Head-neck cooling effects on central and peripheral fatigue, motor accuracy, and blood markers of stress in men with multiple sclerosis and healthy men: A randomized crossover study.

BACKGROUND: The present study aimed to investigate whether head and neck cooling (at 18 °C next to the skin) and fatiguing submaximal exercise at a thermoneutral ambient temperature can induce peripheral and central responses in healthy men and those with multiple sclerosis (MS). METHODS: A local head-neck cooling (at 18 °C next to the skin) intervention in men with a relapsing-remitting form of MS (n = 18; age 30.9 ± 8.1 years) and healthy men (n = 22; age 26.7 ± 5.9 years) was assessed. Men in both groups performed 100 intermittent isometric knee extensions with 5 s contractions and 20 s of rest. The primary variables were measured before exercise, after 50 and 100 repetitions, and 1 h after recovery. The central activation ratio, maximal voluntary contraction, electrically induced force, electromyography, contractile properties, blood markers, muscle temperature, and perception of effort were measured. RESULTS: Compared with noncooled conditions, head and neck cooling increased the central capacity to activate exercising muscles but resulted in greater exercise-induced peripheral fatigue in men with MS (p < 0.05). Local cooling did not affect motor accuracy or the amplitude of electromyography signals; however, these factors were related to the intensity of the motor task (p > 0.05). The changes in central and peripheral fatigability induced by local cooling during submaximal exercise were more pronounced in men with MS than in healthy men (p < 0.05). CONCLUSION: Head and neck cooling enhances central activation of muscles during exercise, leading to improved exercise performance compared with noncooled conditions in men with MS.

Forward head posture associated with reduced cardiorespiratory fitness in psychotic disorders compared to autism spectrum disorder and healthy controls.

Individuals with psychotic disorders often lead sedentary lives, heightening the risk of developing forward head posture. Forward head posture affects upper cervical vertebrae, raising the likelihood of daily discomforts like skeletal misalignment, neck pain, and reduced cardiorespiratory fitness. Improving cardiorespiratory fitness in psychotic disorders is relevant, given its proven benefits in enhancing physical and mental health. This study investigates forward head posture by measuring craniovertebral angles in psychotic disorders and the relationship with reduced cardiorespiratory fitness. To determine whether forward head posture is specific to psychotic disorders, we also included individuals with autism spectrum disorder and healthy controls. Among 85 participants (32 psychotic disorders, 26 autism spectrum disorder, 27 healthy controls), photogrammetric quantification revealed a significantly lower mean craniocervical angle in psychotic disorders compared to autism spectrum disorder (p = < 0.02) and the healthy control group (p = < 0.01). Reduced craniovertebral angle is related to diminished cardiorespiratory fitness in psychosis (R2 = 0.45, p = < 0.01) but not in other control groups. This study found reduced craniovertebral angles, indicating forward head posture in psychotic disorders. Moreover, this relates to diminished cardiorespiratory fitness. Further research is needed to examine the underlying causes and to investigate whether this can be reversed through physical therapy.

Characteristics of head and neck alignment and function of deep cervical flexor muscles in patients with nonspecific neck pain.

OBJECTIVES: The objectives were to compare forward head posture (FHP) in natural and corrected head postures between patients with nonspecific neck pain (NSNP) and controls and to clarify the relationship between natural and corrected head posture angle differences and deep cervical flexor function. This study aimed to provide useful evidence for postural assessment and treatment in patients with NSNP. METHODS: In this cross-sectional study, 19 patients with NSNP reporting a pain score of 3-7 for at least 3 months and 19 participants with no neck pain within the previous 12 months were recruited. To evaluate FHP, the cranial rotation and vertical angles were measured using lateral head and neck photographs. The craniocervical flexion test was used to evaluate deep cervical flexor activation and endurance. We evaluated the head and neck alignment in natural and corrected head postures and the relationship between the degree of change and deep cervical flexor function. RESULTS: FHP in the natural head posture did not differ between groups. In the corrected head posture, FHP was significantly smaller in the NSNP group than in the control group. In the NSNP group, the cranial rotation and vertical angles were significantly different between the natural and corrected head postures, and the angle difference correlated significantly with deep cervical flexor function. CONCLUSIONS: Patients with NSNP show hypercorrection in the corrected head posture, which may be correlated with deep cervical flexor dysfunction. Further investigation into the causal relationship between hypercorrection, deep neck flexor dysfunction, and neck pain is required.

