Neck Muscular Strength, Training, Performance and Sport Injury Risk: A Review

Evaluating Neck-Strengthening Protocols to Reduce the Incidence of Traumatic Brain Injury: Traditional vs. Nontraditional Neck-Strengthening Techniques

ABSTRACT

Schroeder, LH, McDaniel, AT, Wang, Y, Dickens, GM, Pantani, V, and Kubinak, H. Evaluating neck-strengthening protocols to reduce the incidence of traumatic brain injury: traditional vs. nontraditional neck-strengthening techniques. J Strength Cond Res 38(7): 1266-1274, 2024-A common cause of traumatic brain injuries (TBIs) is the head's kinematic response to rapid movement, which can be reduced with dynamic neck strengthening. This study aimed to determine the most effective neck-strengthening program by comparing a traditional and nontraditional program. Isometric neck strength was assessed in 32 subjects randomly assigned to one of the traditional and nontraditional neck-strengthening programs. The nontraditional program used a novel neck-strengthening device. After weeks 6 and 10 of training, isometric neck strength was reassessed. With the collected data, linear mixed models were established to compare the changes in neck strength between the 2 groups during the 10-week training period. Statistical analysis results suggest that, for both cervical extension (CE) and cervical flexion (CF), subjects in the novel neck-strengthening device group had a significantly higher gain of strength during the 10 weeks than the traditional group. With test statistics of -2.691 and -3.203 and corresponding 2-sided p -value of 0.01289 and 0.003889, respectively, we conclude that there is a statistically significant difference in the linear slopes of increase for both CE and CF between the 2 groups. As to left cervical lateral flexion and right cervical lateral flexion, the novel neck strength group had increased strength gains compared with the traditional group. However, the increase was not enough to demonstrate significant findings. Results were considered significant at p < 0.05. The results of this study show that the novel neck-strengthening device may be an effective mechanism for preventing mild TBIs.

Neck strength alone does not mitigate adverse associations of soccer heading with cognitive performance in adult amateur players

OBJECTIVES

Soccer heading is adversely associated with neurocognitive performance, but whether greater neck strength or anthropometrics mitigates these outcomes is controversial. Here, we examine the effect of neck strength or anthropometrics on associations of soccer heading with neurocognitive outcomes in a large cohort of adult amateur players.

METHODS

380 adult amateur league soccer players underwent standardized measurement of neck strength (forward flexion, extension, left lateral flexion, right lateral flexion) and head/neck anthropometric measures (head circumference, neck length, neck circumference and neck volume). Participants were assessed for heading (HeadCount) and cognitive performance (Cogstate) on up to 7 visits over a period of two years. Principal components analysis (PCA) was performed on 8 neck strength and anthropometric measures. We used generalized estimating equations to test the moderation effect of each of the three PCs on 8 previously identified adverse associations of 2-week and 12-month heading estimates with cognitive performance (psychomotor speed, immediate verbal recall, verbal episodic memory, attention, working memory) and of unintentional head impacts on moderate to severe central nervous system symptoms.

RESULTS

3 principal components (PC's) account for 80% of the variance in the PCA. In men, PC1 represents head/neck anthropometric measures, PC2 represents neck strength measures, and PC3 represents the flexor/extensor (F/E) ratio. In women, PC1 represents neck strength, PC2 represents anthropometrics, and PC3 represents the F/E ratio. Of the 48 moderation effects tested, only one showed statistical significance after Bonferroni correction, which was not robust to extensive sensitivity analyses.

CONCLUSION

Neither neck strength nor anthropometrics mitigate adverse associations of soccer heading with cognitive performance in adult amateur players.

The association of range of motion, lower limb strength, and load during jump landings in professional ballet dancers

This study aimed to investigate the associations between peak plantarflexion ankle joint moments and vertical ground reaction forces (vGRF) during jump landings, and static ankle dorsiflexion range of motion (ROM), three-dimensional ankle excursions, and lower extremity strength in professional ballet dancers. Twenty-seven professional ballet dancers volunteered to participate (men = 14, women = 13). Participants attended one data collection session to measure dorsiflexion ROM and isometric lower extremity strength. Two further sessions were used to establish ankle mechanics and vGRFs during countermovement jump landings in seven foot positions, via a seven-camera motion capture system and piezoelectric force platform. Two linear mixed-effects models were used to investigate associations between the target variables and strength, dorsiflexion ROM, and ankle excursions. Dancer identification, sex, and foot position were entered as random effects. Model fit, when considered independent of random effects, was generally poor with the predictor variables explaining little of the variance of peak plantarflexion ankle joint moments (R2 = 0.02) or vGRF (R2 = 0.01). Model fit improved when random effects were considered (R2 = 0.65 & 0.34). Frontal plane ankle excursion was the only predictor variable with a significant negative association with peak plantarflexion ankle joint moments (p = .016), although coefficient estimates were small. Strength, static ankle dorsiflexion ROM, and three-dimensional ankle excursions are poor predictors of load experienced at a joint and system level in professional ballet dancers. Differences between individuals, sex, and foot position may be better indicators of the load experienced during jump landings.

Predictive Contribution of the Superficial Neck Muscles to Short-Latency Rate of Force Development of the Head and Neck

PURPOSE

To evaluate the contribution of splenius capitis, sternocleidomastoid, and upper fibers of trapezius activation to the gains in rate of force development (RFD) of the head and neck during maximum voluntary ballistic contractions.

METHODS

RFD gain was facilitated by a single-session intervention for maximum voluntary ballistic contractions in the anterior direction, oriented at 45° to the midsagittal plane, which require active restraint of axial rotation. Muscle activation for the agonist (sternocleidomastoid) and 2 antagonists (splenius capitis and upper fibers of trapezius) was evaluated. The study sample included 12 physically active men (mean age, 22.6 y). RFD (N·m·s-1; 0-100 ms) and integrated muscle activity (50 ms before and 100 ms after force onset) were measured at 10 minutes, 20 minutes, and 2 days postintervention, relative to baseline. Muscle activation predictive of RFD gains was evaluated by linear regression analysis. RFD reproducibility was evaluated using the coefficient of variation of the typical error.

