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Neck Strength and Concussion Risk

 

Neck muscles are historically one of the most unsexy muscles to train and develop in athletes. When we look at the main reasons that people take up training we find things like:

  1. Cosmetic (look better with less clothes)
  2. Enhanced performance in a specific sport
  3. Weight loss

The problem is that having a thick, strong neck is not seen as terribly sexy (especially for women) . A strong neck isn’t going to make professional scouts look at you closer on the football field, and certainly no one is asking you how much weight you can pull in neck extension.

In spite of these obstacles, there’s been a growing movement in sports science to pay more attention to the neck as a possible way to mitigate an athlete’s risk of concussion. Some circles are even hailing a strong neck as the only way to truly protect athletes from concussive head injuries. But what does the science say?

History of Neck Training

The buzz about strengthening the cervical spine came as a reaction to a 2014 study published in the Journal of Primary Prevention by Collins et al. [Source] The paper was on an observational study performed on over 6,000 high school athletes whose training staff assessed the strength of their necks and observed their risk of concussive injury over the course of a year.

The study found that people with smaller and weaker necks were at a higher risk of concussion during the school year. In fact, the defining sentence from the abstract shows why people were so excited about this study:

“For every one pound increase in neck strength, odds of concussion decreased by 5%” – Collins et al, 2014

The paper received a lot of buzz, and the idea of neck strengthening even became featured in a USA Today article featuring a colleague and renowned concussion expert Dr. Tad Seifert. [Source]

Truthfully, this is not a new concept to strength and conditioning coaches involved with boxing, mixed martial arts, and football. Neck exercises have been a staple in boxing for decades because stronger necks allowed fighters to take a harder punch. Just take a look at how Floyd Mayweather trains his neck.

A number of NFL teams became early adopters of weekly neck exercises to prepare their athletes for the inevitable high speed collisions that occur in football regularly. [Source]

How Does A Strong Neck Protect Your Brain?

A lot of the ideas about neck size and strength is related to the basic physics of acceleration.

Contrary to popular belief, a concussion is not simply a matter of taking a large blow to the head. Classically a concussion is seen through the lens of a coup/countercoup injury mechanism. An object strikes the skull, the skull hits the brain, and the brain hits the opposite side of the skull.

Classically brain injury is thought in terms of the brain colliding against the skull.

Classically brain injury is thought in terms of the brain colliding against the skull.

Much of the damage done to the brain and nervous system actually have a lot to do with acceleration and deceleration. This rapid acceleration and deceleration inside the head will cause a shearing force into the central structures of the brain including the midbrain, brain stem, and diencephalon.

The sudden deceleration in a concussion leads to tearing of the axons in the central portion of the brain.

The sudden deceleration in a concussion leads to tearing of the axons in the central portion of the brain.

That’s where a thicker and stronger neck may make a difference. Bigger and stronger neck muscles are capable of absorbing more force from an impact. That means that a strong and robust muscular system can take on that energy as opposed to letting the force go into the spinal ligaments and neural structures. If the amount of force of an impact is equal, then a bigger and stronger neck will be harder to accelerate which means decreased movement of the brain, and decreased shear into the central brain structures.

 

Do Neck Strengthening Programs Help?

As of now, we know that bigger and stronger necks are correlated with a reduction in concussion and this seems to make good sense. It helps to explain why girls have a higher rate of concussion than boys when playing equivalent sports like soccer [Source].

So here are the million dollar question:

Will neck strengthening reduce the incidence of concussion?

In other words; does someone who is naturally bigger and more muscular have a higher resistance to concussion, or can we train the neck to be more resilient?

In regards to concussion, we don’t really know the answer to that yet. There hasn’t been a study that compared groups of people who train their necks and how it impacts concussion rates….at least not yet.

We can make some educated guesses based on what’s been published in the literature about neck exercise and head stability, and neck exercise and general injuries.

