The Cervical Spine

01What the measurements show

The Numbers on Neck Injury in Sport

Eight findings on the athletic cervical spine, from the common stinger to the rare cord event.

02Seven bones, one cord

The Cervical Spine Carries the Most Critical Hardware in the Most Mobile Segment

The cervical spine is seven vertebrae asked to do two jobs that fight each other. It has to move the head freely and protect what runs through it. The top two segments handle most of the rotation and the nod. The atlas at C1 carries the skull, the axis at C2 gives it a peg to turn on, and C3 through C7 stack into the lordotic curve that absorbs and distributes load.

Inside that column runs the spinal cord. Between each pair of vertebrae a nerve root exits to feed the shoulder, the arm and the hand, eight pairs of them in a seven bone column. The vertebral arteries thread up through the transverse foramina to supply the brainstem and the cerebellum. No other region packs this much critical hardware into so small and so mobile a space, which is exactly why the neck rewards both protection and precise training.

Neck motion never arrives in one plane

Cervical motion is not what a goniometer suggests it is. A review of the functional anatomy concluded that movement into a single plane is not the product of equal and summative movement among the cervical vertebrae Swartz 2005. Individual vertebrae can reverse direction while the head travels through one plane, and motion in one plane usually requires contributed motion in one or two others.

For an athlete that has a practical edge. A neck can produce a normal total range while one segment inside it is traveling the wrong way, so an end-range number tells you almost nothing about how the work is divided. The segment-by-segment reading is the one that matters, and The Spine as Athletic Axis carries the same argument for the column as a whole.

The upper neck is not exempt from athletic injury either. In 13 years of catastrophic football injury surveillance, nine athletes sustained an isolated injury at C1 or C2 Boden 2006. Seven more sustained a combined injury at C1 or C2 and a level below it. A subaxial finding does not rule out one above it.

The receptor field packed into these seven segments is among the densest concentrations of nervous system input anywhere in the body. The counts and the cervicocephalic kinesthesia literature belong to The Neck as a Sensory Organ, and this page carries what that field does under athletic load.

03The stinger down the arm

A Stinger Stays on One Side, and That Is How It Is Told From a Cord Injury

A stinger, also called a burner, is a transient injury to the brachial plexus or a cervical nerve root that sends a hot electric jolt and numbness shooting down one arm. The hallmark is that it stays on one side, separating it from a cord injury, which strikes more than one limb. That single distinction decides what happens in the next 60 seconds on a sideline.

Two mechanisms produce it, and the surveillance systems record them separately. The league database that tracks these injuries logs each one as a brachial plexus stretch or a brachial plexus compression Lamplot 2024. The stretch version is a forced lateral bend away from the arm with the shoulder driven down. The compression version pinches the C5 or C6 root as the head is driven toward the involved side.

The volume is high. Five National Football League seasons produced 691 in-game stingers and an average single-season risk of 3.74 percent Lamplot 2024. The rate ran higher in regular season games than in preseason games, 12.26 against 8.87 per 100,000 player-plays. Concomitant injuries were found in 7.09 percent.

What the symptoms actually cost

The arm symptoms follow a recorded pattern rather than an anecdotal one. Among 569 young rugby players, the most frequent symptom was numbness in one upper limb and the most severe was weakness of grasping, which carried a mean severity of six days Kawasaki 2015. Mean severity across all stingers was 2.9 days.

Most cost nothing. In that rugby cohort 79.3 percent of players lost no time at all, and in the NFL record 76.41 percent missed nothing. The tail is what matters. In the rugby study 5.8 percent needed more than 14 days, and an injury with more than three symptoms, motor weakness above all, predicted the longer course.

Recurrence is the finding that changes the plan

A second stinger is a different event from a first one. The reinjury rate inside a single rugby season was 37.3 percent, and a history of stingers in the previous season was the strongest risk factor for another one Kawasaki 2015. The neck that has produced a stinger is the neck most likely to produce the next, and a pattern of them signals a neck that is no longer tolerating its load.

