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03
09
2020
motus sleeve

The MotusThrow Sleeve: Measuring What Matters

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Word that Boston Red Sox pitcher, Chris Sale, is using a motusTHROW sleeve this spring training has sparked a few articles. One of these articles mentions a quote from New York Yankees pitcher, Adam Ottavino, one of the more data-driven pitchers in baseball.

Ottavino had this to say about his reasoning for not wearing Motus sensors:

“I think if you’re going down the Motus rabbit hole, you’re probably looking to modify something in your arm action to stay healthier, and for me, I have no real interest in that because I’m only good because of the weird way I throw. I’ll take the risk of getting hurt to produce a higher level of success at this point.”

The primary use of the motusTHROW is not to change mechanics. For the sake of clarity, we’d like to briefly explain what its primary use is.

What Matters Most

When they first open up the motusTHROW app, many ask where they can find the real-time metrics. These days many of us are used to the instant gratification of throwing a pitch and getting immediate feedback.

This feature does exist and can be accessed by enabling Advanced Features from the app settings screen, but the feature is hidden for a reason: it’s not the app’s most useful function.

The MotusTHROW sleeve’s greatest value is in monitoring workload to help optimize a pitcher’s performance and to reduce the risk of injury.

For each ball thrown, motusTHROW provides data on arm slot, arm speed, max shoulder rotation, and peak valgus torque (stress). Because the app captures these metrics, it’s easy to assume that the motusTHROW is intended to be used to change mechanics.

This is a misconstrual because each of these metrics is specific to the individual player and cannot be used to compare different players or to determine good versus bad.

It’s also important to note that players throw from all different arm slots, and sometimes these differences are what make them successful.

For example, a Little League player can have more arm speed than an MLB pitcher (due to length of arm and mass of arm), and there has never been a strong correlation between torque measures and injuries.

Larger-sized players who throw hard tend to put more stress on their arm, but this brings us to the main reason to use motusTHROW: to track fatigue. Fatigue is the number one predictor of injuries, and of course, can’t be good for performance.

Measuring Workload with Acute:Chronic Workload

How does motusTHROW monitor fatigue? Through a concept called Acute:Chronic Workload Ratio.

AC Ratio was developed by Dr. Tim Gabbett, who used GPS monitors to measure total body workload in rugby players.

At Motus, we applied the same concept to the arm with our sensor that measures stress on the elbow. The sensor measures the stress of every pitch. The stress (peak valgus torque, in Newton-meters) represents the amount of torque placed on the Ulnar Collateral Ligament (UCL).

This peak torque then feeds into a pitcher’s workload calculations.

The workload calculations include Daily, Acute, Chronic, and Acute:Chronic Workload measures. Daily Workload is the total workload of all throws in a day. Acute Workload is the weighted average of the daily workloads from the past nine days.

Throws made today, for example, are weighted more heavily than throws made nine days ago. A Chronic Workload is the total workload from the last four weeks, or twenty-eight days. Lastly, the Acute:Chronic Ratio is the Acute Workload divided by the Chronic Workload. Together, these workloads provide key indicators of readiness and fatigue.

With Spring Training here, pitchers are building up chronic workloads, and it’s important that they do so at a manageable pace. To build up their chronic workload, a pitcher adds more daily workloads to their throwing regimen. But the question becomes how much to work to add?

Research from Dr. Sameer Mehta has found that an Acute:Chronic Ratio above 1.3 increased injury risk by over 1,500 percent!

At 1.3, a pitcher has increased their workload by 30% compared to what they’re conditioned to handle. For a pitcher to handle the rigors of the baseball season, they need to build up their chronic workload at a pace that stays under the 1.3 AC Ratio.

Measuring AC Ratio cannot be done by just counting pitches. In terms of stress, every throw counts and not all throws are equal. This is why the motusTHROW brings so much value to pitchers, both while they’re getting ready for the season and while they maintain their level of arm fitness or conditioning during the season.

Sure, there is value in looking at arm slot, arm speed, shoulder rotation, and torque data, but workload monitoring has proven to be what the MotusThrow sleeve does best. We provide objective data to help athletes and coaches make more educated decisions in regards to throwing, which will ultimately help pitchers perform their best.

By Bryan Goelz

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