On a day that is too damp and buggy to be typically Arizona, Los Angeles Dodgers pitching prospect Scott Barlow is doing an activity that isn't typical at all: He's throwing in his underwear. 

He's also wearing Dodger blue cleats and his ball cap, and three of his teammates are in similar get-ups. All are dotted with a couple dozen reflective markers, stuck to their bare chests and legs and the top of their heads, as is the case with any biomechanical pitching analysis. But normally, those take place indoors, in a lab. 

On this early October afternoon, the four hurlers are outside, in a cage at Camelback Ranch in Glendale, Ariz., utilizing the services of Motus Global's mobile biomechanics lab. And in addition to the markers, they're all sporting Motus' latest invention: the Pitcher Sleeve. In an era where ulnar collateral ligament injuries in pitchers, and the subsequent need for Tommy John surgery, have become all too common, the sleeve is viewed by many as potentially revolutionary. 

During baseball's instructional leagues in Florida and Arizona this fall, 36 pitchers from nine teams collected 15,000 pitches worth of data in a trial run with the sleeve. Some, like Barlow, have already had Tommy John surgery; he had his in 2012. Others are just tech-savvy kids who were willing to give the sleeve a try. Still more were just doing what they were told. The 21-year-old Barlow, for his part, thought it was "kinda cool." 

And he's right. 

The sleeve, which is visually similar to standard compression sleeves already worn by many pitchers, is fitted with a sensor that rests near the elbow and contains accelerometers and gyroscopes similar to those found in video game controllers and smartphones. (The gizmo that makes a cell phone screen switch from vertical to horizontal when it's turned sideways is an accelerometer.)  

The sleeve collects data on elbow height, arm slot angle, shoulder and forearm rotation, arm speed and release point, which can help pitching coaches accurately asses a pitchers' mechanics, and the decline thereof, over time. Most importantly, the sleeve is designed to assess fatigue, in the form of decreasing arm speed, and can calculate a pitcher's workload over a set period of time in the form of the force being absorbed by the UCL.

"The rotational forces, or torque, exerted on the elbow is the only measurement linked to stress on the Tommy John ligament," says Dr. Glenn Fleisig, who runs the research wing of American Sports Medicine Institute, Dr. James Andrews' famed research institute in Birmingham. ASMI partners with Motus, and Fleisig is on Motus' board. 

"You need to know both how fast the arm is accelerating and how fast it's rotating," he says. "Motus uses the exact equation necessary to measure torque on the elbow, and it's very exciting to be able to get the specific biomechanical measurement we need." 

sleeve_closeup
(Via Motus)

Here's a quick physics refresher. We all remember Isaac Newton and his apple, and the famous equation he derived: Force = Mass x Acceleration. When a pitcher begins using the Motus sleeve, he enters his height and weight into the app. A person's forearm is 1.6 percent of his bodyweight, his hand another .66 percent. Take Barlow. He weighs 210 pounds, so his hand and forearm weigh approximately 4.75 pounds, combined. The weight of the baseball -- five ounces -- is also factored in prior to release, and added together, that provides mass. The sleeve measures arm acceleration, and force is then calculated.

But the sleeve goes further. Newton also formulated that Torque = Moment of Intertia x Angular Acceleration, and to calculate torque, the gyroscopes in the sleeve's sensor also measures rotational forces on the elbow. Combined, these measures allow the sleeve to monitor stresses imparted directly to the UCL. 

Initially, while impressed with the sleeve's potential, teams found the data a bit clunky and its battery life a bit short. There are also some practical issues: Barlow said that during games, when he would sweat more than he did in an average bullpen or long-toss session, the sleeve would slide down. 

Said one coach. "They need to work the bugs out." 

Motus CEO Joe Nolan was listening. "It has to be comfortable, and if people see the data and can't grasp it right away, there's no use for it," he says. "So we spent a lot of time on improving the overall user experience." 

Motus unveiled the latest version of the sleeve and its accompanying software in a fifth-floor suite at the Manchester Grand Hyatt in San Diego at last week's Winter Meetings.

