Neck Strength & Concussion Prevention
In the United States when it comes to high school sports an estimated, 1.6-3.8 million concussions occur each year and its estimated 10% of all contact sport athletes sustain concussions yearly. 1.
Each sport comes with it’s own risk to injury. Sports that involve physical contact and/or collisions and heading have higher rates of concussion. In fact many studies have shown high school girls soccer having higher rates of concussion than high school boys football. 2, 3
With high school sports being an integral part of so many family's lives it's crucial that we do what we can to help prevent as many of these injuries as we can. Over the last two decades the research on concussion, causes of concussion, concussion treatment, and concussion recovery has drastically changed and improved.
With high school sports being an integral part of so many family's lives it's crucial that we do what we can to help prevent as many of these injuries as we can.
In 2021 a group of researchers set out to see what progress has been made when in comes to reducing the incidence of sports related concussion and neck injuries.
They did this by performing a Systematic Review which is looking at all the research in a specific category and then diving into that research, looking at the nuances and variabilities, then drawing a conclusion.
In this blog I'm going to dive into what they looked at, what they found, and why concussion prevention is key and attainable for athletes across all sports.
The objective of the researchers was to investigate the relationship between neck strength and sports related head and neck injuries and whether neck exercise programs can reduce the incidence of sports related neck and head injuries and concussions.
First some background.
Head and neck injuries are continually a growing cause for concern in sports and athletic endeavors. Over the years doctors have gotten a lot better at being able to diagnose when a concussion has occurred and help get the patient on the path to recovery.
The risk of sustaining a sport-related concussion or neck injury is greater in sports like hockey, football, soccer, lacrosse because they involve body contact, projectiles, additional equipment, all moving very quickly at high speeds.
While concussions and neck injuries in sports are overall rare they're also the third leading cause of severe injuries in NCAA sports. So they're not that rare.
So why do sports related concussions(SRC) occur?
They occur as a result of either linear or rotational acceleration of the brain which can be caused by either a direct impact to the head or from force being transmitted from the body to the head. Most commonly this is going to be your head-to-head hits which we've seen both the NCAA and NFL try and reduce, head to body hits, head to ground, or head to object; like a hockey or lacrosse stick.
Less commonly they occur due to force transmission, like a whiplash injury, think of a check in hockey where a player shoulder checks another but they're not hitting their head on the boards, ice, or the opponent. Rather it’s just a violent whiplash like injury that results in a level of rotational or linear acceleration that results in a concussion. While I'd love to dive more into the mechanisms and pathophysiology of concussion that would make for a lot longer post so you'll have to keep an eye for that post on a later date.
Now back to the study.
In this study the researchers state, "Targeted interventions that reduce the burden of disease in at-risk populations are the best way to ease global public health problems such as sports-related head and neck injuries, including SRC."
Basically saying that when there is a group that is more at risk than others, we need to find out why and focus on improving it with specific interventions. This is why we are talking about neck strength and concussion.
When it comes to concussion there are two groups that are typically seen as more at risk, these two groups typically have prolonged recovery and a higher incidence of concussion. These two groups are young athletes and females. Both groups commonly have lower neck strength compared to other populations studied. It's thought that increasing the strength of the neck may help to mitigate the risk of head injuries, neck injuries, and sports related concussion. Decreased neck strength or neck dysfunction may also predispose athletes with a history of sports related concussion to sustain further sports related concussions. That's why we are talking about neck strength.
To touch on this again the researchers objectives were to look at all the literature and:
(1) investigate the relationship between neck strength and sport-related head and neck injuries including SRC, and
(2) evaluate whether neck exercise programs can reduce the incidence of sport-related head and neck injuries and SRC.
The researchers looked at 5 research databases.
They made sure the studies were quality studies looking at study design, participant characteristics, intervention and control, results and author conclusions.
Overall the researchers found 540 studies, but of those studies only 6 ended up meeting the high standards to be included into the review.
Two observational studies looking at 6792 male and female high school and university athletes, examining the relationship between neck strength and sports related concussion.
Four experimental studies looking at 3953 individuals investigating the effect of neck exercises on the incidence of head and neck injuries and sports related concussions.
Let's start with looking at the first two studies.
