves.”

The newly released findings are insightful, albeit counterintuitive. The startling conclusion: Traditional training and warm-up methods might be doing more harm than good.

“The numbers show that UCL stress between long toss (warm-up throws of over 180 feet), dry work (throwing motion sans baseball), bullpens, and live throws are not as proportional as we may have thought,” reveals Hansen, “with each throw placing cumulative stress on the UCL. The sleeve now allows us to measure exactly how much each throw adds to this. You could never do this with your eyes, and now we can tell pitchers when they are throwing too much and with too much stress.”

Motus found that a “long toss” taxes a player’s UCL more than live, in-game throws–-a startling statistic considering the practice’s prevalence during pre-game drills.

The sleeve itself contains reactive accelerometers and gyroscopes, and identifies different pitching motions on board. When a pitch is thrown, the data recorded is stored in the sleeve and then downloaded, either in real time or whenever an appropriate device is within Bluetooth range.


Motus’s physics engine then takes the raw data from the sleeve’s sensors, including arm speed and angle, and converts it into smart data. Measures such as arm torque and UCL stress become clear, allowing pitchers and coaches to better understand where there’s a potential for injury.

Historically, the eye test and self-report have been the only reliable ways to determine player fatigue. Reflective markers and high-speed video technology have been used to develop 3-D models of players’ bodies, but that takes the kind of time and effort that limits the tech’s availability to maybe once or twice a year.

But Motus has found that pitchers sometimes drop their arm slot–from overhand toward sidearm–by as much as 19% during games. This change happens slowly, however. Over the first few innings, only about a 3% drop in arm angle occurs on average, meaning that over the course of the next few innings there can be a much sharper decline. Identifying when the dropoff occurs, then, is crucial not only to protecting a one-run lead, but also the pitcher’s ligament.

“When an athlete is stressed by too many throws, or too many high-torque throws,” Hansen explains, “we can kind of see when they’re at the end of these ranges where they break down. We also look at if their elbow is dropping or if their arm slot is changing dramatically, if it’s a good release point anymore.”

Where the sleeve truly excels is in its ability to map delivery or, the motion responsible for the wear and tear on a player’s arm. “The hardware can detect any kind of throw,” says Hansen, “from a Little Leaguer playing catch, to Justin Verlander’s fastball, to Mitch Stetter’s sidearm or underarm delivery. What we are really good at is then taking that data and getting mechanics off of it and computing things like torque at the elbow at different velocities.”

Motus is aiming to use the sleeve to track throw mechanics during live competition as well, in order to pinpoint when a player is peaking. These single game numbers can then be compared to season averages to isolate an individual players’ tendencies.


“We’ve been doing assessments, and specifically pitching assessments at our biomechanics lab for about four years now,” says Joe Nolan, cofounder and CEO at Motus. “But the goal has always been to take these analytics that are specifically focused on optimizing performance and reducing the risk of injury, taking that lab experience and bringing it to the players on the field.”

A consumer version of the Sleeve and accompanying app are in development, but for now Motus is working to improve their own data. Instead of simply tracking individual mechanics as a whole, the next version of the Sleeve will provide pitch-specific breakdowns so that coaches can compare stress across a pitcher’s entire repertoire.

“Some feedback we’ve got from coaches already,” says Hansen, “has been the ability to see if [a pitcher] has the same mechanics–the same arm speed and arm slot–for a fastball versus your curve ball. Coaches really preach that same delivery, that repeatable delivery. We’re giving them a space to analyze that.”

With the data already collected at the Fall Instructional League, Motus hopes to help stem the rash of Tommy John surgeries. The 3-D motion capture lab–which maps players’ deliveries and mechanics on-site once the data is uploaded from the Sleeve–is portable and the company is confident that it will be used in spring training for as many as 20 teams when pitchers and catchers report in February.

And ultimately the Sleeve could be used in other sports as well.

“We’ve been collecting data and building the physics engines specifically for general mobility and stability, golf swing analysis, baseball batting, tennis, la crosse,” says Nolan. “We’re prepared to launch on a much wider basis. Right now, our focus and immediate goal is to perfect pitching and get to the market and prove it out. But right on the heels there’s definitely multiple sports and multiple opportunities for the company.”

About the author

Matt Hartigan writes about sports technology for Co.Labs. He graduated from the University of Southern California in 2006 where he studied English, Psychology, Fine Arts and spectatorship