Disclaimer: Some information & data has been purposely left out due to the proprietary nature of this training method. We as a staff feel comfortable sharing this information as the majority of what is explained here is publicly available knowledge. We just pieced ideas together.
Our first attempt at having a hitter use ear plugs while hitting stemmed from the idea that deaf individuals have enhanced visual performance. (Hauthal et al., 2013 & Buckley et al., 2010) Later we discovered that the central nervous system (CNS) can reweight sensory input (Than, 2014 & Maheu et al., 2017) and that disturbing auditory cues increases the reliance on visual cues for postural control. (Maheu et al., 2017) Which we theorize that because more reliance is placed on visual cues with ear plugs in, there is less input to process causing visual perception and input from the vestibular system to be more accurate. We had already seen the benefits of using monocular vision training via eye patches, so constraining hearing to improve vision didn’t seem like too far of a stretch.
The vestibulo-ocular reflex (see gif below) uses information from the vestibular labyrinth of the inner ear to generate eye movements that stabilize gaze during head movements. Without the VOR, when walking down the street, it is impossible to read signs or even recognize faces. (Broussard et al 2010) Essentially this reflex stabilizes our gaze while were moving or in relation to hitting, the head turn that comes with tracking a pitch. Sound can negatively effect postural stability (Park, Lee, Lockhart, & Kim, 2011) and while there was no significant changes to early connection or connection at impact, observationally (we currently lack a device to quantify motion) hitters were more balanced upon finishing their swings and not falling over the plate as they had been in previous attempts to max out their bat speeds.
First and foremost the hitter has to understand intent. We also want it pointed out that the majority of ear plug rounds come off the machine. We as hitting coaches can at times get so caught up in chasing metrics that we forget the swing still has to be functional. If the hitter has no understanding of what a max level effort swing feels like, then ear plugs will have zero effect in our experience. The initial reports we received from hitters were that the baseball looked slower, it looked bigger, and all contact felt soft. Trying earplugs in myself I began to understand what they meant. It was almost as if because there was not auditory cue for contact with the ball so my brain didn’t know how to feel the sensation of contact. There were several swings that I took the ear plugs out and inspected the bat because I feared I had broken it. Contact felt like I was striking a roll of toilet paper.
Below is a small case study of a Division II hitter we worked with from the same sessions over the course of one week. Interestingly enough his attack angle changed as did his point of contact. Because his bat speed jumped his point of contact shifted to more out in front which could have caused the increase in attack angle.
Hearing Rounds (Less data points due to more swing & misses)
AA avg- 4.56
BS avg- 68.24mph Peak BS- 75.8mph
Deaf Rounds
AA avg- 8.05
BS avg- 70.25mph Peak BS- 82.8mph
HitTrax Point of Impact (December 15th Deaf Rounds, December 17th Hearing Rounds)
Over the course of the offseason in which he trained with us (5 weeks in total) this was how his swing speeds evolved over the course of that time. Again all swings are off a high velo machine and the machine is constantly moved to new locations.
While trying to understand why ear plugs were having this effect on almost every hitter we applied this too, we came across an interesting article. Auditory white noise reduces postural sway. (Ross & Balasubramaniam, 2015) So our next question was could we improve hitting posture or bat speed by simply having hitters listen to white noise? We read pink & white noise is commonly used in motor learning therapy for Parkinson’s patients. So we began building out Hostile Hitting Environments using auditory constraints. Below you can clearly see from our December hitting class that deaf swings performed the best. Initially swing speeds go down after putting ear plugs in, possibly due to learning how to perform with lack of auditory cues. Hitters learn to use the auditory cue of the pitching machine and taking that away forces all cues to run through vision. Which we believe is one of the draw backs of a pitching machine, there’s an auditory cue on every ball that’s not available on a live pitch.
On the pitching side we’ve experimented a little with it during pull downs and it has been promising, but we’re not far enough along to have much available other than speculation on the pitching side. One theory we’ve developed is could this help with pitching command since the CNS is re-weighting sensory input and could we make proprioceptive feel in the hand more sensitive to input. A discussion we will have in an upcoming post.
This summer we were able to perform some small scale field tests and while the results were very promising, it is still too early to tell what the implications are of using ear plugs, white noise, or music in game. See some of my twitter posts below for results from our small scale summer tests.
References (Click on the title to go to the article)
Visual movement perception in deaf and hearing individuals
Action video game players and deaf observers have larger Goldmann visual fields
Temporary Vision Loss Can Boost Hearing
Sensory reweighting after loss of auditory cues in healthy adults
Motor Learning in the Vestibulo-Ocular Reflex
Effects of Sound on Postural Stability during Quiet Standing
Auditory white noise reduces postural fluctuations even in the absence of vision
Baseball Thought Experiments 