In the study by Collins et. al they looked at 6662 student athletes playing in three sports; lacrosse, soccer, and basketball. Three sports commonly played by both male and females. In this study they found that the odds of an athlete sustaining a concussion decreased by 5% for every one pound increase in isometric neck strength, the strength to maintain the head in a position. Essentially if I push on your head with 45 pounds of force and it stays there it has isometric strength at the level of 45 pounds. If the strength of the neck is increased and I pushed against the head with 46 pounds of force, the ability to still maintain that position shows an improvement of 1 pound of isometric strength which for these researchers resulted in a 5% decrease in risk of sustaining a concussion.
They also found that the relationship of the size of the head to the neck was associated with sustaining a concussion and a decreased neck circumference, smaller neck, was associated with a higher risk of a concussion. Also to note the above characteristics were more commonly found in female athletes.
In this group it was found that out of 1000 athletic exposures there were 4.9 concussions for female athletes and for males there were 2.5 concussions for every 1000 athletic exposures.
The way they look at frequency and how often concussion occur is they look at athletic exposures, which is basically a fancy way to say a practice or a game. In this group it was found that out of 1000 athletic exposures there were 4.9 concussions for female athletes and for males there were 2.5 concussions for every 1000 athletic exposures. Overall the researchers found that neck strength was a significant predictor of concussion among high school basketball, soccer, and lacrosse athletes.
The other study they looked at was an observational study looking at 130 university - varsity athletes, in this study they looked at the deep flexor muscles of the neck and tested them using the Deep Neck Flexor Endurance Test (DNFET), a test where you have the individual lay on their back, tuck their chin and elevate their head one inch from the ground making sure that the SCM and platysma don't activate, then the time one is able to hold the neck in that position is recorded. If you noticed they were looking at endurance not isometric-strength. Which in my opinion is why they found that there was not an relationship between the endurance of the deep flexor muscles of the neck and sports related concussion. We'll touch on this a little bit later, but the difference between isometric strength and endurance is important.
So far two studies, one showed individuals with necks that were stronger isometrically had less concussions than those with weaker necks. The other study looked at endurance of the deep flexors of the neck and found no correlations between endurance and risk of concussion for the positive or the negative.
Those were the observational studies, now lets look at the studies regarding the…
Effectiveness of Neck Exercise Programs on Reducing the Incidence of Sport‐Related Head and/or Neck Injuries.
For this they looked at three studies, Two cluster RCTs involving a total of 3807 rugby players. One study looked at high school rugby players and the other looked at adult rugby players. In both studies the intervention was similar and included a full body warm-up with balance movements as well as some neck strengthening. The third study they looked at was a pre-post study test with no control, ad we'll go over that one last.
Lets first start with some context on how these studies came about. There is a Injury prevention program called FIFA 11+ , to quote it directly.
" The FIFA 11+ injury prevention program was developed in 2006 to address injuries in soccer, it was developed under the leadership of the FIFA Medical Assessment and Research Centre along with the Oslo Sports Trauma Research Center and the Santa Monica Orthopaedic and Sports Medicine Center. It's a program that includes a complete warm-up aimed at injury prevention in soccer players. It has 15 structured exercises, and they consist of core stabilization, eccentric thigh muscle training, proprioceptive training, dynamic stabilization, and plyometric exercises, all performed with proper postural alignment."
This program has shown to reduce injury rates in soccer players by 30-72%. However, rugby and soccer are quite different sports, in rugby up to 80% of injuries occur when players are contacting each other, this could be a scrum, a tackle, or some other event where two players are coming in contact with each other, otherwise known as contact events. Again in rugby that's when 80% of the injuries occur. In soccer however only 44% of injuries occur during contact events.
So the researchers set out to see if an injury prevention program that was specifically created for the rugby population would get better results in reducing injuries in the adult male population. The prevention program was created by looking at what areas of the body was injured most and then working with a group of experts from the fields of sports medicine researchers to physiotherapists and strength and conditioning specialists specializing in human movement, injury prevention, epidemiology and rehabilitation.
The prevention program they created included proprioceptive, mobility and strengthening exercises within a progressive structure targeting the leg, shoulder, head and neck. As it progressed from week to week the difficulty increased. This was done by progressing the load, altering the sets and repetitions, increasing or decreasing the intensity and adding different variations. The resistance and plyometric movements also progressed in similar ways.
Overall the program contained 7, 6 week progressions that occurred during the off-season and into the season.
The control was a dynamic warm-up, resistance exercises, and sprint drills.
One thing that I thought was very interesting to note was the authors emphasis that in the intervention arm there was a "consistent theme of quality of movement control and body alignment" and feedback was given to the players.
