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Motus Sleeve debuts at fall instructional league

A partnership with nine teams allowed Motus Global to test sleeve and study in-game mechanics

Al Bello

Biomechanics technology firm Motus Global completed a pilot study of the Motus Sleeve in partnership with nine Major League Baseball teams during this year's fall instructional league games. Coaches and trainers from the teams -- the Astros, Braves, Dodgers, Indians, Mariners, Orioles, Pirates, Red Sox, and Yankees -- received real-time information to help optimize their pitchers' performance and to prevent injuries.

The sleeve, announced earlier this year, was used on a daily basis by coaches and players to track metrics such as arm slot, arm speed, and torque on the elbow. By wearing the sleeve during a game, coaches could quantify how their pitchers' mechanics changed as they fatigued. An example of the sleeve was on display in this recent interview, along with some of the calculated metrics. CEO Joe Nolan said the partnership was a useful learning experience for his company.

"It was very helpful for us to have access to the teams, to see how they think about injuries," Nolan said.

The metrics, outlined in the table below, weren't used solely for injury prevention. Nolan said most coaches who used the system on a daily basis were more interested in the performance optimization aspects of the sleeve. As an example, the sleeve showed whether certain pitchers were tipping their pitches, by slowing their arm when they threw changeups or using a different release point for their curveball.

Basic Metrics
Angular velocity of forearm
Linear velocity of wrist
Linear velocity of elbow
Peak elbow varus torque
Maximum shoulder rotation
Relative height of elbow
Arm slot at release
Relative distance to release point

On the injury prevention side, the system calculated each pitchers' workload as a function of the number of pitches they threw, amount of rest they had, torque on their arm, and efficiency over the previous seven days. By wearing the sleeve every time they threw, Chief Technology Officer Ben Hansen explained, pitchers could get a snapshot of what they did on game days and throughout the week.

"Even though every throw isn't max effort, every throw counts," Hansen said.

Hansen also described the alerts the system provided as players fatigued or their workloads went too high.

"We tried to compute things that are easy for the players and coaches to grasp," Hansen said.

Thanks to their partnership, Motus received data from all nine participating teams to help further develop their algorithms. Each pitcher also went through a full biomechanical analysis using motion-capture cameras. Hansen was excited about the initial findings his group was able to make with the data.

"From the first to the last inning, we saw arm slot drop by 19 percent," Hansen said. "After the first inning, the arm slot dropped by three percent, so it was a gradual decline as the pitcher fatigued."

In addition to the live metrics coaches received during game action, the system allows users to track throwing programs on their off-days. Hansen said that tracking long toss sessions and throwing off flat ground led to more interesting discoveries.

"So for long toss beyond 180 feet, we found 14.4 percent more elbow torque than what goes on during a game," Hansen said. "And then, for throwing on flat ground, wrist velocity was 51 percent of what it was during a game, and elbow torque was 30 percent."

The system consists of a detachable waterproof sensor, containing an accelerometer and a gyroscope, attached to a compression sleeve. A Bluetooth transmitter with a range of about 30 meters is included to relay data to the dugout on each throw; when the connection is lost, some memory is included to store throws until the connection is restored. The sensor's on-board firmware can detect a variety of throwing styles and techniques, from max effort fastballs to Little League lobs; from pitchers who throw straight over-the-top to submariners. Data from the sensor is stored on a cloud server and processed using Motus' physics engine to give players feedback on their throwing motion.

The company plans to make the sleeve available, along with customized analytical models based on the company's research, to MLB and collegiate teams in time for spring training. Motus Global also plans to release a standalone version around the same time for individuals to purchase. In the meantime, Motus Global is working on a white paper detailing the system's accuracy, which he hopes to have ready for the MLB Winter Meetings; Hansen said the company is also partnering with independent groups to get "third-party, unbiased studies" of the system published in the spring.

But Nolan was encouraged by the sleeve's largest-scale deployment to date, and was happy to call this partnership a success.

"The response from players was so great," Nolan said. "We spent a lot of time focused on the technology and the design, so that wasn't surprising, but it was interesting."

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Bryan Cole is a featured writer for Beyond the Box Score. He was in no way compensated by, nor does he endorse, any of the companies or products mentioned above. You can follow him on Twitter at @Doctor_Bryan.