Canal geometry enters at exactly that point. In a prospective study of college football players, initial stinger incidence was 7.7 percent and did not depend on the canal to vertebral body ratio at all Castro 1997. Players who experienced multiple stingers had significantly smaller ratios than players who experienced one, 0.75 against 0.87.

The authors proposed 0.70 as a more statistically defensible threshold for advising a collegiate athlete about recurrent stinger risk. That is what a recurrent stinger buys: a real neurological examination, objective strength testing, and a look at the canal the root is leaving through. Nerve tension testing along the arm belongs to Adverse Neural Tension.

04When both arms go

Bilateral Symptoms After a Hit Are a Cord Event Until Proven Otherwise

Transient quadriplegia is a temporary loss of motor or sensory function in both arms, both legs, or all four limbs after a load to the neck, and it is a medical emergency until proven otherwise. The deficit is bilateral, which is the signature of the cord rather than of a single root. That is the whole triage question on a sideline: one limb or more than one.

The syndrome was defined from 32 patients. Sensory changes included burning pain, numbness, tingling and loss of sensation, and motor changes ran from weakness to complete paralysis Torg 1986. Recovery was usually complete in 10 to 15 minutes, though in some it resolved gradually across 36 to 48 hours.

One detail from that series belongs in every locker room. Apart from burning paresthesia, neck pain was not present at the time of injury, and cervical motion came back full and painless. An athlete who feels normal 15 minutes later, with a comfortable neck, may still have had a cord event.

The rate is low and the surveillance is consistent. A survey of 503 schools playing NCAA football in the 1984 season found 1.3 per 10,000 athletes with a history suggestive of cervical cord neurapraxia Torg 1986. Catastrophic injury surveillance later logged 43 such episodes across 13 years, or 3.31 per year Boden 2006.

The mechanism is axial load, not the violence of the tackle

What produces these injuries is the position of the neck at contact. Analysis of registry cases and game film showed that the majority of cervical fractures and dislocations in football were caused by axial loading Torg 1985. The crown of the helmet strikes first, the lordosis is flattened, and the column takes the force straight down its own axis.

Cadaver work explains what happens next. Under an axial-load impact the cervical spine demonstrates a buckling effect, and both the impact location and the orientation of the head decide the degree and the level of the resulting injury Swartz 2005. A straight segmented column does not distribute compression. It folds.

That is why the technique that causes most catastrophic cases is coached out, not coached around. The registry authors named the same mechanism in diving, rugby, ice hockey and gymnastics, wherever the head is delivered first into a fixed object.

What happens in the next few minutes

The athlete with bilateral symptoms after a hit is immobilized, evaluated and imaged before anyone discusses return. Escalating to that level of response is correct dosing rather than caution. The Unified Model of Tone states the rule directly. When a distortion has descended past what any surface input can reach, the larger magnitude is the correct one, and delay becomes its own kind of harm.

The decision rules that determine who gets imaged, including the NEXUS criteria and the Canadian C-spine rule, belong to Cervical Trauma and the Systematic Read. The field sequence, spine boarding and equipment removal included, belongs to Emergency and Field Care. The cervical spine check is also step three of the sideline concussion assessment, which Concussion carries in full.

05Neck strength and the head

A Stronger, Pre-Braced Neck Changes What the Head Does After a Hit

Neck strength changes head kinematics, and that has been measured directly rather than assumed. Maximum isometric neck strength was recorded in every anatomical plane in 46 male and female contact sport athletes aged 8 to 30 Eckner 2014. A loading apparatus then applied impulsive forces to the head in flexion, extension, lateral flexion and axial rotation.

Two conditions were compared: a baseline state, and one where the athlete braced the neck for the coming load. Greater isometric strength and anticipatory activation were each independently associated with lower peak linear velocity and lower peak angular velocity of the head, across all planes of motion, at P less than .001. Effect sizes ran from r equals 0.417 to 0.657.

