Concussion Prevention: The Promising Role of Neuro-Visual Training
Concussion prevention strategies can decrease the risk of sports-related concussion. Among these strategies, athletes should physically train their bodies for contact. Strength and speed training are beneficial, but training the brain may be more important. Hence, neuro-visual training may decrease concussion risk.
The powerful benefits of training neck strength for concussion prevention were discussed in a previous blog post. However, neck bracing for decreasing head movement can be dependent on anticipation of contact. One study showed that both greater neck strength and anticipatory neck muscle activation can reduce the magnitude of head movement upon contact.1
While neck strength training can be effective at improving neck strength, it does not address the anticipation of the brain to quickly activate neck muscles before a hit. So, let’s discuss neuro-visual training.
Neck Bracing for Contact is Dependent on the Neuro-Visual System
Neck muscle activation specific to bracing one’s head for contact is dependent on three factors: peripheral vision, brain processing, and reaction time.
First, peripheral vision is important for players to recognize moving objects around them, like other players, while maintaining focus on specific keys. The wider the peripheral vision, the more information the brain receives to understand one’s environment and anticipate the future.
Second, the brain must process or integrate this visual information with other senses. This may be hearing footsteps and other bodies, listening to communication from teammates, and feeling pressure or contact with an opponent. Brain processing gives players on-field body awareness in relation to others moving around and in front of them. Then, they can anticipate potential hits. The brain’s processing speed enhances the speed of anticipation and is prerequisite to its motor response.
The third factor is reaction time. Reaction time is technically the entire process but considered here as the speed of the brain’s motor output to cause neck muscle contraction.
In total, the brain receives and integrates peripheral vision with other senses for anticipation and fast reaction time to activate the motor response necessary for impact bracing. Neuro-visual training may enhance this process to prevent sports-related concussions.
Neuro-Visual Assessments May Predict Head Impact Severity in Athletes
Studies show support for enhancing the visual and sensory systems in decreasing head impact severity among athletes. One study evaluated 38 collegiate football players on a battery of nine visual and sensory tests from clarity to reaction time.2
They found significant associations between multiple tasks and head impacts. The lower performers experienced a greater average head acceleration and higher frequencies of head acceleration at more moderate and severe magnitudes.2
The most predictive tasks of higher head impacts were target capture and perception span (tests of peripheral vision), near-far quickness (testing speed of eye movement and awareness from different depths), and Go/No Go task (testing response inhibition or speed of the brain to choose one target while ignoring another).2
If better visual and sensory performance can reduce the number and severity of head impacts, concussions may also decrease. Neuro-visual training can improve these functional assessments.
Faster Brain Processing and Reaction Time Can Decrease Head Acceleration
Studies also show that anticipation of hits can decrease head accelerations in real life scenarios.
Youth hockey players who saw a hit coming and anticipated it with better body position showed reduced rotational head acceleration for moderate impacts but not lower or higher collisions.3 High school male rugby players who were told to clench their teeth when making tackles during a drill—simulating anticipation—had earlier initiation of muscle activity and decreased head accelerations compared with those who were not instructed to clench.4
Similarly, high school soccer players instructed to clench their teeth when performing headers had faster onset of muscle activity and decreased head accelerations compared with the players not told to clench.5 Another study found that high school football players who saw and anticipated impacts in one recorded game had lower head accelerations.6
These small studies show hope that improving one’s ability to anticipate hits, possibly via visual training, can decrease head impact incidence and severity.
Neuro-Visual Training Decreases Concussion Rates at Division I University
The only current research on neuro-visual training is from Dr. Joseph F. Clark, PhD from the University of Cincinnati (UC). I have been grateful to learn hands-on from Dr. Clark through the Carrick Institute’s Neuro-Visual Therapy course in 2020.7
In his 2015 article, he showed that neuro-visual training decreased concussion rates in football players each of the four years (2010-2013) it was implemented compared to the previous four seasons (2006-2009).8
In the years before vision training, there were an average of 9.2 concussions per 100 players each season. After initiating training, only 1.4 concussions per 100 players each season occurred. The players individual performance on a Dynavision D2 board, measuring peripheral visual reaction time, significantly improved.8
The training was performed 6 days per week at 30-40 minutes per day for the two and a half weeks of training camp. Then, a maintenance phase of one day per week for 5-10 minutes occurred during the season. The intense training period started basic but increased complexity quickly once the players learned the drills.