Ok so we have the time of the intervention; a 42 week program to reduce injuries that are most likely to occur in rugby.
We have the population: 81 rugby clubs consisting of adult men
We have the control: A dynamic warm-up, resistance exercises, and sprint drills
Injury definitions is something we don't have.
So lets go over that;
First, Overall injury incidence, which looks at how many injuries resulted in a time loss of greater than or equal to 8 days.
Next is Severe injury incidence, how many injuries resulted in a time loss of equal or greater than 28 days.
Then we have injury burden looking at the total number of days lost, targeted injuries injuries to a specific area like the knee, neck, head, that were limited to ligament injuries, tendon injuries, muscles injuries, and joint injuries.
Here's what they found.
First looking at all incidences of severe injuries, injuries of 28 days or more and injuries equal to or greater than 8 days. There was no difference between the two groups. Looking at incidence of severe injuries there was no statistical significant difference, and looking at total injury burden so total amount of days lost from injury, there was a difference, in fact the intervention showed about 1100 less days loss than the control, but it still wasn't enough to be seen as statistically significant.
So when it came to the days lost from injury it was unclear if the intervention made a difference.
However, when looking at targeted injuries, injuries to specific areas like the ankle, neck and head, wrist, etc, there was a reduced amount of injuries that occurred resulting in 8 or more days lost and there was a reduction in incidence of targeted injuries that resulted in 28 days or more of lost time. So overall researchers found, "A likely beneficial 40% reduction in both overall targeted injury incidence and severe targeted injury incidence for the intervention compared with control group."
We're not going to get into every specific injury group because we have a lot more to cover. However, lets check out what they found when looking at injury burden and incidence to the neck and head and in regards to concussion.
When it came to looking at the incidence of head and neck injuries in the control versus the intervention there were 35 injuries for the control and 12 for the intervention. So nearly a third of the injuries in the intervention program. When we look at concussion incidence it was the same, a third of the injuries in the intervention group.
Looking at injury burden among head and neck injuries, so total days lost due to injury to the head or neck. The control had 1164 days lost due to injury while the intervention had only 378. Looking at burden, days lost due to concussion, the control lost a total of 983 days while the intervention lost only 378 days.
Based on the differences seen between the control and intervention when it comes to incidence and burden there was a significant enough difference between the two groups that points to the intervention being very beneficial for reducing burden of injury and incidence of injury when it comes to neck, head, and concussions. In fact when comparing the control to the intervention there was a 70% reduction in both incidence and burden for neck and head injuries and there was a 60% reduction in both incidence and burden when it came to concussion.
The next study that we'll look at is nearly identical to the one we just discussed but this one was done looking at school age rugby players. It was set up similarly when it came to the intervention and the control. Now the previous study had very similiar hours of exposure meaning similar hours of match play and practice between the control and the intervention. That led to nearly a one-to-one where showing 30 injuries in the intervention and 90 injuries in the control came out to some pretty easy statistical analysis showing the benefit of the intervention.
However, in this study the control had about 2100 hours less than the intervention so we are going to be looking at percentages and burdens and not specific numbers of injuries.
Here's what they found; teams that completed the intervention program 3x a week or more had a 72% reduction in overall match injuries, 72% fewer contact related injuries, 50% fewer days lost to contact injuries, 81% less upper limb injuries, 70% fewer lower limb injuries, and the whole reason of this blog, there was 59% fewer concussions. Something to note is that this was with the group that participated in the intervention greater than 3x a week.
The authors of this study concluded that, there were notable beneficial effects for decreasing upper extremity injuries, lower extremity injuries, and concussion incidence in youth rugby players.
The last study the researchers looked at was a pre-experimental study that looked at 27 professional rugby players, it had no control and took these 27 players through a neck strengthening protocol and compared the rate of injury and days lost due to injury of the season before the neck strengthening protocol and then looked at rate of injury and days lost due to injury after the protocol. As the authors put it, "The primary aim of the retrospective analysis was to determine whether the 26-week specific neck strengthening intervention program consisting of two phases; a 13-week pre-season phase and a 13-week maintenance phase had decreased the number of cervical spine injuries, and the severity (defined in relation to the number of associated missed training or match days) of these injures."
This is a really great study when it comes to looking at the impact nuances make in research. We're going to talk about what they found in the study and those nuances.
Here's what they found.
There was no significant difference between seasons for number of players with a cervical spine injury.
There was no significant difference in total number of cervical spine injuries.