RESULTS

The intervention yielded a 1.95- to 2.39-fold RFD gain (P ≤ .05), with greater RFD gain for participants with a lower peak moment of force (<10.9 N·m) than those with a higher peak moment (≥10.9 N·m) at baseline (P ≤ .002). For the low group, 65% to 74% of the RFD gain was predicted by ipsilateral sternocleidomastoid activation, with ipsilateral splenius capitis activation predicting 77% to 92% of RFD gain for the high group. Absolute peak and impulse of static force were greater for the high than for the low group (P ≤ .04). RFD reproducibility was high (coefficient of variation of the typical error ≤ 14.4%).

CONCLUSIONS

The agonist- and antagonist-focused synergies might reflect different functional priorities, higher RFD gain compared with higher head-neck force.

The Relationship of Anthropometric and Physical Performance Characteristics on Competitive Success in Amateur, Elite, and Professional Rodeo Athletes

ABSTRACT

Oranchuk, DJ, Gullett, LK, Kicia, M, Thome, B, and Game, A. The relationship of anthropometric and physical performance characteristics on competitive success in amateur, elite, and professional rodeo athletes. J Strength Cond Res 37(7): 1495-1506, 2023-Reference anthropometric and physical performance qualities can improve understanding of sporting needs and streamline preparation and rehabilitation programs. However, these data and their relationships with competitive success are absent in rodeo athletes. We hypothesized that riding performance would be most correlated with hip adductor, neck, and grip strength, whereas jump, reactive strength index (RSI), and change of direction abilities would best predict bull-fighting performance. Forty-three amateur ( n = 9), professional ( n = 23), or internationally ranked ( n = 11) male rodeo athletes (bareback = 9, bull riders = 16, saddle bronc = 7, bullfighters = 11) (26.8 ± 5.6 years) volunteered for this study. Anthropometrics included body mass, height, and body fat percentage. Performance measures included isometric hip adduction and abduction, neck flexion and extension, handgrip strength, squat and countermovement jump heights, eccentric utilization ratio, reactive strength index, change of direction, bike sprints, and several pneumatic power measures. Bullfighters were taller and heavier than bull riders (effect size [ES] = 0.84-0.87, p = 0.008-0.017). Bull riders were leaner than bullfighters (ES = 0.74, p = 0.012). Fighters had greater RSI than riders (ES = 0.73-1.47, p < 0.001-0.030). Competitive level of rodeo riders ( n = 32) correlated with age, rodeo experience (ρ = 0.37-0.43, p = 0.013-0.049), bent-leg abduction (ρ = 0.43, p = 0.014), straight-leg hip adduction and abduction (ρ = 0.49-0.56, p < 0.001-0.005), neck flexion force (ρ = 0.43, p = 0.016), and rotational power (ρ = 0.50, p = 0.004). The competitive level of the fighters correlated with age (ρ = 0.64, p = 0.036) and time trial performance (ρ = -0.76, p = 0.006). This is the first study providing normative and correlational strength and power performance data in a rodeo population. These data highlight the need for more event-specific physical preparation. Riders should focus their physical preparation on hip and neck strength and rotational power. Bullfighters should prioritize stiffness and anaerobic power.

An Evaluation Study of a New Designed Oscillating Hydraulic Trainer of Neck

In view of the importance of neck strength training and the lack of adequate training equipment, this study designed a new oscillating hydraulic trainer (OHT) of neck based on oscillating hydraulic damper. We used surface electromyography (sEMG) and subjective ratings to evaluate the neck OHT and compared the results with a simple hat trainer (HATT) and traditional weight trainer (TWT) to verify the feasibility and validity of the OHT. Under similar exercise conditions, 12 subjects performed a set of neck flexion and extension exercise with these 3 trainers. The sEMG signals of targeted muscles were collected in real time, and subjects were asked to complete subjective evaluations of product usability after exercise. The results showed that the root mean square (RMS%) of sEMG indicated that the OHT could provide two-way resistance and train the flexors and extensors simultaneously. The overall degree of muscle activation with OHT was higher than that with the other two trainers in one movement cycle. In terms of resistance characteristics exhibited by the sEMG waveform, duration (D) with OHT was significantly longer than HATT and TWT when exercising at a high speed, while Peak Timing (PT) was later. The ratings of product usability and performing usability of OHT were remarkably higher than that of HATT and TWT. Based on the above results, the OHT was proved to be more suitable for strength training, such as neck muscles, which were getting more attention gradually, but lacked mature and special training equipment.

Intra and Inter-Rater Reliability of a Novel Isometric Test of Neck Strength

There is no single, universally accepted method of measuring isometric neck strength to inform exercise prescription and injury risk prediction. This study aimed to establish the inter- and intra-rater reliability of a commercially available fixed frame dynamometer in measuring peak isometric neck strength. A convenience sample of male (n = 16) and female (n = 20) university students performed maximal isometric contractions for flexion (Flex), extension (Ext), left- (LSF) and right-side flexion (RSF) in a quadruped position over three sessions. The intra-rater reliability results were good-to-excellent for both males (ICC = 0.83−0.90) and females (ICC = 0.86−0.94) and acceptable (CV < 15%) across all directions for both males and females. The inter-rater reliability results were excellent (ICC = 0.96−0.97) and acceptable (CV < 11.1%) across all directions. Findings demonstrated a significant effect for sex (p ≤ 0.05): males were stronger in all four directions, and a significant effect for direction (p ≤ 0.05): Ext tested stronger (193 N) than Flex (176 N), LSF (130 N) and RSF (125 N). The findings show that the VALD fixed frame dynamometer can reliably assess isometric neck strength and can provides reference values for healthy males and females.

EFFECT OF STRENGTH TRAINING ON NECK INJURIES PREVENTION IN MARTIAL ARTS ATHLETES

ABSTRACT Introduction: As competitive martial arts develop rapidly, technical difficulty and training intensity continues increasing, neck injuries in athletes have also increased proportionally, attracting the attention of researchers. Localized strength training is used for rehabilitation, but there is no research related to prevention in athletes. Objective: Explore the neck strength training effect on neck injury prevention in martial arts athletes. Methods: 68 (34 male) volunteers attended the experiment randomly divided into control and experimental groups. Traditional training activities were practiced in the control group, while a strength training protocol was added in the experimental group. Indices of change in pain, motor quality, and neck disability index were compared. Results: After the test, the number of neck injuries in the control group was 23, compared to five in the experimental group; there is a significant difference. There was a significant reduction of injuries in the experimental group (P=0.05); one year later, the VAS score of the experimental group remained significantly lower than the same pre-experiment or control group. The neck dysfunction score of the experimental group was still significantly lower than the pre-experimental and control group; there was no statistically significant difference between the control group and the experimental group before the experiment. Conclusion: The adequate periodic neck strength training formulation has a significant preventive effect on neck injuries in martial arts athletes. Evidence Level II; Therapeutic Studies - Investigating the result.