For training, they used a Dynavision D2, which is a large board with multiple small buttons that light up—basically, a large, vertical whack-a-mole board. This works on peripheral vision, saccadic (fast) eye movements, and hand-eye coordination. Each player had position-specific training along with dual-task components like calling numbers or words that flashed in the center of the board.
They used Tachistoscope training on a PowerPoint program that flashed pictures of previous UC games. Each picture had a set of numbers/letters in which the players needed to identify along with answering a question about the photo itself.
They also used pinhole and strobe glasses to play catch with a variety of balls, sticks, and other objects. Pinhole glasses decrease visual input while strobe glasses alternately turn on or off vision to make the task more difficult.
Dr. Clark has continued to adapt and update the neuro-visual training at the University of Cincinnati with continual decrease in concussion incidence.
Three Pillars of Neuro-Visual Training
According to Dr. Clark,7 there are three pillars to neuro-visual training: oculomotor performance, eye discipline, and processing ability.
- Oculomotor Performance: dynamic movement of the eyes to improve speed, precision, and endurance while tracking an object or quickly shifting gaze.
- Eye Discipline: gaze stability or being able to hold one’s eyes on a target while still recognizing the surroundings.
- Processing Ability: efficacy of the brain’s ability to control the eyes’ movements and to process visual information and integrate with other senses.
These pillars can help anyone form a neuro-visual training program for athletes that is creative, fun, and effective for all individuals with low-tech and inexpensive pieces of equipment.7,9
Training should be performed 3-5 times per week for 4-8 weeks at the beginning of the season. Each training session should consist of 3-5 exercises that involve each of the pillars taking about 10-20 minutes for the day. Then, it should be performed 1-2 times per week during the season. Every day involves new exercises that rotate and advance in complexity, always maintaining the pillars.
Before beginning neuro-visual training, all players should be assessed for visual and oculomotor deficiencies by a qualified physician. An optometrist or neuro-optometrist are best for checking vision. A neuro-optometrist, chiropractic neurologist, or physical therapist are better options for eye movement testing. Any deficiencies may require glasses/contacts and individualized eye exercises for correction.
Neuro-Visual Training Exercises for Oculomotor Performance
To train oculomotor performance, exercises with dynamic eye movement are necessary like smooth pursuits and saccades. Smooth pursuits involve tracking an object moving through space, whereas saccades are fast eye movements from one spot to another.
Training smooth pursuits can involve playing catch with many types of objects: colored balls, wiffle balls, PVC pipe with assorted colors, or more advanced equipment like tri-pronged sticks. A ball can be bounced to work on tracking in lower visual fields, whereas sticks can be tossed from different angles for others. If using a reaction ball that bounces unpredictably, the eye tracking is more complex.
Saccades can be trained with paper letter charts that are placed on the wall. These charts contain 100 letters in a 10×10 format and are placed about 10 feet apart on a wall at eye level. The individual stands about 10 feet away bisecting the two charts and reads the first column of each chart by alternately switching their gaze from left to right all the way down the column. It can become more complex if the letters form words that the individual must identify.
These eye movements require both eyes to move together in the same direction, whereas other tasks need the eyes to move differently from one another. These movements occur when an object is moving in different depths: convergence when the object is coming towards the person’s face and divergence when the object is moving away.
The accuracy of convergence pursuits is necessary for tracking a ball to catch, whereas the speed of convergence/divergence saccades is important for scanning a playing field to gather information from the environment.
Rather than having the above letter charts side by side on the wall, the individual can stand in front of one chart while holding a smaller-sized letter chart in front of one’s face. Reading down the column alternates between the near and far charts to work on near-far quickness.
Similarly, a bead string (piece of rope that has different colored beads attached) can train near-far quickness by quickly transferring fixation from the farthest bead to the closest bead and back out. The bead string can also be used for convergence and divergence tracking, but this is best accomplished with pitch and catch type exercises.
Neuro-Visual Training Adaptations for Processing Ability
Processing ability is trained by making the above exercises more complex. Pinhole glasses or strobe glasses worn to remove vision in space or time forces the brain to fill in the gaps for successful completion of the exercise.
The athlete can combine the visual or eye-hand task with a lower body task. For instance, the athlete must move one’s feet in and out of taped sections on the ground that are either identified by color or number that another teammate or coach calls out. This dual mental and body task can be highly stimulating to produce positive changes in the brain’s processing ability.