The bracing half of that result is the one a performance program can act on. Anticipation is not a tissue property. The athlete who sees the hit coming answers it with a different neck from the athlete who does not, and the difference shows up in the velocity the head reaches.

Whether that reaches concussion rates is where the studies split

The strength measure has been taken to the field twice with opposite results, and both belong on this page. Athletic trainers at 51 high schools across 25 states recorded preseason neck measurements on 6,704 athletes in soccer, basketball and lacrosse Collins 2014. Smaller neck circumference, a smaller neck to head circumference ratio and weaker overall neck strength were each associated with concussion.

After adjustment for gender and sport, overall neck strength stayed a significant predictor at p equals 0.004. Every one pound increase in neck strength went with a 5 percent decrease in the odds of concussion, an odds ratio of 0.95 with a 95 percent confidence interval of 0.92 to 0.98.

The professional result went the other way. Among 136 male professional rugby players, 40 sustained 51 concussions across the 2017 to 2018 season, and peak isometric flexion strength was not associated with concussion risk Liston 2023. Neck muscle endurance, age and playing position were not associated either.

Extension strength reached statistical significance in the wrong direction, an odds ratio of 1.01 that the authors judged too small to be clinically relevant. Concussed players had neck strength similar to players who were not concussed. The strongest predictor was previous concussion, and more than two in the previous 12 months carried an odds ratio of 9.51.

Why neck strength separated one population and not the other

Two populations, one measure, two answers. The Unified Model of Tone expects exactly that. There is no such thing as an input acting upon an empty body, and the effect of any event is determined by how it interacts with the organism's existing tone.

The high school sample spanned a wide range of neck strength and preparation, so a strength measure had room to separate athletes. Professional rugby players are selected for neck strength and collide with people who are also selected for it. A measure that discriminates in a spread population stops discriminating in a narrow one.

The sharper reading is this. Strength is a quantity, and the organization is the timing of its delivery. Both were measured in the laboratory study and both mattered independently, yet only the quantity has been carried into the field studies. Nothing here claims that neck training prevents concussion, and the consensus on concussion itself belongs to Concussion.

06The neck that reports

The Athlete's Neck Reports Where the Head Is, and Contact Sport Degrades That Report

The cervical spine is a primary organ of proprioception. The deep suboccipital muscles at the top of the column, rectus capitis and obliquus, are dense with muscle spindles that report where the head sits relative to the trunk. That signal feeds the vestibular and visual systems that hold gaze steady, and it sets the athlete's sense of where the body is before a movement starts.

Contact sport measurably degrades it. Twenty young elite rugby players, ten forwards and ten backs, were compared with ten young elite athletes from non-contact sports Pinsault 2010. The instrument was the cervicocephalic relocation test, which asks an athlete to return the head to neutral after full active rotation.

Both rugby groups showed higher absolute and higher variable error than the athletes who do not tackle. Forwards and backs did not differ from one another, and the errors were the same before and after a training session. The authors concluded that the alteration comes mainly from tackling rather than from the scrum. It is a season effect, not a fatigue effect.

The error the athlete cannot feel

The same test separates concussed adolescents from uninjured ones. Forty-six adolescents tested a mean of 11.3 days after concussion relocated the head to neutral with a mean error of 4.3 degrees against 2.9 degrees in 83 uninjured controls Smulligan 2025. The effect size was a Cohen d of 1.19.

The test discriminated well. Area under the curve was 0.81 on its own and 0.85 after adjustment for age, sex and concussion history, and a 3.5 degree cutpoint classified 80 percent of participants correctly. Twelve trials with the eyes closed, three in each direction, and a protractor.

What that number describes is the gap between where the athlete thinks the head is and where it actually is. Nothing about the gap is available to introspection, which is why it has to be measured. The model expects a sharper map to show up as faster reaction, steadier balance and more precise movement. Joint position sense as an instrument, and what an error in degrees means across other joints, belongs to Proprioception and Joint Position Sense.