The studies that looked at training programs and head acceleration don’t appear to be optimistic. Mansell et al looked at college soccer players using an 8 week neck training program found that training did not reduce head acceleration from a soccer ball header. Nor did it affect displacement, or EMG activity even though strength levels went up.[Source] Lisman et al found a similar result in trained college men during a football tackle. Although the men showed increased strength, there was no detectable difference in acceleration, displacement, or EMG activity. [Source – Lisman Paper]

Schmidt et al found that increasing stiffness of the neck does reduce rotational acceleration of the head, but parodoxically found that those with stronger and larger necks did not protect from higher impacts. [Source]

Most of the critiques of that study are that it tested stabilization in an unreliable way within a laboratory setting. Could results of players in a real setting dispute the acceleration data?

The data is pretty limited there, but a study of professional rugby players found that neck injuries did go down from one season to the next after the team participated in a 26 week neck training program. [Source] The rugby team focused mainly on isometric exercise which may mean more for an athlete because it is the neck’s ability to produce stiffness and stop motion that will help reduce the acceleration injury.

Thoughts on Neck Strengthening Programs

Thanks in part to the Collins study, there has been a greater effort to meet the demands of people wanting a way to prevent concussion by doing neck exercises. The list of contraptions that have hit the market that say they can prevent concussion is sometimes staggering.

Before you buy a fancy contraption for neck strength, we have to remember that neck muscles are like any other muscles in the body. If you repeatedly make them work against resistance, they will get stronger and be able to generate stiffness.

Some strength and conditioning coaches have advocated the idea that basic strength training alone will generate enough neck contraction without specific neck exercise, but this was disputed in a study by Conley in 1997. [Source] The study found that heavy compound lifts alone came up far short in terms of strength and hypertrophy than a program that included a neck specific exercise.

A review of published studies on different neck exercise programs showed that all kinds of neck exercises targeting the neck could produce measurable strength gains. These include isometric exercise, banded resistance, neck specific machine exercise, and even exercises against a coach’s manual resistance. [Source]

Ultimately, your neck is more likely to put on mass if you use a program that involves a neck harness with free weights or a machine with the ability to increase the resisted load. However, these studies have shown that subjects can make sizable strength gains within 8-12 weeks time by doing banded isometrics or using manual resistance even without hypertrophy.

In the end, you don’t need fancy equipment to get a strong neck. Just just need to do the work.

If you want a great guide for a wide range of neck exercises with video explanations, you probably won’t find a better resource then this article on Bret Contreras’ blog:

 My Take

As it stands today, we don’t truly know if you can truly reduce your odds of concussion through neck exercises, or if you just need to be born with the genes to have a big/thick neck. The good news is that anyone can do basic neck exercises on a regular basis for minimum investment and no real downside.

If you are an athlete that is in a high level combat or contact sport, it’s likely that you are already engaging in some form of neck training. For these athletes, it’s important to get your neck strong, but the truth is that there is probably a point of diminishing returns. Why? Because no amount of neck strength is likely to protect you from having a concussion after a hit like this:

 

No amount of neck strength is likely to stop this type of concussion.

No amount of neck strength is likely to stop this type of concussion.

 

Perhaps the biggest beneficiaries of a neck training program isn’t for professional athletes. It’s most likely to benefit our youth athletes and female athletes! The concussion rates in youth or female athletics may be a product of having a smaller or weaker neck. Many of the collisions in these sports are often a result of incidental contact, and are not as severe as those in tackle football, yet concussions happen more frequently.

Here are some other observations that aren’t proven yet by research, but I believe will play a role as we start to understand more.

  1. Proprioception may play just as important a role in susceptibility to concussion as strength. Exercises and treatments that focus on joint position sense proprioceptive stimulation seem to be helpful in rehabbing patients with concussion symptoms.Just like balance and proprioceptive exercises can help athletes mitigate ankle and knee injuries, I think these types of exercises may help the neck become a little more resilient to sprain/strain injuries.
  2. Isometric exercise may be more important than concentric exercise. Since we are talking about stopping acceleration of the head and neck, we want the neck to develop stiffness in response to an applied force.While taking a neck movement through full range with hundreds of pounds may be cool to some (unlikely), by making your neck resist moving against an applied force has a more realistic application than doing heavy neck curls.
  3. Don’t play a sport with a sore neck. If you are going to train your neck, do most of the training in the off season and do maintenance exercise programs during the season.Starting a program of neck exercises can and make your neck sore. Sore necks are not great at turning and avoiding danger. Sore necks are also more likely to instigate a headache/pain process for a short term. You don’t want that short term period to happen when you’re playing in a game for real.