If memory is a goal, while a player is doing an eye-hand exercise, another player can be calling out formations, plays, or random words/objects that must be memorized and tested after the completion of the exercise. This improves the communication of athletes on the field for processing changing play calls and assignments.
To train peripheral vision and processing ability, Uno cards can be flashed on both sides of the individual in which the order of colors must be called aloud and memorized or the individual must turn to see, call out, and memorize the numbers for each card. Creativity can increase enjoyment for improving the brain’s processing speed during neuro-visual training.
Neuro-Visual Training Exercises for Eye Discipline
Lastly, eye discipline is necessary for maintaining one’s eyes on a target during sports, driving, and working on a computer. It is also important in social interactions where eye contact is vital for effective communication and building trusting relationships.
While it is not as fun to train, the easiest way to exercise eye discipline is using the Troxler Effect. Using your favorite search engine, you can type in ‘Troxler effect,’ and you will find a grayish background with purple dots surrounding a black cross. If you stare at the black cross, you will see a green dot moving around the purple until all the purple dots disappear.
This is an optical illusion in which eye discipline on a central target led to fading of peripheral dots although they are still present. The better one maintains focus on the cross, the faster the purple dots will fade and remain gone.
Next, Tachistoscope—as Dr. Clark uses—with a PowerPoint that flashes images containing a small alphanumeric symbol overlying the image. The individual only has a short amount of time to absorb as much visual information as possible and identify the letters and numbers that overlie. This is very challenging because it combines eye discipline with peripheral processing.
Lastly, eye discipline can be trained by staring at an object that will change (like a clock moving from 7:58 to 7:59) while others are utilizing visual and auditory distractions in the periphery. When it changes, the athlete must complete a specific action while identifying certain distractions.
Conclusion
A neuro-visual training program can help athletes improve their peripheral vision, brain processing, and reaction time. An efficient neuro-visual system not only helps with performance but also protects players from injury in an ever-changing environment.
The better awareness players have of their surroundings, the more they can anticipate contact and react faster to protect themselves. This may decrease head impact severity and accelerations.
Neuro-visual training is an effective tool in preventing sports-related concussion.
References
- Eckner JT, Oh YK, Joshi MS, Richardson JK, Ashton-Miller JA. Effect of neck muscle strength and anticipatory cervical muscle activation on the kinematic response of the head to impulsive loads. Am J Sports Med. 2014;42(3):566-576.
- Harpham JA, Mihalik JP, Littleton AC, Frank BS, Guskiewicz KM. The effect of visual and sensory performance on head impact biomechanics in college football players. Ann Biomed Eng. 2014;42(1):1-10.
- Mihalik JP, Blackburn JT, Greenwald RM, Cantu RC, Marshall SW, Guskiewicz KM. Collision type and player anticipation affect head impact severity among youth ice hockey players. Pediatrics. 2010;125(6):e1394–401.
- Hasegawa K, Takeda T, Nakajima K, Ozawa T, Ishigami K, Narimatsu K, et al. Does clenching reduce indirect head acceleration during rugby contact? Dent Traumatol. 2014;30(4):259–64.
- Narimatsu K, Takeda T, Nakajima K, Konno M, Ozawa T, Ishigami K. Effect of clenching with a mouthguard on head acceleration during heading of a soccer ball. Gen Dent. 2015;63(6):41–6.
- Schmidt JD, Guskiewicz KM, Mihalik JP, Blackburn JT, Siegmund GP, Marshall SW. Head impact magnitude in American high school football. Pediatrics. 2016;138(2):e20154231.
- Clark JF. Course 511: Neuro-Visual Therapy. Oral Presentation via: Carrick Institute for Graduate Studies; December, 2020; Cincinnati, OH.
- Clark JF, Graman P, Ellis JK, Mangine RE, Rauch JT, Bixenmann B, Hasselfeld KA, Divine JG, Colosimo AJ, Myer GD. An exploratory study of the potential effects of vision training on concussion incidence in football. Optom Vis Perform. 2015;3:116-125.
- Clark JF, Colosimo A, Ellis JK, Mangine R, Bixenmann B, Hasselfeld K, Graman P, Elgendy H, Myer G, Divine J. Vision training methods for sports concussion mitigation and management. J Vis Exp. 2015;(99): e52648.