When spring training opens in February, pitchers -- mainly prospects -- will be wearing slightly longer sleeves made of snugger, more breathable material fitted with a smaller, more accurate chip with longer battery life. Previously, the chip could record data for 32 throws; now, that number is up to 450. Data will be received in an updated cellphone app, built by a designer who helped developed the Nike Fuel Band app, that is more comprehensive and intuitive than its predecessor and has a 90-foot Bluetooth radius.

Torque per pitch is displayed in the app, in Newton-meters divided by 1000 to make the number more manageable. Workload is calculated by multiplying the torque per pitch times the pitch count per week. 

Graphs are color-coded for easy readability and there is a gas gauge-like icon which literally shows how much a pitcher has left in the tank. The app sends text messages when a pitcher is nearing his max workload and at a greater risk for injury. 

"This information is valuable because it allows you to make better decisions on a day-to-day basis," says Motus VP of Technology Ben Hanson. "If the app tells you pitcher A is at risk for injury today because his workload is high, you can then limit his long toss or have him throw a shorter bullpen or he can do his PFPs tomorrow. You can find ways to limit the workload just by being aware."

However, some athletes just don't want to know, and many big-leaguers fall into that camp. Most pitching prospects are willing to try anything to make it to the Majors, and they're young; they grew up with iPhones in their hands and are comfortable with the technology. But pitchers who have already made it -- and the pitching coaches who oversee them -- have been historically reluctant to embrace technology that points out their flaws. 

"Baseball moves at a glacial pace, and wearable devices, which are already widely used in sports like football, rugby and soccer, are just starting to leak into our industry," says one coach. "In the big leagues, pitchers who figure out how to adapt to the stress can endure and make money and the ones who can't, can't. But nobody wants to be told what they can't do, so not everyone will want to wear a sleeve." 

Typically, though, an athlete who has been hurt is less opposed to making changes. Nick Conte, Dodgers minor league medical and rehab coordinator, also sees use for the sleeves in the rehab setting. Pitchers recovering from Tommy John surgery do exercises and activities in rehab that progressively challenge the UCL. "We go from one exercise to the next and we assume a certain amount of stress on the UCL, but we haven't had any proof as to exactly how much we were stressing the UCL," Conte says.

With the sleeve, though, doctors, trainers, therapists and strength and pitching coaches involved in the rehab process should be able to see exactly how much stress a specific exercise puts on the UCL, and can progress an athlete accordingly. And when the pitcher resumes throwing, rather than basing his throwing effort on a percentage of his normal miles-per-hour, it will be based on Newton-meters of force on the UCL. 

"That's where this could really redefine the way we rehab these injuries," Conte says. "It would make our protocols much less subjective and much more objective." 

In the past, the only effective measure against UCL injuries has been pitch counts to limit fatigue. But concrete proof that a pitcher is getting tired could drastically change the way coaches at all levels manage pitcher workloads. And while the sleeve cannot pinpoint specifically what is wrong with a pitcher's mechanics that causes the torque on his elbow to increase, it can provide immediate feedback when a pitcher makes an adjustment. Furthermore, the sleeves do not require a laboratory setting to collect data and can be used immediately in a game situation, unlike other forms of biomechanical analysis.

Sleeve_3
Motus' sleeve will be available to the general public next spring. (Via Motus)

However, because only a full biomechanical analysis can explain why certain results are occurring, Motus offers big-league teams an analysis in conjunction with the use of its sleeves. 

Still, the sleeve alone, and the information it provides on workload, could be a valuable tool in the prevention of injury. And soon, the sleeve will be available to more than just the pros. Motus hopes to have the sleeves available to the masses in the spring, at a cost of about $150 per sleeve. (For comparison, a full biomechanical work-up in a lab can cost up to $1000).

"Ultimately, I want biomechanics to be at the point where you collect in-game data without any markers and get full-body biomechanics," Fleisig says. "It would be amazing to be able to get in-game data that says, so-and-so's elbow is dropping, he's still not rotating his trunk enough and he's losing velocity and control because of it. The Motus sleeve is revolutionary because it's the first portable step to get us to that point." 

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Lindsay Berra is a reporter for MLB.com and a contributor to Sports on Earth.