Full-body kinematics and head stabilisation strategies during walking in patients with chronic unilateral and bilateral vestibulopathy.

Chronic imbalance is a frequent and limiting symptom of patients with chronic unilateral and bilateral vestibulopathy. A full-body kinematic analysis of the movement of patients with vestibulopathy would provide a better understanding of the impact of the pathology on dynamic tasks such as walking. Therefore, this study aimed to investigate the global body movement during walking, its variability (assessed with the GaitSD), and the strategies to stabilise the head (assessed with the head Anchoring Index). The full-body motion capture data of 10 patients with bilateral vestibulopathy (BV), 10 patients with unilateral vestibulopathy (UV), and 10 healthy subjects (HS) walking at several speeds (slow, comfortable, and fast) were analysed in this prospective cohort study. We observed only a few significant differences between groups in parts of the gait cycle (shoulder abduction-adduction, pelvis rotation, and hip flexion-extension) during the analysis of kinematic curves. Only BV patients had significantly higher gait variability (GaitSD) for all three walking speeds. Head stabilisation strategies depended on the plan of motion and walking speed condition, but BV and UV patients tended to stabilise their head in relation to the trunk and HS tended to stabilise their head in space. These results suggest that GaitSD could be a relevant biomarker of chronic instability in BV and that the head Anchoring Index tends to confirm clinical observations of abnormal head-trunk dynamics in patients with vestibulopathy while walking.

Can symptoms or signs of cervical dystonia occur without abnormal movements of the head or neck?

INTRODUCTION: Cervical dystonia is defined by excessive contraction of muscles that produce abnormal postures and movements of the head, neck, and sometimes the shoulders. Many affected individuals also have pain, local muscle hypertrophy, and/or abnormally increased EMG activity. However, abnormal movements are considered the defining feature. CASES: Three cases are described suggesting that some features of cervical dystonia may occur without abnormal movements. In these cases, the only clinical features are pain, local muscle hypertrophy, or abnormal EMG activity. These features may occur years before abnormal movements emerge, or they may occur coincidentally with dystonia affecting regions other than the neck. In some cases, some features associated with cervical dystonia may occur without any obvious abnormal movements. CONCLUSIONS: Some symptoms of cervical dystonia may occur without abnormal movements of the head or neck. The purpose of this report is not to question current diagnostic criteria for cervical dystonia, but to call attention to a phenomenon that deserves further attention. Such cases may be considered to have a pro-dromal form of cervical dystonia or a formes fruste of cervical dystonia. Whatever diagnostic label is applied, the phenomenon is important to recognize, because symptoms may be readily alleviated with botulinum toxin.

Head Kinematics and Injury Metrics for Laboratory Hockey-Relevant Head Impact Experiments.

Investigating head responses during hockey-related blunt impacts and hence understanding how to mitigate brain injury risk from such impacts still needs more exploration. This study used the recently developed hockey helmet testing methodology, known as the Hockey Summation of Tests for the Analysis of Risk (Hockey STAR), to collect 672 laboratory helmeted impacts. Brain strains were then calculated from the according 672 simulations using the detailed Global Human Body Models Consortium (GHBMC) finite element head model. Experimentally measured head kinematics and brain strains were used to calculate head/brain injury metrics including peak linear acceleration, peak rotational acceleration, peak rotational velocity, Gadd Severity Index (GSI), Head Injury Criteria (HIC15), Generalized Acceleration Model for Brain Injury Threshold (GAMBIT), Brain Injury Criteria (BrIC), Universal Brain Injury Criterion (UBrIC), Diffuse Axonal Multi-Axis General Equation (DAMAGE), average maximum principal strain (MPS) and cumulative strain damage measure (CSDM). Correlation analysis of kinematics-based and strain-based metrics highlighted the importance of rotational velocity. Injury metrics that use rotational velocity correlated highly to average MPS and CSDM with UBrIC yielding the strongest correlation. In summary, a comprehensive analysis for kinematics-based and strain-based injury metrics was conducted through a hybrid experimental (672 impacts) and computational (672 simulations) approach. The results can provide references for adopting brain injury metrics when using the Hockey STAR approach and guide ice hockey helmet designs that help reduce brain injury risks.

Vestibulocollic and Cervicocollic Muscle Reflexes in a Finite Element Neck Model During Multidirectional Impacts.