A randomized controlled trial concerning the implementation of the postural Mézières treatment in elite athletes with low back pain

OBJECTIVE

This study aimed to evaluate the impact of adding the Mézières Method (MM) to the standard rehabilitation protocol for the elite athletes with low back pain (LBP) in reducing lumbar pain than only using the traditional rehabilitation protocol treatment. The disciplines considered in this study were soccer, rhythmic gymnastics, and basketball.

DESIGN

Randomized controlled trial.

SETTING

Training Camp.

PARTICIPANTS

One hundred thirty-nine elite athletes with low back pain of whom 69 were assigned to the experimental group.

INTERVENTION

The intervention consists of treatment with three lying postures in a 40-minutes long session twice a week. The session goal was to focus on breathing exercises, spine mobility, and stretching of the back muscles, with particular attention to the diaphragmatic, paravertebral, and latissimus dorsi muscles.

OUTCOME MEASURES

Assessments as Visual Analogue Scale (VAS), Sit and Reach flexibility test, Roland-Morris Questionnaire, and health status questionnaire (SF12) were used.

RESULTS

The evaluation of all outcomes in 4 measurement periods of the study (baseline, 4, 12, and 24 weeks) showed a significant difference between groups. Also, at the 6-month of the intervention, a significant difference in the means (SD) was observed in pain (VAS), back flexibility (Sit & Reach) and back disability (QRM) outcomes in favor of the experimental group with a medium-large effect size comparing with the control group.

CONCLUSION

The MM approach can also be applied in established conventional protocols to alleviate pain and functionality. The obtained results include improving the quality of life of the athletes and their physical and emotional states.

Clinical trial registration number ID: NCT03849053.

Head and Neck Characteristics as Risk Factors For and Protective Factors Against Mild Traumatic Brain Injury in Military and Sporting Populations: A Systematic Review

BACKGROUND

Investigators have proposed that various physical head and neck characteristics, such as neck strength and head and neck size, are associated with protection from mild traumatic brain injury (mTBI/concussion).

OBJECTIVES

To systematically review the literature and investigate potential relationships between physical head and neck characteristics and mTBI risk in athletic and military populations.

METHODS

A comprehensive search of seven databases was conducted: MEDLINE, EMBASE, CINAHL, Scopus, SPORTDiscus, Cochrane Library, and Web of Science. Potential studies were systematically screened and reviewed. Studies on military and athletic cohorts were included if they assessed the relationship between physical head-neck characteristics and mTBI risk or proxy risk measures such as head impact kinematics.

RESULTS

The systematic search yielded a total of 11,723 original records. From these, 22 studies met our inclusion criteria (10 longitudinal, 12 cross-sectional). Relevant to our PECO (Population, Exposure, Comparator, and Outcomes) question, exposures included mTBI incidence and head impact kinematics (acceleration, velocity, displacement) for impacts during sport play and training and in controlled laboratory conditions. Outcome characteristics included head and neck size (circumference, mass, length, ratios between these measures), neck strength and endurance, and rate of force development of neck muscles.

DISCUSSION

We found mixed evidence for head and neck characteristics acting as risk factors for and protective factors against mTBI and increased susceptibility to head impacts. Head-neck strength and size variables were at times associated with protection against mTBI incidence and reduced impact kinematics (14/22 studies found one or more head-neck variable to be associated with protection); however, some studies did not find these relationships (8/22 studies found no significant associations or relationships). Interestingly, two studies found stronger and larger athletes were more at risk of sustaining high impacts during sport. Strength and size metrics may have some predictive power, but impact mitigation seems to be influenced by many other variables, such as behaviour, sex, and impact anticipation. A meta-analysis could not be performed due to heterogeneity in study design and reporting.

CONCLUSION

There is mixed evidence in the literature for the protective capacity of head and neck characteristics. We suggest field-based mTBI research in the future should include more dynamic anthropometric metrics, such as neck stiffness and response to perturbation. In addition, laboratory-based mTBI studies should aim to standardise design and reporting to help further uncover these complicated relationships.

A Systematic Review on the Biomechanics of Breakfall Technique (Ukemi) in Relation to Injury in Judo within the Adult Judoka Population

Objectives: To investigate the biomechanics of Ukemi in relation to head and neck injury in adult judokas with varying skill sets. Design: Narrative systematic review. Methods: An extensive literature search was performed using PubMed, Google Scholar, Science direct and EMBASE from inception to April 2021. Studies were included if they: (1) reported biomechanical analysis of judo throws and Ukemi; (2) were on adult judoka populations; (3) discussed injury related to judo technique. The included studies were assessed for risk of bias using a five-part modified STROBE checklist. A narrative synthesis was performed due to the heterogeneity of included studies. Results: 173 titles and abstracts were screened with 16 studies (158 judokas, 9 of which were female) included. All studies used 3D biomechanical analysis to assess Ukemi. Ukemi implementation produced reduced kinematic data in comparison to direct occipital contact, which was always below the injury threshold. Analysis of lower limb and trunk kinematics revealed variances in Ukemi between novice and experienced judoka. Whilst no significant differences were seen in neck flexion angles, hip, knee and trunk angle time plots revealed greater extension angles in experienced judokas. Conclusions: Ukemi is essential in preventing head and neck injuries; however, technique differs between experienced and novice judoka. Larger flexion angles of the hip, knee and trunk are seen in novice judoka, which correlate with increased kinematic data. The association of greater neck muscle strength with improved Ukemi is weak. However, a negative correlation was established between fatigue and breakfall skill by one study.

Why the patients with Hirayama disease have abnormal cervical sagittal alignment? A radiological measurement analysis of posterior cervical extensors

PURPOSE

To explore the relationship between the strength of posterior cervical extensors (PCEs) and cervical sagittal alignment in Hirayama disease (HD) patients.