There was a significant reduction I number of cervical spine injuries in matches/games. The season before there were 11 and the season during the intervention there was only 2.
There was not a significant difference in number days lost from training or games.
The primary aim of this study was to determine if implementing an isometric neck strength protocol was effective in reducing the number of cervical spine injuries and their severity. They found that there was significant decrease in number of match related cervical spine injuries. The secondary goal was to see if there was significant increases of neck strength with this protocol and there wasn't.
So in this study you had significant reduction in in-match injuries, but the proposed reasoning behind this was supposed to be increased neck strength leading to this outcome and there was no statistically significant increase in neck strength in this study.
Time for the nuances in this study. First lets talk about the fact that while there was not an increase in strength there was a decrease in-match injuries.
When we strength train any muscles the muscle is going to undergo some neurological adaptations that allow it to work more efficiently, improved muscle co-activation, increased neural drive, improve proprioception, and a greater stability of the muscle, specifically when looking at a complicated groups of joints involving the neck and head. Now none of these were measured throughout the study, but those are things that typically happen to a muscle when we train it and could explain the benefit seen, so we can't really say that's what led to the decrease in in-match play injuries.
The second nuance is that this study looked at gaining neck strength in a group of professional rugby athletes. Most likely a group that has highly developed neck musculature and strength. One thing ton note about strength training is once you get past the beginning and intermediate level of strength training its harder to make those big strength gains, which might explain the lack of statistically significant strength gains in the study. Lastly, this study was done on a very small amount of individuals, nothing like the other studies that we looked at that took into account over 6600 student athletes and the other looking at over 3800 rugby players. When you have a smaller study like this one its hard to really parse through the data because a few small changes can skew the data one way or another. For instance in this study when looking at time lost due to injury it was greatly improved before and after the intervention. 100 days lost in the season before compared to 40 in the season during the intervention. However, when looking more in depth at the data the researchers concluded that the evidence was skewed so they didn't draw that concussion.
So we've looked at 5 studies, the first looked at isometric strength of the neck and found that an increase in 1 pound of strength led to a 5% decrease in concussion risk.
The second looked at endurance of the deep flexor muscles of the neck and found no relationship between increased endurance of the muscles and a decrease in concussion risk.
The next two looked at preventions programs in two groups, one adult rugby athletes and the one schoolboy aged rugby players. Those two studies found that incorporating injury prevention programs that incorporated proprioceptive training, mobility, and strengthening exercises targeting the leg, shoulder, head and neck, resulted in significant reduction in head and neck injuries and concussion.
Lastly, we looked at the adult professional rugby study, where 27 athletes went through a neck strengthening protocol , didn't;t see significant increases in strength but did see a decrease in in match injuries.
They concluded that, "The results of this systematic review provide evidence that higher neck strength may be associated with a lower risk of SRC, with clinically worthwhile evidence to support the inclusion of neck exercises into injury reduction programs for contact sport athletes."
That is what the researchers who did this systematic review looked at. They concluded that, "The results of this systematic review provide evidence that higher neck strength may be associated with a lower risk of SRC, with clinically worthwhile evidence to support the inclusion of neck exercises into injury reduction programs for contact sport athletes."
That most likely this is due to the increase in strength of the neck resulting in a stiffer and stronger neck that is better able to stabilize the head during a collision. However, the authors made sure to note that there is conflicting literature out there where the specific benefit or mechanism of action comes from.
Overall when reviewing this literature and looking at what works, isolated neck strengthening can be beneficial when it comes to strengthening the neck and reducing the risk of injury.
However, multifaceted exercise interventions focusing on neck and trunk neuromuscular control, proprioceptive training, reaction time and mobility, in a structured manner that works to increase the workload and build resilience of the neck muscles and proprioceptive control system seem to have the biggest impact and the most evidence for further exploration. 4
I also want to note that there has been some amazing research out of the University of Cincinnati, with Dr. Joseph Clark and the department of neurology and rehabilitation looking at improving visual processing, visual fields, and visual reaction times and the effect that has on injury and concussion rates, as well at hitting percentages in baseball. I am currently enrolled in Dr. Clark’s Neuro-Visual Therapy Class through the Carrick Institute and will continue to learn more about the interaction between the neck, head, eyes, and vestibular system to better benefit our patients.
Most likely an inclusive injury reduction program would also incorporate neurons-visual training on top of a multifaceted program.
As always I hope you enjoyed this blog and if you have any questions feel free to email me at drcoffman@optimizecolumbus.com.