Active neck musculature plays an important role in the response of the head and neck during impact and can affect the risk of injury. Finite element Human Body Models (HBM) have been proposed with open and closed-loop controllers for activation of muscle forces; however, controllers are often calibrated to specific experimental loading cases, without considering the intrinsic role of physiologic muscle reflex mechanisms under different loading conditions. This study aimed to develop a single closed-loop controller for neck muscle activation in a contemporary male HBM based on known reflex mechanisms and assess how this approach compared to current open-loop controllers across a range of impact directions and severities. Controller parameters were optimized using volunteer data and independently assessed across twelve impact conditions. The kinematics from the closed-loop controller simulations showed good average CORA rating to the experimental data (0.699) for the impacts following the ISO/TR9790 standard. Compared to previously optimized open-loop activation strategy, the average difference was less than 9%. The incorporation of the reflex mechanisms using a closed-loop controller can provide robust performance for a range of impact directions and severities, which is critical to improving HBM response under a larger spectrum of automotive impact simulations.

The comparison of two corrective exercise approaches for hyperkyphosis and forward head posture: A quasi-experimental study.

BACKGROUND: Hyperkyphosis (HKP) and forward head posture (FHP) occur due to prolonged poor postures and repetitive activities. OBJECTIVE: The present study aimed to compare the effects of the National Academy of Sports Medicine (NASM) and Sahrmann corrective exercises on HKP and FHP correction. METHODS: This quasi-experimental study was conducted on 30 subjects with HKP and FHP, who were randomly assigned to the NASM (n= 15) and Sahrmann groups (n= 15). The ImageJ software and a spinal mouse device were used to measure FHP and HKP deformities, and neck and shoulder muscle strength, range of motion (ROM), and pulmonary function were assessed as the secondary outcomes before and after the eight-week intervention. RESULTS: FHP improved more significantly in the Sahrmann group compared to the NASM group (P< 0.05), while no significant difference was observed between the groups in HKP (P> 0.05). The improvement in the neck and shoulder muscle strength was more significant in the Sahrmann group compared to the NASM (P< 0.05), except for the neck flexors. In addition, the neck extension ROM enhanced more significantly in the Sahrmann group compared to the NASM group (P< 0.05). CONCLUSION: According to the results, the Sahrmann corrective exercises that focused on the correction of imbalanced muscle stiffness had more significant effects on the correction of FHP, neck and shoulder muscle strength and neck extension ROM.

A meta-analysis and systematic review of changes in joint position sense and static standing balance in patients with whiplash-associated disorder.

OBJECTIVE: To synthesise and analyse the current evidence regarding changes in joint position sense (JPS) and standing balance in people with whiplash-associated disorder (WAD) taking the presence or absence of dizziness into account. DATA SOURCES: PubMed, CINAHL Plus, Web of Science, Embase, MEDLINE and APA PsycINFO were searched by two independent reviewers from inception until August 2020 and reference lists of all included studies were also reviewed. STUDY SELECTION: Only cross-sectional studies that measured JPS and/or standing balance between people with WAD vs. healthy controls (HC) or people with WAD complaining of dizziness (WADD) vs. those not complaining of dizziness (WADND) were selected. DATA EXTRACTION: Relevant data were extracted using specific checklists and quality assessment was performed using Downs and Black Scale (modified version). DATA SYNTHESIS: Twenty-six studies were included. For JPS, data were synthesized for absolute error in the primary plane of movement for separate movement directions. For standing balance, data were synthesized for traditional time- and frequency domain sway parameters considering the conditions of eyes open (EO) and eyes closed (EC) separately. For meta-analysis, reduced JPS was observed in people with WAD compared to HC when the head was repositioned to a neutral head position (NHP) from rotation (standardised mean difference [SMD] = 0.43 [95%: 0.24-0.62]) and extension (0.33 [95%CI: 0.08-0.58]) or when the head was moved toward 50° rotation from a NHP (0.50 [0.05-0.96]). Similarly, people with WADD had reduced JPS compared to people with WADND when the head was repositioned to a NHP from rotation (0.52 [0.22-0.82]). Larger sway velocity and amplitude was found in people with WAD compared to HC for both EO (0.62 [0.37-0.88] and 0.78 [0.56-0.99], respectively) and EC (0.69 [0.46-0.91] and 0.80 [0.58-1.02]) conditions. CONCLUSION: The observed changes of JPS and standing balance confirms deficits in sensorimotor control in people with WAD and especially in those with dizziness.

Odontogenic Head and Neck Region Infections Requiring Hospitalization: An 18-Month Retrospective Analysis.