METHODS

We analyzed the (magnetic resonance imaging) MRI T2WI and X-rays of 60 HD patients who visited Huashan Hospital from June 2017 to February 2020. Symptoms of these patients include adolescent onset, manifestation of unilateral upper limb muscle weakness and muscle atrophy of the forearm and hand. MRI images were used to measure (the cross-sectional area) CSA of cervical PCEs. The ratio of muscle CSA to vertebral body areas at the same level is defined as R-CSA. Cervical sagittal alignment includes the C_2-7 Cobb angle, T1 slope and C_2-7 sagittal vertical axis (SVA). The geometric center of the C_3-6 vertebral body was determined using the line connecting the C₂ inferior endplate and the C₇ upper endplate. When located behind the line, it is defined as a "local kyphotic deformity." The number of vertebral bodies involved in kyphotic deformity was determined by measuring the local kyphosis angle (LKA). Spearman correlation analysis (α = 0.05) was used to determine the relationship between R-CSA and sagittal parameters. ROC curves were used to analyze the sensitivity and specificity of relevant variables.

RESULTS

Spearman correlation test revealed that R-CSA negatively correlated with T1S (S = 0.34, r = 0.34, p = 0.01) and LKA (S = 0.44, r = 0.5, p = 0.01), but did not correlate with the C2-C7 Cobb angle (S = 0.20, p = 0.12) or C2-C7 SVA (S =  - 0.17, p = 0.46). (p < 0.05). ROC curve analysis showed that the areas under the curve (AUCs) of the T1 slope and LKA was 0.6696 and 0.7646, respectively. T1 slope, cutoff value: 17.2°; sensitivity: 0.5806; specificity: 0.7241; p < 0.05. LKA: cutoff value: - 14°; sensitivity: 1; specificity: 0.5333; p < 0.05.

CONCLUSIONS

In patients with Hirayama disease, the strength of posterior cervical extensors and cervical sagittal alignment are closely related. The local kyphosis angle can be used as a reference for the strength of posterior cervical extensors. These results indicate the weakness of PCEs, which may predispose the cervical spine of HD patients to a less stable situation. Therefore, patients with Hirayama disease should strengthen the exercise of the PCEs.

Investigation of Aerobic and Muscular Fitness and Concussion Among Service Academy Cadets at the United States Air Force Academy: Results from the CARE Consortium

INTRODUCTION

Concussion has become the signature injury facing the U.S. military. However, little is understood about the relationship between military fitness and concussion recovery. The current study examined the recoveries of cadets at a U.S. Service Academy to determine whether preinjury physical fitness improved recovery and whether recovery was associated with post-injury physical fitness measures.

METHODS

Participants were enrolled in a longitudinal study of concussion. Aerobic Fitness Test (AFT) and Physical Fitness Test (PFT) data were used to estimate cadet fitness. Survival analysis evaluated significant estimators of concussion recovery time. Linear regression models were used to explore the relationship between recovery duration and change in physical fitness scores.

RESULTS

Between 2014 and 2017, 307 (n = 70; 22.80% Women) cadets who had sustained a concussion were enrolled. Preinjury physical fitness was not significantly associated with recovery duration (P > .05). Men and intercollegiate cadets took fewer days to reach recovery milestones. Compared to women, men had greater decrements in the Aerobic Fitness Test total score (P < .05) and increased 1.5-mile time postconcussion (P < .05). Women had greater decreases in push-ups postconcussion compared to males (P < .05). There was a trend for a negative association between days until asymptomatic and change in the Physical Fitness Test score (P = .07).

CONCLUSION

Preconcussion physical fitness levels do not appear to impact concussion recovery time among a highly physically fit cohort. Possible methods to reduce the effect of symptom duration on strength-related physical fitness should be investigated along with evaluating reductions in strength as a possible mechanism for postconcussion injury risk.

Neck strength in Rugby Union players: a systematic review of the literature

The incidence and severity of concussion injuries are increasing every year. Scientific evidence indicates that neck strength and girth could play a role in preventing head and neck injuries, or at least mitigating their severity. We aimed to examine the scientific literature addressing neck strength in Rugby Union with a focus on the potential role of neck strength on injury incidence, neck assessment protocols, neck strength measures, and neck strengthening exercises.We conducted a systematic search of the literature in January 2021 to locate published peer-reviewed articles from PubMed, SPORTDiscus^TM, Web of Science®, and Scopus® e-databases. Overall, senior elite male players were stronger than younger-aged players. Forwards were stronger in extension than any other directions assessed, and were generally stronger and possessed larger necks and greater cross-sectional areas when compared to backs. Implementation of isometric exercise routines in professional players was reported to improve neck strength in all directions. There were no studies evaluating the incidence of concussion and neck strength or neck strengthening strategies in Rugby Union. Strengthening the neck continues to be one of the targeted modifiable risk factors with respect to limiting the severity and temporal effects of head injuries in Rugby Union, despite limited evidence regarding direct associations between neck strength and concussion.

An Accessible, 16-Week Neck Strength Training Program Improves Head Kinematics Following Chest Perturbation in Young Soccer Athletes

CONTEXT

Neck size and strength may be associated with head kinematics and concussion risks. However, there is a paucity of research examining neck strengthening and head kinematics in youths. In addition, neck training is likely lacking in youth sport due to a perceived inadequacy of equipment or time.

OBJECTIVE

Examine neck training effects with minimal equipment on neck strength and head kinematics following chest perturbations in youth athletes.

DESIGN

Single-group, pretest-posttest case series.

SETTING

Athlete training center.

PARTICIPANTS

Twenty-five (14 men and 11 women) youth soccer athletes (9.8 [1.5] y).

INTERVENTION

Sixteen weeks of twice-weekly neck-focused resistance training utilizing bands, body weight, and manual resistance.

MAIN OUTCOME MEASURES

Head kinematics (angular range of motion, peak anterior-posterior linear acceleration, and peak resultant linear acceleration) were measured by an inertial motion unit fixed to the apex of the head during torso perturbations. Neck-flexion and extension strength were assessed using weights placed on the forehead and a plate-loaded neck harness, respectively. Neck length and circumference were measured via measuring tape.

RESULTS

Neck extension (increase in median values for all: +4.5 kg, +100%, P < .001; females: +4.5 kg, +100%, P = .002; males: +2.2 kg, +36%, P = .003) and flexion (all: +3.6 kg, +114%, P < .001; females: +3.6 kg, +114%, P = .004; males: +3.6 kg, +114%, P = .001) strength increased following the intervention. Men and women both experienced reduced perturbation-induced head pitch (all: -84%, P < .001). However, peak resultant linear acceleration decreased in the female (-53%, P = .004), but not male (-31%, P = 1.0) subgroup. Preintervention peak resultant linear acceleration and extension strength (R2 = .21, P = .033) were the closest-to-significance associations between head kinematics and strength.