Disrupted cervical afferents show up as dizziness and unsteady gaze when the head turns, which is why cervical and vestibular work sit together in the concussion recommendations. Gaze stability during head motion, and the sway measures that go with it, belong to The Vestibular System and Balance.

07Clearing the neck for contact

Return to Contact Is Decided by Findings, Not by the Calendar

A neck goes back to contact on findings. Full pain free range of motion, symmetric strength and a normal neurological examination come first, with the specific deficit resolved. After a stinger that means full deltoid, biceps and grip strength with a clean sensory examination. After any cord level event, imaging and specialist evaluation come before the conversation about play.

The formal criteria now come from a consensus process rather than from a single clinic. Spine surgeons from the Cervical Spine Research Society and National Football League team physicians ran a three round modified Delphi study on collision athletes after cervical spine injury Schroeder 2020.

Two thresholds reached strong agreement. Asymptomatic athletes without increased magnetic resonance imaging signal change and a spinal canal diameter greater than 10 mm may return, at 90.5 percent consensus. Athletes whose signal changes had resolved with a diameter greater than 13 mm may return, at 81.3 percent. A screening scan before participation for athletes with a history of cervical injury drew 78.9 percent support.

The surgical picture is narrower. There was strong consensus at 84.4 percent that asymptomatic athletes without increased signal changes may return after a one or two level anterior cervical fusion but not after a three level fusion. No consensus was reached for collision athletes after a two level fusion, and none for pseudarthrosis. Where a consensus panel stops, the decision belongs to the treating surgeon and the team.

The canal ratio does not decide

The measurement most often quoted at athletes cannot carry the decision. A canal to vertebral body ratio at or below 0.80 reached 93 percent sensitivity for transient cord episodes and a positive predictive value of 0.2 percent Torg 1996. The authors also found that developmental narrowing in a stable spine did not appear to predispose an athlete to permanent catastrophic injury.

Their conclusion was that such narrowing should not by itself preclude participation in contact sport. The catastrophic injury record points the same way and keeps the caution. Of 43 athletes with cervical cord neurapraxia across 13 years, 16 returned to football and none suffered a permanent quadriplegic event Boden 2006.

One case in that series cuts the other way and belongs in the record. An athlete with a Brown-Sequard-like syndrome and permanent neurological symptoms had reported a cervical cord neurapraxia episode before the study period. The decision is individual, and it is made on canal diameter, symptom status and imaging signal rather than on a ratio.

Training the neck as a performance asset

Beyond clearance sits the part most programs skip, which is training the neck as a performance asset. That work is a performance decision as much as a safety one. Direct cervical strengthening and deep neck flexor work build the strength and the bracing capacity that the laboratory study found independently associated with lower head velocity after a load Eckner 2014.

The neck that is strong, mobile, and well mapped is the neck that both survives the hit and moves with command. Reading that neck is shared work. A team physician, an athletic trainer, a spine surgeon and a chiropractic neurologist each hold a different instrument, and the criteria-based framework the whole decision runs inside belongs to Return to Play.

08What we corrected

Five Claims About the Neck Corrected or Removed

This page previously reported stingers in up to 65 percent of college football players over a career. That figure could not be traced to a source and it is gone. The measured numbers replace it: 33.9 percent career prevalence in young rugby players, a 3.74 percent single-season risk in the NFL, and a 7.7 percent initial incidence across one college football season.

The page required adequate canal space before any contact, treating a canal to vertebral body ratio below 0.80 as the gate. It called a low ratio with a prior episode of transient quadriplegia a genuine contraindication to collision sport. That is corrected. The ratio has a positive predictive value of 0.2 percent, and its authors wrote that developmental narrowing in a stable spine should not preclude participation Torg 1996.

It also stated that direct cervical strengthening lowers stinger and concussion forces. No study supports that as a claim about injury rates. What has been measured is the head's kinematic response to a laboratory load, and the two field studies of neck strength and concussion disagree with each other. Both are reported above, in full.