The aim of this study was to comprehensively review our experience with odontogenic infections in the head and neck region requiring treatment at a national referral center. We retrospectively reviewed 85 patients treated at the Chair and Clinic of Maxillofacial Surgery of the University Hospital in Wroclaw between January 2018 and June 2019. We excluded patients with nonondontogenic infections or other than purulent clinical forms of dentivitis in the head and neck region. Several demographic, clinicopathological, and treatment variables were assessed. The majority of patients were men who were referred for inpatient treatment by a dentist or family doctor, presented to the Hospital Emergency Ward (SOR) by themselves, or transported to the SOR by paramedics SOR from their home or another hospital. All patients were treated in accordance with the current guidelines for head and neck region odontogenic infections. An incision was made and the abscess was drained. The odontogenic cause was removed followed by the collection of tissue for microbiological examination. The course of infection was monitored by means of laboratory parameters such as leukocyte counts and c-reactive protein levels. Odontogenic infections in the head and neck region are a persistent and common problem. Rapid, accurate diagnosis and treatment minimizes the risk of life-threatening complications, shortens the hospitalization period, and lowers treatment costs.

Control of Linear Head and Trunk Acceleration During Gait After Unilateral Vestibular Deficits.

OBJECTIVE: To use clinically available inertial measurement units to quantify the control of linear accelerations at the head and trunk during gait in different sensory conditions in individuals with unilateral vestibular loss. DESIGN: Observational study. SETTING: Outpatient research laboratory. PARTICIPANTS: Individuals (n=13; mean age, 47.6±13.7y; 69% women) 6 weeks after vestibular schwannoma resection surgery and vestibular healthy participants (n=16; mean age, 29.7±5.9y; 56% women). INTERVENTION: Not applicable. MAIN OUTCOME MEASURES: Walking speed normalized, root mean square values of cranial-caudal, medial-lateral, and anterior-posterior directed linear accelerations at the head and the trunk while walking in 2 visual sensory conditions (eyes open and eyes closed). RESULTS: Linear mixed models for each root mean square value were fit on the effects of group, condition, and group by condition. The group by condition effect was used to examine the primary hypothesis that individuals with vestibular loss would experience greater change in triplanar root mean square values at the head and trunk from the eyes open to eyes closed condition compared with the vestibular healthy group. The group by condition effect was found to be significant at the head in the cranial-caudal (ß=0.39; P=.002), medial-lateral (ß=0.41; P<.001), and anterior-posterior (ß=0.43; P<.001) directions. The group by condition effect was also significant in the cranial-caudal (ß=0.39; P=.002), medial-lateral (ß=0.39; P<.001), and anterior-posterior (ß=0.23; P=.002) directions at the trunk. CONCLUSIONS: Participants who underwent vestibular schwannoma resection were more impaired in their ability to control accelerations at the head and trunk without visual sensory information than vestibular healthy participants. These impairments were detectable using clinically available inertial measurement units.

A Review of On-Field Investigations into the Biomechanics of Concussion in Football and Translation to Head Injury Mitigation Strategies.

This review paper summarizes the scientific advancements in the field of concussion biomechanics in American football throughout the past five decades. The focus is on-field biomechanical data collection, and the translation of that data to injury metrics and helmet evaluation. On-field data has been collected with video analysis for laboratory reconstructions or wearable head impact sensors. Concussion biomechanics have been studied across all levels of play, from youth to professional, which has allowed for comparison of head impact exposure and injury tolerance between different age groups. In general, head impact exposure and injury tolerance increase with increasing age. Average values for concussive head impact kinematics are lower for youth players in both linear and rotational acceleration. Head impact data from concussive and non-concussive events have been used to develop injury metrics and risk functions for use in protective equipment evaluation. These risk functions have been used to evaluate helmet performance for each level of play, showing substantial differences in the ability of different helmet models to reduce concussion risk. New advances in head impact sensor technology allow for biomechanical measurements in helmeted and non-helmeted sports for a more complete understanding of concussion tolerance in different demographics. These sensors along with advances in finite element modeling will lead to a better understanding of the mechanisms of injury and human tolerance to head impact.

High Energy Side and Rear American Football Head Impacts Cause Obvious Performance Decrement on Video.