CONCLUSIONS

Young athletes can improve neck strength and reduce perturbation-induced head kinematics following a 16-week neck strengthening program. However, further research is needed to determine the effect of improved strength and head stabilization on concussion injury rates.

Sex and posture dependence of neck muscle size-strength relationships

Neck muscle size and strength have been linked to lower injury risk and reduced pain. However, prior findings have been inconclusive and have failed to clarify whether there are sex differences in neck muscle size-strength relationships. Such differences may point to an underlying cause for the reported sex difference in neck pain prevalence. Thirty participants (13 males, 17 females) who underwent neck strength testing and MR imaging were analyzed. Strength was measured in three conditions that differed in posture and exertion direction. Muscle size was quantified by three metrics: anatomical cross-sectional area (ACSA), muscle volume (MV), and an estimate of physiological cross-sectional area-reconstruction-based cross-sectional area (RCSA). Inter-posture strength correlations, muscle size-strength correlations, and sex differences were analyzed with linear regression. Males were approximately 65% stronger and had significantly larger muscles. Strength varied significantly across postures, but only female strength values for different postures were significantly correlated. Observed in males only, the sternocleidomastoid (SCM) was a strong predictor of flexion strength in the neutral posture while the anterior scalene (AS) was more involved in the extended. No extensor's size was significantly linked to extension strength. A greater amount of force variation is unexplained by muscle size alone in females than in males. Males and females exhibited distinct size-strength relationships, highlighting the need for sex-specific models and analyses and the greater potential effect of non-morphometric factors on force generating capacity in females. No advantage of one muscle size metric over another in strength prediction was evidenced.

Injury Reduction Programs for Reducing the Incidence of Sport-Related Head and Neck Injuries Including Concussion: A Systematic Review

BACKGROUND

Sport-related head and neck injuries, including concussion, are a growing global public health concern with a need to explore injury risk reduction strategies such as neck exercises.

OBJECTIVES

To systematically review the literature to investigate: (1) the relationship between neck strength and sport-related head and neck injuries (including sport-related concussion (SRC); and (2) whether neck exercise programs can reduce the incidence of (a) sport-related head and neck injuries; and (b) SRC.

METHODS

Five databases (Ovid MEDLINE, CINAHL, EMBASE, SPORTDiscus, and Web of Science) and research lists of included studies were searched using a combination of medical subject headings and keywords to locate original studies which reported the association between incidence of head and/or neck injury and neck strength data, or included a neck exercise intervention either in isolation or as part of a more comprehensive exercise program.

RESULTS

From an initial search of 593 studies, six were included in this review. A narrative synthesis was performed due to the heterogeneity of the included studies. The results of two observational studies reported that higher neck strength, but not deep neck flexor endurance, is associated with a lower risk of sustaining a SRC. Four intervention studies demonstrated that injury reduction programs that included neck exercises can reduce the incidence of sport-related head and neck injuries including SRC.

CONCLUSION

Consideration should be given towards incorporating neck exercises into injury reduction exercise programs to reduce the incidence of sport-related head and neck injuries, including SRC.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO (registration number: 194217).

The relation between neck strength and psychological distress: preliminary evidence from collegiate soccer athletes

AIM

To examine whether neck strength and symmetry are associated with psychological function in athletes with exposure to repetitive head impacts.

METHODS

Collegiate soccer (n = 29) and limited/noncontact (n = 63) athletes without a history of concussion completed the Brief Symptom Inventory 18 and assessments of isometric neck strength. Neck strength symmetry was calculated as the difference in strength between opposing muscle groups.

RESULTS

The results demonstrated that lower neck strength was associated with more symptoms of anxiety, whereas asymmetry in neck strength was associated with more symptoms of somatization and depression in soccer athletes only.

CONCLUSION

These preliminary results suggest that greater neck strength/symmetry is related to better psychological function in athletes who have higher exposure to repetitive head impacts.

Head impact forces in blind football are greater in competition than training and increased cervical strength may reduce impact magnitude

Paralympic Blind Association Football has the highest rate of injury of any Paralympic sport and head injuries are common. This study aims to quantify head impact incidence and magnitude in Blind Football, and to examine contributing factors. This Observational study based on a Blind Football Team comprising seven male athletes 28.63 years (SD 9.74, range 16-46) over 6 months. Head mounted impact sensors were used to measure the frequency and location of impacts, as well as their linear acceleration and rotational velocity. Cervical isometric strength and proprioception was measured. There were 374 impacts recorded in 212.5 athlete hours. There was a higher rate of impacts in matches than training (Incidence Risk Ratio 2.58, 95% CI 2.01-3.30). Greater cervical strength was associated with reduced linear acceleration of impacts (R² = 0.1912, p = .020). Blind Football players are exposed to a greater number of head impacts in matches than training. Neck muscle strength may influence magnitude of head impact forces in this sport but further study is required to further investigate.

Concurrent Validity and Reliability of a Low-Cost Dynamometer to Assess Maximal Isometric Strength in Neck Movements

OBJECTIVE

This study aimed to evaluate the concurrent validity and reliability of a low-cost digital dynamometer to assess maximal isometric strength in neck movements.

METHODS

Twelve recreationally active participants (6 women, 6 men; age: 24.1 ± 3.4 years; height: 1.71 ± 0.06 m; weight: 64.6 ± 11.7 kg) performed neck flexion, extension, and lateral flexion, and maximal isometric strength was simultaneously measured using an isokinetic dynamometer (gold standard) and a digital dynamometer to evaluate the concurrent validity of the latter. One week later, all the participants repeated 3 trials of each neck movement (3 minutes apart) registered only with the digital dynamometer. The first and second trial were guided by tester 1 and the third trial was guided by tester 2.

RESULTS

The concurrent validity of the digital dynamometer showed a nearly perfect correlation between both devices (r > 0.986, P < .001), with Bland-Altman plots showing absolute agreement. Intertester and intratester reliability were nearly perfect for all neck movements (intraclass correlation coefficient > 0.86).

CONCLUSION

The low-cost digital dynamometer showed valid and reliable measurements of maximal isometric strength in neck movements.

A Systematic Review of Strength and Conditioning Protocols for Improving Neck Strength and Reducing Concussion Incidence and Impact Injury Risk in Collision Sports; Is There Evidence?

