The majority of this article was written by Michael O’Connell, who is our first analyst in the Research and Development department of Driveline Baseball. He also collected all of the data and designed the study. This article was edited and approved by Kyle Boddy, President/Founder of Driveline Baseball.
This is the first of many research themed blog posts where we take a closer look at some of our in-house research. The objective is to share as much of the data as possible with you in order to encourage an earnest discussion amongst coaches on how to train healthier pitchers.
Update 8/25/2016: Since the publication of this article we have found a high intraclass correlation (ICC) of 0.99 for valgus/varus torque vs. stress(newton-meters) measurement of the Motus. Specifically between the American Sports Medicine Institute’s (ASMI) lab in Birmingham, AL and the MotusTHROW sensor. We can therefore suggest that the MotusTHROW sensor gives very close readings to the elbow torque values that ASMI publishes. You can read more about this finding here
In late 2015, the Bauerfeind EpiTrain Powerguard was released with several press releases accompanying the launch of the product. Part of the press release from their website states:
Working closely with Bauerfeind USA, [Dr. James Andrews] helped develop EpiTrain PowerGuard, the world’s first elbow support that helps prevent hyperextension for throwing athletes.
“The Bauerfeind EpiTrain PowerGuard brace was developed with my supervision to be a functional brace for a lot of different athletes,” Andrews said, noting that he envisions athletes in softball, football, javelin throwing and cheerleading also benefitting from the brace.
The EpiTrain PowerGuard features and individually adjustable Boa closure system that cushions the elbow to prevent hyperextension. The Bauerfeind Knit sleeve is extremely soft, comfortable and functional for wear during practice or games, and provides medically effective compression that aids proprioception and helps reduce pain and swelling.
“You can tighten [the Boa closure system dial above] the elbow and prevent extension, and the Bauerfeind Knit can help you control swelling that occurs around the elbow as well as prevention of hyperextension,” he said.
Driveline Baseball is extremely motivated to find and test out any equipment that can help with the rehabilitation of post-surgical pitching arms or to improve pitching mechanics through improved proprioception. There is mixed evidence regarding the effect of athletic sleeves around hinge joints and their effect on proprioception (¹, ², ³, ⁴). We could not find any published research data specific to the Bauerfeind EpiTrain Powerguard. As such, we decided to design a quick case study using new wearable technologies – we chose the mThrow Motus Sleeve to compare their “stress” metrics and other kinematics provided by their product.
The Bauerfeind Elbow Sleeve was created to reduce stress on the UCL by restricting the athlete’s ability to hyperextend their arm. It achieves this by tightening a string mechanism in the sleeve that sits in a V shape in the crook of the athlete’s elbow. When the sleeve is tightened, it reduces the amount of extension and/or hyperextension that an athlete can have in his arm. First, we tested the Bauerfeind elbow sleeve (anti-hyperextension) with the addition of the mThrow Motus sleeve. We sought to examine the stress measurement the mThrow sleeve provides to see if using the Bauerfeind sleeve simultaneously would reduce UCL stress or other kinematics without reducing velocity.
The tightening mechanism of the Bauerfeind elbow sleeve can be found on the side of the bicep and when tightened, the string pulls through the v-shape, as seen in the above picture.
For data collection we used the motusTHROW sensor, which recently replaced the mThrow.
When asked about the difference via Twitter, Motus Global emphasized that they had ceased supporting the mThrow. But the company said the layout of the printed circuit boards inside the devices had changed, along with the physics engine that produces the metrics from the sensor. A future update to the app will include fingertip velocity, which should correlate better to release speed across pitchers than the current arm speed metric.
We have always been excited to test out the sleeve developed by Motus Global because of what it could potentially offer; a sense of how stressful a workload is on a pitcher. From this, we would be able to make training decisions based off of those measurements.