 

 

 

Rectus Capitis Posterior Minor in Headache Disorders

Neck muscles have been a source of suffering for patients for a long time. In recent years, one neck muscle in particular is getting a lot of attention in the world of head injury.

Meet the rectus capitis posterior minor (RCPMi)

Image Credit: Duke Univeristy Learning labhttps://web.duke.edu/anatomy/Lab01/Lab2_new2014.html

Yep. It’s that tiny little muscle deep in the middle of your neck. It connects from the top bone in your neck called the atlas, and it connects into the head via connective tissue called the myodural bridge. But more on that later.

All in all, the the RCPMi is not much bigger than the end of your pinky finger, but it’s capable of wreaking havoc on people with neck problems including concussion.

Headaches, Trauma and the Rectus Capitis Posterior Minor

The RCPMi has been considered a muscle of importance in chiropractic literature for a long time. It’s only been a recent phenomenon where more mainstream medical science has started to look at its role in headaches and trauma. Two such studies examined the RCPMi in 2016.

The first study was published in the American Journal of Neuroradiology. They saw that patients with atrophy in the RCPMi had more severe concussion symptoms and a worse prognosis. You can check out the abstract here:

Effect of the suboccipital musculature on symptom severity and recovery after mild traumatic brain injury

The second study was published in the presigious headache journal, Cephalgia. The authors found that patients with chronic headache tended to have more hypertrophy in the RCPMi than controls. You can check out that abstract here:

Correlation between chronic headaches and the rectus capitis posterior minor muscle

In case you weren’t paying attention, you should probably find those 2 outcomes to be a little strange.

On one hand, having smaller RCPMi had worse outcomes with concussion symptoms. On the other hand, having larger RCPMi was more likely to be associated with chronic headaches.

Granted we are dealing with 2 different conditions, but one of the biggest problems with chronic concussive symptoms is chronic headache. It would seem like there should be some overlap. What gives?

How Can That Small Muscle Cause So Many Problems?

There’s a few unique things about these muscles.

  1. The RCPMi does not connect into bone like most muscles do. It connects into a piece of tissue called the myodural bridge. That means it has a direct link into the outer covering of the brain which is known to be very sensitive to pain.
  2. The RCPMi is too small to provide much in the way of meaningful movement of the head and neck. Inside the belly of this small muscle are abnormally large amounts of prorioceptors called muscle spindles. Proprioceptors help provide feedback to the brain about joint position and movement.
  3. Changes in the RCPMi can deform the myodural bridge which changes movement in cerebral spinal fluid. Abnormal movement of this fluid is associated with headache.

So as you can see, even though the RCPMi is small it carries a large baggage of neurology with it.

What’s Happening in Headaches and Concussions?

This is where things get a little interesting, because we don’t really know how this muscle is causing problems. More evidence is showing that there is a correlation between this muscle and headaches, but we don’t really know anything about causation yet.

With that being said, this is mostly just speculation on my part, so here it goes.

In my office we are always striving to create symmetry in the structural positioning of the head and neck.

When the head and neck shift, it creates asymmetrical force production in the suboccipital muscles. Image Credit: Daniel O. Clark uppercervicalillustrations.com

When there is an injury like a trauma or whiplash, you create injury in some of these small muscles of the neck. When these muscles are injured, the brain loses some critical feedback mechanisms that helped to maintain proper positioning of the head and neck.

The injury also creates asymmetrical tension on the myodural bridge. This abnormal tension on the dura stimulates the sensitive pain receptors in this tissue leading to head and neck pain. There have even been cases where cutting this muscle can relieve a patient of chronic headache.

That same tension on the dura may also be creating abnormal flow of cerebral spinal fluid which may lead to chronic effects of brain physiology.