The objective of this systematic literature review was to evaluate the evidence regarding the development of neck strength in reducing concussion and cervical spine injuries in adult amateur and professional sport populations. PubMed, CINAHL, Science Direct, and Web of Science databases were searched systematically. The criteria for inclusion in the review were as follows: (1) a human adult (≥18 or above); (2) involved in amateur, semi-professional, or professional sports; (3) sports included involved collisions with other humans, apparatus or the environment; (4) interventions included pre- and post-neck muscle strength measures or neck stability measures; (5) outcomes included effects on increasing neck strength in participants and/or injury incidence. Database searches identified 2462 articles. Following title, abstract, and full paper screening, three papers were eligible for inclusion. All of the papers reported information from male participants, two were focused on rugby union, and one on American football. Two of the included studies found a significant improvement in isometric neck strength following intervention. None of the studies reported any impact of neck strengthening exercises on cervical spine injuries. This review has shown that there is currently a lack of evidence to support the use of neck strengthening interventions in reducing impact injury risk in adult populations who participate in sport.

Isometric Cervical Muscular Strength in Pediatric Athletes With Multiple Concussions

OBJECTIVE

To compare maximal cervical muscle strength among athletes with a history of 2 or more concussions relative to athletes with no history of a previous concussion.

DESIGN

Athletes in the 2 groups were frequency-matched. Linear mixed models were used to test for differences in peak isometric flexion, extension, left lateral flexion, and right lateral flexion cervical muscle torque between groups.

SETTING

Pediatric sports medicine clinic.

PARTICIPANTS

Athletes with a history of multiple concussions (n = 16) and athletes with no previous concussion history (n = 17). INTERVENTIONS (OR ASSESSMENT OF RISK FACTORS OR INDEPENDENT VARIABLES):: Concussion history (group), age, sex, neck girth, and height.

MAIN OUTCOME MEASURES

Peak isometric torque measured with a stationary isokinetic dynamometer during a 3-second isometric hold.

RESULTS

There was no significant difference in peak flexion [mean difference: 21.2%, 95% confidence interval (CI): -6.6% to 57.4%, P = 0.1413], extension (mean difference: 17%, 95% CI, -6.8% to 47.1%, P = 0.1667), left lateral (mean difference: 4.4%, 95% CI, -16.9% to 31.1%, P = 0.7011), or right lateral (mean difference: 9.3%, 95% CI, -14.5% to 39.8%, P = 0.4627) isometric torque in the concussion group relative to the control group. Across all muscle actions, neck torque was significantly (P < 0.05) higher in male compared with female athletes. Increasing neck girth was also associated with a significant (P < 0.05) increase in neck torque.

CONCLUSIONS

There was no evidence of a consistent cervical muscle strength deficit among athletes with a history of 2 or more concussions relative to athletes with no previous history of a concussion. Age, neck girth, and sex were significantly associated with cervical muscle strength.

CLINICAL RELEVANCE

Isometric cervical muscle strength testing may not be a reliable test for differentiating athletes with a history of multiple concussions relative to athletes with no history of concussions in the pediatric and adolescent population. Our study presents a reliable methodology for testing cervical muscle strength among young athletes.

Endurance of the Dorsal and Ventral Muscles in the Neck

Endurance of the muscles of the neck are rarely studied. This study measured the endurance index (EI) of the sternocleidomastoid (SCM) and upper trapezius muscles of the neck (trap). The vastus lateralis (VL) was used for comparison. Skeletal muscle endurance of twelve healthy subjects, age 19-22 years, were tested on their SCM and trap in random order on one day, VL was tested on a separate day. Participants were tested in the supine position for the SCM and VL muscles and the prone position for the trap. Muscle contractions consisted of a 5 Hz twitch electrical stimulation for 5 min. Muscle acceleration (resultant vector) was measured using a triaxial accelerometer. EI was the ending acceleration as a percentage of the maximal acceleration. The endurance index (EI) for the SCM, trap, and VL was 42.3 ± 13.0%, 42.3 ± 20.2%, and 92.9 ± 11.0%, respectively. The EI of the VL was significantly higher than the EI of the SCM (t(2,22) = 10.33, p < 0.001) and the trap (t(2,22) = 7.625, p < 0.001). The EI was not different between the SCM and the trap muscle (t(2,22) = 0.004, p = 0.997). In conclusion, the neck muscles had much less endurance than the muscles in the leg and could make fatigued athletes more susceptible to concussions caused by head impacts.

A Novel Testing Device to Assess the Effect of Neck Strength on Risk of Concussion

Concussion awareness has become more prevalent in the past decade, leading to growing calls for prevention programs such as neck strengthening. However, previous research work has shown that not all training programs have been effective, and there is a need for a reliable testing device to measure cervical strength dynamically before and after training. Therefore, this work proposes a novel Concussion Active Prevention Testing Device composed of inertial measurement units mounted on the head and a custom-designed frame to measure head kinematics during controlled sub-concussive impacts. Through an experimental study with able-bodied participants, the proposed testing device demonstrated high intra-participant repeatability between waveforms of the head acceleration and angular velocity in the sagittal plane (multiple correlation coefficient of 80%). Similarly, good and excellent intra-class correlation coefficients were obtained for head injury metrics, including range, peak, Gadd severity index, head injury criterion, and range of motion. Finally, the results showed that significantly higher head injury metrics were measured for female participants, which was in line with the findings of previous research works. We conclude that the proposed testing device can be used to measure repeatable and informative metrics for evaluating the effectiveness of athletes' neck strengthening program.

Match Situations Leading to Head Injuries in Professional Male Football (Soccer)-A Video-Based Analysis Over 12 Years

OBJECTIVE

To identify risk situations promoting head injuries in professional male football (soccer) and to investigate the impact of a rule change in 2006 punishing elbow-head contacts.

DESIGN

Analysis of video sequences of head events leading to head injury.

PARTICIPANTS

Professional football players of the first male German Bundesliga.

MAIN OUTCOME MEASURES

Observational criteria of head impacts on video recordings (players' actions preceding head injuries, foul play-referee's decision and assessment of rater, ball possession, on-pitch medical treatment, and consequences of head impact).

RESULTS

Three hundred thirty-four head injuries were reported in kicker Sportmagazin corresponding to an incidence rate of 2.25 (95% confidence interval 2.01-2.51) per 1000 player match hours. The injured player predominantly jumped (60%), headed the ball (36%), or ran forwards (20%); the noninjured players mainly jumped (64%), headed the ball (27%), or raised the elbow to the head (23%). Free ball situations (2 players challenge for the ball) caused most of the head injuries (81%). The players' action "raising the elbow" during a head injury seemed to be lower after the rule change.