The objective of this study was to compare head impact data acquired with an impact monitoring mouthguard (IMM) to the video-observed behavior of athletes' post-collision relative to their pre-collision behaviors. A total of n = 83 college and high school American football players wore the IMM and were video-recorded over 260 athlete-exposures. Ex-athletes and clinicians reviewed the video in a two-step process and categorized abnormal post-collision behaviors according to previously published Obvious Performance Decrement (OPD) definitions. Engineers qualitatively reviewed datasets to check head impact and non-head impact signal frequency and magnitude. The ex-athlete reviewers identified 2305 head impacts and 16 potential OPD impacts, 13 of which were separately categorized as Likely-OPD impacts by the clinical reviewers. All 13 Likely-OPD impacts were in the top 1% of impacts measured by the IMM (ranges 40-100 g, 3.3-7.0 m/s and 35-118 J) and 12 of the 13 impacts (92%) were to the side or rear of the head. These findings require confirmation in a larger data set before proposing any type of OPD impact magnitude or direction threshold exists. However, OPD cases in this study compare favorably with previously published impact monitoring studies in high school and college American football players that looked for OPD signs, impact magnitude and direction. Our OPD findings also compare well with NFL reconstruction studies for ranges of concussion and sub-concussive impact magnitudes in side/rear collisions, as well as prior theory, analytical models and empirical research that suggest a directional sensitivity to brain injury exists for single high-energy impacts.

Laboratory Reconstructions of Concussive Helmet-to-Helmet Impacts in the National Football League.

Seventeen concussive helmet-to-helmet impacts occurring in National Football League (NFL) games were analyzed using video footage and reconstructed by launching helmeted crash test dummies into each other in a laboratory. Helmet motion on-field and in the laboratory was tracked in 3D before, during, and after impact in multiple high frame rate video views. Multiple (3-10) tests were conducted for each of the 17 concussive cases (100 tests total) with slight variations in input conditions. Repeatability was assessed by duplicating one or two tests per case. The accuracy of the input conditions in each reconstruction was assessed based on how well the closing velocity, impact locations, and the path eccentricity of the dummy heads matched the video analysis. The accuracy of the reconstruction output was assessed based on how well the changes in helmet velocity (translational and rotational) from the impact matched the video analysis. The average absolute error in helmet velocity changes was 24% in the first test, 20% in the tests with the most accurate input configuration, and 14% in the tests with minimal error. Coefficients of variation in 22 repeated test conditions (1-2 per case) averaged 3% for closing velocity, 7% for helmet velocity changes, and 8% for peak head accelerations. Iterative testing was helpful in reducing error. A combination of sophisticated video analysis, articulated physical surrogates, and iterative testing was required to reduce the error to within half of the effect size of concussion.

Effects of Deep Cervical Flexor Training on Forward Head Posture, Neck Pain, and Functional Status in Adolescents Using Computer Regularly.

In contemporary societies, computer use by children is a necessity and thus highly prevalent. Using computers for long hours is related to a higher risk of computer-related muscular disorders like forward head posture (FHP) and neck pain (NP). Deep cervical flexor (DCF) muscles are important head-on-neck posture stabilizers; thus, their training may lead to an improvement in FHP and NP. The aim of this study was to determine if 4 weeks of DCF training is effective in alleviating NP, improving FHP, and functional status in adolescent children using computers regularly, a pretest-posttest experimental group design was used. Subjects were randomly assigned into the experimental group (receiving DCF training and postural education) and the control group (receiving postural education only). 30 subjects with a mean age of 15.7 ± 1.725 years with NP and FHP using computers regularly participated in the study. Dependent variables were measured on day 1 (at baseline) and after 4 weeks of training. Photographic analysis was used for measuring FHP, visual analog scale for NP intensity, and neck disability index for functional status. Data analysis showed that in both groups, no significant improvement occurred in FHP. In both groups, there was a significant improvement in functional status and NP. There was no significant difference between both groups for FHP and NP. There was a significant improvement in functional status in the experimental group in comparison to the control group. Four weeks of DCF training does not cause a significant improvement in FHP in 13 to 18 years old adolescent children using computers regularly.

Position-Specific Circumstances of Concussions in the NFL: Toward the Development of Position-Specific Helmets.

Consideration of position-specific features of the NFL concussion environment could enable improved risk mitigation through the design of position-specific helmets to improve self-protection as well as protection for the other player with whom the contact occurs. The purpose of this paper is to quantify position-specific features of scenarios resulting in concussions to NFL players, and the players they contact, by reviewing all game footage (broadcast and non-broadcast) over 4 seasons. Position-specific features were documented for 647 concussions in which a primary exposure could be visualized, including impact source, helmet impact location, activity, and the other player with whom the contact occurred. Findings include the over-representation of helmet-to-ground impacts to the rear of the quarterback's helmet, the high frequency of impacts to the side (upper) location of both concussed players and the players they contacted regardless of position, and distinct differences in the circumstances of concussions to cornerbacks and safeties. The study shows that some features of concussion scenarios are common to all positions, but several position-specific features exist and can inform the design of position-specific helmets for NFL players.