In this experiment we were looking specifically at the ‘stress’ measure of the mThrow and seeing if it changed significantly whether the Bauerfeind sleeve was tightened or not. Motus defines their stress metric as “…a measure of the peak torque (Nm) placed on the UCL during the pitch near the time of maximum shoulder rotation…”
However, as Dr. James Buffi has brought up in a previous blog post, it’s very difficult to differentiate the stress that’s occurring on the elbow and the stress that is occurring on the UCL.
After recording the motion of the pitcher’s elbow, most institutions (including Motus and ASMI) use an inverse dynamic process to then calculate the total elbow load (or stress) in the form of a joint torque. Torque is simply force that causes rotation. Calculating this total load is fairly straight forward, as Sir Isaac Newton told us that force equals mass times acceleration. Sparing a few details, this means that the total elbow load is equal to the mass of the forearm and hand multiplied by its rotational acceleration. Now we have come to the gaping hole in this process… how do we calculate the specific load on the UCL from the total elbow load?
Due to the size of both sleeves, the motusTHROW and sensor was placed on the athlete’s arm first with the Bauerfeind sleeve on top, as pictured below.
Each of the five athletes wore both sleeves for a flat ground bullpen of 20 pitches. The first 10 pitches were thrown with without any tightening of the Bauerfeind sleeve. while the sleeve was tightened for the last 10 pitches. We did not measure the exact amount that the sleeve restricted motion. The intention was for the sleeve to restrict the last 5-10 degrees of motion an athlete had when fully extending their arm. Making full extension 170-175 degrees.
During testing, the top part of the Bauerfeind sleeve would be pulled down closer to the elbow during the throw, right around the time that elbow extension turns into a release point. We never had an athlete throw and have the string noticeably loosen, instead the top strap on the bicep would not stay in place. Readjustment of the sleeve, loosening of the tightening mechanism happened consistently every three to four throws. A possibility for why this occurred could have been that the Bauerfeind sleeve was on top of the Motus sleeve instead of the athlete’s skin, but similar problematic results were replicated in non-measured trials with the elbow guard in direct contact with a pitcher’s skin.
Our best theory on why stress increased when the sleeve was tightened is that when athletes were throwing, and nearing full elbow extension, more force was required to fight against the resistance that the Bauerfeind sleeve created in order to reach full extension. Instead of stopping the arm from reaching full extension, the player potentially would have to produce more force to reach full extension at release. This caused the sleeve to be pulled down and higher stress readings to appear on the Motus.
The data that we collected showed that four of the five athletes had increased stress on their arm during their 10 throws with the sleeve tightened.
We exposed all of the raw data in this case study; find it here if you are interested in seeing it and running your own analyses.
The ‘stress’ level on our athletes tested ranged anywhere from 20 -70 Nm (Newton metre, measure of torque). This seems to be quite a high range for athletes in similar age and skill level – especially when you consider that the range of the velocity of the five pitchers was large (maximum of 11 MPH difference).
In the end, while we are unsure of how accurate the mThrow’s stress measurement is, the data does not support a reduction of UCL stress while using the Bauerfeind EpiTrain Powerguard as measured by the Motus Global sensor package. Subjectively all five of the athletes who threw and wore the sleeve described the experience as something uncomfortable or feeling as though they couldn’t throw hard. The athlete’s physical comfort must obviously be taken into account prior to creating a program and using a new training tool.
¹: NO CHANGE IN UNINJURED ATHLETES: The effect of knee brace and knee sleeve on the proprioception of the knee in young non-professional healthy sportsmen (Knee, Bottoni et al 2013 – link)
²: SOME DEGREE OF PROTECTION TO LIGAMENTS: Impact biomechanics of lateral knee bracing. The anterior cruciate ligament. (AJSM, Paulos et al 1991 – link)
³: POTENTIAL INCREASE IN INJURY RISK AND CRAMPING: Prophylactic knee bracing in college football (AJSM, Rovere et al 1987 – link)
⁴: NO QUANTITATIVE DIFFERENCE: The effects of compression garments on intermittent exercise performance and recovery on consecutive days. (Int J Sports Physiol Perform, Duffield et al 2008 – link)