CONCLUSIONS

Jumping for the ball with the intention of heading is the predominant action associated with head injury risk. Head injuries occur most often when players challenge for the ball in a header duel. As head injuries bear the potential risk of long-term health sequelae, the identification of situational circumstances is essential to develop preventative means in the future.

Catastrophic Return to Play in Rugby After Double Cervical Arthrodesis

For high-level athletes, most experts consider that 1-level arthrodesis in cervical spine surgery does not prevent return to play. Nevertheless, return remains controversial in cases of 2-level fusions. We report the case of a 27-year-old professional rugby player. He had had a double cervical fusion C5C6 and C6C7 for cervical hernia and was allowed to continue rugby activities afterward. Four years after this surgery, his neck was forced in hyperflexion during a match and complete tetraplegia occurred. A computed tomography scan showed a C3C4 unilateral facet dislocation. The patient was rapidly operated on. At follow-up, 2 years after the accident, the patient remained tetraplegic with no neurologic improvement. If no definitive conclusion can be established on this first observation, many precautions must be taken before a return-to-play decision, especially in contact sports.

Women and Men Use Different Strategies to Stabilize the Head in Response to Impulsive Loads: Implications for Concussion Injury Risk

BACKGROUND

Cervical musculoskeletal and neuromuscular attributes, which may vary between men and women, influence an individual's capacity to stabilize the head.

OBJECTIVES

To examine sex differences in cervical musculoskeletal and neuromuscular attributes and their impact on head stability. The secondary objective was to examine the effects of anticipation and preload on head kinematics.

METHODS

Thirty-four (20 men, 14 women) recreationally active adult athletes completed a perturbation protocol with anticipation and preloading conditions in this descriptive cross-sectional study. We assessed the neuromuscular response of the sternocleidomastoid to perturbation and head kinematics. We measured neck girth, sternocleidomastoid physiological cross-sectional area, and isometric strength.

RESULTS

Women had smaller neck girth, smaller sternocleidomastoid physiological cross-sectional area, and lower isometric strength than men. Women had greater baseline electromyography (EMG) amplitude and greater peak EMG response than men. There were no sex differences in sternocleidomastoid onset latency or head kinematics. Women had a greater increase in baseline EMG amplitude after preloading and anticipated conditions. Preloading attenuated sex differences in muscle onset latency. Across the sexes, there was a significant main effect of anticipation on head kinematics.

CONCLUSION

Men and women used different strategies to stabilize the head, and responded differently to the preloading and anticipation conditions. J Orthop Sports Phys Ther 2019;49(11):779-786. Epub 15 May 2019. doi:10.2519/jospt.2019.8760.

EPIDEMIOLOGY of NECK INJURIES ACCOMPANYING SPORT CONCUSSIONS in YOUTH OVER a 13-YEAR PERIOD IN a COMMUNITY-BASED HEALTHCARE SYSTEM

Background

The same trauma that produces concussion may also produce neck injury. The signs of concussion and neck injury are similar, and symptoms after acceleration-deceleration trauma to the head-neck complex do not accurately discriminate between them. Research on the epidemiology of neck injury among sport-concussed youth is sparse.

Purpose

The purpose of this study was to investigate the epidemiology of diagnosed neck injury in non-sport-related concussion (Non-SRC) versus sport-related concussion (SRC) in youth by age, sex, and sport.

Study design

Cross-sectional epidemiologic study.

Methods

De-identified data from community-based electronic health records over 13 years were extracted to analyze rates and characteristics of neck injuries among non-SRCs and SRCs in youth aged five to 21. Neck injury diagnosis prevalence rates and odds ratios were calculated to estimate risk of neck injury among concussed youth, comparing non-SRCs to SRCs by age and sex.

Results

Sixteen thousand, eight hundred eighty-five concussion records were extracted, of which 3,040 SRCs and 2,775 non-SRCs in youth aged five to 21 were identified by cross-filtering sport-related keywords (e.g., football, basketball, soccer, running, swimming, batting, horseback riding, skiing, etc.) with all ICD-9 and ICD-10 concussion codes. The prevalence of neck injuries diagnosed among SRCs (7.2%) was significantly different than the prevalence of neck injuries diagnosed among non-SRCs (12.1%, p < 0.000). Neck injury diagnoses were significantly more prevalent in females overall (p < 0.000) and among non-SRCs (p < 0.000). The prevalence of neck injury diagnoses was not significantly higher in concussed females versus concussed males with SRC (p = 0.164).Among youth aged five to 21 exposed to concussions, non-SRCs were more likely to be accompanied by a neck injury diagnosis than SRCs (OR 1.66; 95% CI 1.39 to 1.98; p < 0.000). Similarly, female-to-male neck injury proportion ratios were significantly higher in females in non-SRCs compared to SRCs (IPR 1.90, 95% CI 1.60 to 2.25, p < 0.000).Sports with highest prevalence of concussion differ from sports with highest prevalence of concussion-related neck injury in both sexes.

Conclusions

The overall prevalence of diagnosed neck injuries in youth was higher in non-SRCs compared to SRCs (12.1 vs. 7.2%, p < 0.001), with the highest prevalence at age 14 in both sexes. The risk of neck injury diagnosis accompanying concussion was significantly higher in females compared to males (6.1% difference; p < 0.000).

Evaluating the Effects of a Novel Neuromuscular Neck Training Device on Multiplanar Static and Dynamic Neck Strength: A Pilot Study

Versteegh, TH, Dickey, JP, Emery, CA, Fischer, LK, MacDermid, JC, and Walton, DM. Evaluating the effects of a novel neuromuscular neck training device on multiplanar static and dynamic neck strength: A pilot study. J Strength Cond Res 34(3): 708-716, 2020-The neck serves an important function in damping the transference of acceleration forces between the head and the trunk, such as that occurring during contact sports or motor vehicle collisions. An inability to adequately dissipate forces has been proposed as a potential mechanism for clinical conditions such as whiplash or concussion, but current approaches to neck training may not be targeting the correct mechanisms. The purpose of this study was to explore the training effect of a novel neuromuscular strengthening protocol on dynamic and static neck strength. This was a quasiexperimental pilot study design with intervention (n = 8) and control (n = 10) groups. The intervention group was trained (twice/week, ∼10 minutes, for 7 weeks) on a training device that uses self-generated centripetal force to create a dynamic rotational resistance. This protocol is intended to target the ability of the neck muscles to perform coordinated multiplanar plyometric contractions. Both groups also continued with traditional neck strengthening that included training on a straight-plane, isotonic, 4-way neck machine. Performance on the training device showed improvement after routine practice within 1 week, as evidenced by a trend toward increased peak speed in revolutions per minute (RPM). After 7 weeks, peak RPM increased from 122.8 (95% confidence interval [CI], 91.3-154.4) to 252.3 (95% CI, 241.5-263.1). There was also a large positive effect size (Hedge's d, 0.68) in isometric composite (multiplane) neck strength favoring the intervention group over the control group (difference, 20 N; 95% CI, -8 to 48). The largest magnitude strength improvement in a single plane was in axial rotation and also favored the intervention group over the control group (Hedge's d, 1.24; difference, 46 N; 95% CI, 9-83). Future studies should explore whether the dynamic training presented here could help reduce the risk of sports concussion, whiplash, or other head-neck trauma.