A fourth claim held that repeated traction quietly degrades the C5 and C6 sensory pathways. No source was attached to it. The recurrence evidence replaces it and says something more useful. A stinger in the previous season is the strongest risk factor for the next one, and athletes with multiple stingers carry smaller canal ratios than athletes with one.

Fifth, the page said an athlete can rotate the head nearly 90 degrees to each side and closed by claiming that care manages the nociceptive signaling that otherwise locks a segment down. Neither statement carried a source. Both are removed.

The page also carried a quotation attributed to Dr. Jason Dulberg that was not drawn from anything he said or wrote. It has been removed. Every claim here is either sourced to the literature or named explicitly as the model's.

09The model's claim

The Neck Earns Its Claim on Density and Access, Which Is Proximity, Not Rank

Two layers run through this page and they stay separate. The established science is the stinger epidemiology, the injury registry and the rule change that followed it, and the canal geometry statistics. It is also the head kinematics under impulsive load and the relocation errors in rugby players and concussed adolescents. Every one of those stands on its investigators' work and is cited above.

The Unified Model of Tone adds a reading, and the neck is where its access claim lands hardest. Seven small segments carry the cord, eight pairs of nerve roots, two arteries feeding the brainstem, and a receptor field dense enough that a 4.3 degree repositioning error counts as a clinical finding.

That is proximity, not rank. Access describes where the input sits in the anatomy, and it settles nothing about which professional an athlete needs on a given day. The model does not rank these interventions, and it never counsels anyone to decline care they need. This page sent the athlete with two numb arms to an ambulance for exactly that reason.

The prediction this page makes

The neck strength disagreement is where the model earns its keep. Strength is a quantity. The organization is the timing of its delivery. One laboratory study measured both and found each independently associated with the head's response Eckner 2014, and only the quantity has been carried into the field.

The model predicts that adding the timing measure separates athletes the strength measure could not. In professional rugby players, peak isometric strength told concussed players apart from unconcussed players not at all Liston 2023. Cervical muscle onset latency before a predictable load has never been recorded in that population.

The design is one collision squad across one season, and every instrument already exists. Record head repositioning error in degrees on the cervicocephalic relocation test. Record cervical muscle activation onset latency in milliseconds before a signaled load. Record peak head angular velocity per unit of applied force in the same rig. Record time to return to baseline heart rate variability, read as RMSSD, after a standardized collision session.

This is a claim about how the athletic neck is organized rather than a claim about what treatment does. The four readouts are already collectable in one squad, in one season, with equipment a team either owns or can borrow. If head repositioning error, cervical muscle onset latency, peak head angular velocity and time to return to baseline RMSSD are shown to move together within athlete across a season, the unification claim is confirmed.

10The tone reading

The Neck Read as One Regulated Segment

Three signatures of tone carry this page, and each already has a number recorded at the neck itself.

The other foundations of tone show up in the same seven segments. Constraint is the canal itself, where a ratio at or below 0.80 caught 93 percent of the athletes who had a transient cord episode and predicted almost none of them. Time-course is the 10 to 15 minutes most of those episodes take to clear, against the 36 to 48 hours some of them take instead. Coupling is why no cervical motion arrives in one plane alone, so a segment can reverse direction while the head appears to turn normally. Gain is how strongly the deep neck muscles answer a load, which separates a braced head from a whipped one. Set-point is the neutral head position an athlete relocates to with the eyes closed, and after a concussion that target sat 4.3 degrees away instead of 2.9. Oscillation is the stride and breath rhythm the head has to stay level inside. The full framework is set out in the Unified Model of Tone.

11Where this sits

How This Page Relates to the Rest of the Library

Seven places this argument continues, each with the claim that earns the link.

12Questions athletes ask

Questions Athletes Ask

13The sources

References

14 primary sources, each linked to its record. Figures quoted on this page were checked against the published abstract.