On-Field Performance of an Instrumented Mouthguard for Detecting Head Impacts in American Football.

Wearable sensors that accurately record head impacts experienced by athletes during play can enable a wide range of potential applications including equipment improvements, player education, and rule changes. One challenge for wearable systems is their ability to discriminate head impacts from recorded spurious signals. This study describes the development and evaluation of a head impact detection system consisting of a mouthguard sensor and machine learning model for distinguishing head impacts from spurious events in football games. Twenty-one collegiate football athletes participating in 11 games during the 2018 and 2019 seasons wore a custom-fit mouthguard instrumented with linear and angular accelerometers to collect kinematic data. Video was reviewed to classify sensor events, collected from instrumented players that sustained head impacts, as head impacts or spurious events. Data from 2018 games were used to train the ML model to classify head impacts using kinematic data features (127 head impacts; 305 non-head impacts). Performance of the mouthguard sensor and ML model were evaluated using an independent test dataset of 3 games from 2019 (58 head impacts; 74 non-head impacts). Based on the test dataset results, the mouthguard sensor alone detected 81.6% of video-confirmed head impacts while the ML classifier provided 98.3% precision and 100% recall, resulting in an overall head impact detection system that achieved 98.3% precision and 81.6% recall.

A Two-Phased Approach to Quantifying Head Impact Sensor Accuracy: In-Laboratory and On-Field Assessments.

Measuring head impacts in sports can further our understanding of brain injury biomechanics and, hopefully, advance concussion diagnostics and prevention. Although there are many head impact sensors available, skepticism on their utility exists over concerns related to measurement error. Previous studies report mixed reliability in head impact sensor measurements, but there is no uniform approach to assessing accuracy, making comparisons between sensors and studies difficult. The objective of this paper is to introduce a two-phased approach to evaluating head impact sensor accuracy. The first phase consists of in-lab impact testing on a dummy headform at varying impact severities under loading conditions representative of each sensor's intended use. We quantify in-lab accuracy by calculating the concordance correlation coefficient (CCC) between a sensor's kinematic measurements and headform reference measurements. For sensors that performed reasonably well in the lab (CCC ≥ 0.80), we completed a second phase of evaluation on-field. Through video validation of impacts measured by sensors on athletes, we classified each sensor measurement as either true-positive and false-positive impact events and computed positive predictive value (PPV) to summarize real-world accuracy. Eight sensors were tested in phase one, but only four sensors were assessed in phase two. Sensor accuracy varied greatly. CCC from phase one ranged from 0.13 to 0.97, with an average value of 0.72. Overall, the four devices that were implemented on-field had PPV that ranged from 16.3 to 91.2%, with an average value of 60.8%. Performance in-lab was not always indicative of the device's performance on-field. The methods proposed in this paper aim to establish a comprehensive approach to the evaluation of sensors so that users can better interpret data collected from athletes.

Characterization of Concussive Events in Professional American Football Using Videogrammetry.

Sports concussions offer a unique opportunity to study head kinematics associated with mild traumatic brain injury. In this study, a model-based image matching (MBIM) approach was employed to analyze video footage of 57 concussions which occurred in National Football League (NFL) games. By utilizing at least two camera views, higher frame rate footage (> 60 images s-1), and laser scans of the field and helmets involved in each case, it was possible to calculate the change in velocity of the helmet during impact in six degrees of freedom. The average impact velocity for these concussive events was 8.9 ± 2.0 m s-1. The average changes in translational and rotational velocity for the concussed players' helmets were 6.6 ± 2.1 m s-1 and 29 ± 13 rad s-1, respectively. The average change in translational velocity was higher for helmet-to-ground (n = 16) impacts compared to helmet-to-helmet (n = 30) or helmet-to-shoulder (n = 11) events (p < 0.001), while helmet-to-shoulder impacts had a smaller change in rotational velocity compared to the other impact sources (p < 0.001). By quantifying the impact velocities and locations associated with concussive impacts in professional American football, this study provides information that may be used to improve upon current helmet testing methodologies.