The Potential Role of the Cervical Spine in Sports-Related Concussion: Clinical Perspectives and Considerations for Risk Reduction

Sports-related concussion (SRC) occurs due to biomechanical forces to the head or neck that can result in pathophysiological changes in the brain. The musculature of the cervical spine has been identified as one potential factor in reducing SRC risk as well as for underlying sex differences in SRC rates. Recent research has demonstrated that linear and rotational head acceleration, as well as the magnitude of force upon impact, is influenced by cervical spine biomechanics. Increased neck strength and girth are associated with reduced linear and rotational head acceleration during impact. Past work has also shown that overall neck strength and girth are reduced in athletes with SRC. Additionally, differences in cervical spine biomechanics are hypothesized as a critical factor underlying sex differences in SRC rates. Specifically, compared to males, females tend to have less neck strength and girth, which are associated with increased linear and rotational head acceleration. Although our ability to detect SRC has greatly improved, our ability to prevent SRC from occurring and decrease the severity of clinical outcomes postinjury is limited. However, we suggest, along with others, that cervical spine biomechanics may be a modifiable factor in reducing SRC risk. In this commentary, we review the role of the cervical spine in reducing SRC risk, and how this risk differs by sex. We discuss clinical considerations for the examination of the cervical spine and the potential clinical relevance for SRC prevention. Additionally, we provide suggestions for future research examining cervical spine properties as modifiable factors in reducing SRC risk. J Orthop Sports Phys Ther 2019;49(3):202-208. Epub 15 Jan 2019. doi:10.2519/jospt.2019.8582.

The effects of vision training, neck musculature strength, and reaction time on concussions in an athletic population

A concussion is a major concern across the athletic population. Prevention of concussions can lead to a decrease of 3.8 million concussions that occur annually in the United States. Vision training, increasing neck musculature strength and quick reaction times are thought to be ways to prevent concussions. The purpose of this study is to review the literature on vision training, neck musculature, and reaction time, and how these interventions can prevent concussions. Upon review of the literature, vision training is proven to prevent concussions in a collegiate football setting, but there is no literature on different levels or sports. There are inconclusive results on whether neck musculature strength prevents concussions. There are substantial results concluding reaction time does prevent concussions by allowing the athlete to protect and anticipate head impact lessening the severity of the blow to the head. More research needs to be done for all three interventions to prove across all ages and levels of every sport that vision training, neck musculature strength, and reaction time prevent concussions in an athletic population. If proven true, practitioners in an athletic setting can use vision training, increasing neck musculature strength, and increasing reaction time as interventions to help prevent concussions in an athletic population.

Inconsistent anticipatory postural adjustments (APAs) in rugby players: a source of injuries?

Background

We are developing since 2010 with Thales and the Fédération Française de Rugby (FFR) M-Rex, a new kind of rugby scrum simulator. The study questioned whether it could improve safety and protect players from injury by using it as a tool for training/coaching the packs.

Aim

To explore the anticipatory postural adjustments (APAs) during the engagement of the ruck, because these predictive neck and back muscles contractions protect the spinal cord at the time of impacts, which is crucial to prevent injuries.

Methods

We quantified the kinematics and the EMG activities in high-level front row players during their initial engagement, when scrummaging with M-Rex. All studies were performed with one player interacting with the robot, at first, and then with the three players acting together.

Results

For most of the tested high-level players, the APA latencies were highly variable from trial to trial even though the engagement resulted in similar impacts. At time, the onset of the electromyography activity in the neck and back muscles showed latencies inferior to 50 ms or even close to zero prior to the impact, which rendered muscle contractions inefficient as APAs. We were also unable to identify clear muscular synergies underlying the APAs because of their great variability on a trial-to-trial basis. Finally, the APAs were not related to the amplitude of the ensuing impact and were asymmetric in most trials. All these characteristics held true, whether the player was playing alone or with two other frontline players.

Conclusion

Our result suggest that APAs should be systematically tested in high-level rugby players as well as in any high-level sport men at risk of neck and back injuries. Because APAs can be efficiently trained, our study paves the way to design individual position-specific injury prevention programme.

Predictors of clinical recovery from concussion: a systematic review

OBJECTIVE

A systematic review of factors that might be associated with, or influence, clinical recovery from sport-related concussion. Clinical recovery was defined functionally as a return to normal activities, including school and sports, following injury.

DESIGN

Systematic review.

DATA SOURCES

PubMed, PsycINFO, MEDLINE, CINAHL, Cochrane Library, EMBASE, SPORTDiscus, Scopus and Web of Science.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Studies published by June of 2016 that addressed clinical recovery from concussion.

RESULTS

A total of 7617 articles were identified using the search strategy, and 101 articles were included. There are major methodological differences across the studies. Many different clinical outcomes were measured, such as symptoms, cognition, balance, return to school and return to sports, although symptom outcomes were the most frequently measured. The most consistent predictor of slower recovery from concussion is the severity of a person's acute and subacute symptoms. The development of subacute problems with headaches or depression is likely a risk factor for persistent symptoms lasting greater than a month. Those with a preinjury history of mental health problems appear to be at greater risk for having persistent symptoms. Those with attention deficit hyperactivity disorder (ADHD) or learning disabilities do not appear to be at substantially greater risk. There is some evidence that the teenage years, particularly high school, might be the most vulnerable time period for having persistent symptoms-with greater risk for girls than boys.

CONCLUSION

The literature on clinical recovery from sport-related concussion has grown dramatically, is mostly mixed, but some factors have emerged as being related to outcome.