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1.
Auris Nasus Larynx ; 51(4): 738-746, 2024 Aug.
Article de Anglais | MEDLINE | ID: mdl-38850719

RÉSUMÉ

OBJECTIVE: The present study aimed to observe and analyze the ocular movements induced by Coriolis stimulation (eccentric pitch while rotating: PWR) that induces Coriolis forces on the vestibular apparatus of healthy human individuals. METHODS: A total of 31 healthy subjects participated in the study. Eccentric PWR was performed on 27 subjects, by pitching the participants' heads forward and backward at an angle of 30° each on an axis parallel and 7 cm below inter-aural axis, at a frequency of 0.5 Hz while on a chair rotating at a constant angular velocity of 97.2°/s on the earth-vertical axis. Ocular movements during stimulation were recorded using three-dimensional video-oculography. As a subsidiary analysis, 0.5 Hz head roll tilt was used as another stimulus that also induced torsional ocular movements. The forces induced on the vestibular apparatus, and phases of ocular torsion against the stimulus were calculated from the observed data. RESULTS: In the Coriolis stimulation during rightward yaw rotation, a rightward ocular torsion of 4.8° on average, was observed when the head pitched forward, and the direction of ocular torsion reversed when the head pitched backward. During leftward yaw rotation, these relationships were reversed with an average amplitude of 4.7° The phase of ocular torsion preceded that of Coriolis force by 0.2 s during rightward rotation and 0.14 s during leftward rotation. There were no significant differences in amplitude or phase between the directions of rotation. The phase lead of 0.5 Hz roll-tilt was significantly smaller than that of Coriolis stimulation (p < 0.01). CONCLUSION: Coriolis stimulation induced a specific pattern of ocular torsion, where its direction and phase suggested that the mechanism likely involved both the otolith and semicircular canals. Further studies may provide a clue to the magnitude of the otolith and semicircular canal contributions.


Sujet(s)
Mouvements oculaires , Humains , Mâle , Adulte , Femelle , Mouvements oculaires/physiologie , Jeune adulte , Force de Coriolis , Rotation , Volontaires sains , Mouvements de la tête/physiologie
2.
Adv Anat Embryol Cell Biol ; 236: 151-155, 2023.
Article de Anglais | MEDLINE | ID: mdl-37955775

RÉSUMÉ

The ear serves two vital functions of hearing and maintaining balance. It achieves these roles within three major compartments: the outer, the middle, and the inner ear. Embryological development of the ear and its associated structures have been studied in some animal models. Yet, the role of skeletal muscle in ear development and its related structures is largely unknown. Research suggests the outer ear and parts of the inner ear may require skeletal muscle for normal embryogenesis. Here, we describe the role of skeletal muscle in the development of the ear and its associated structures. Moreover, we report the possible consequences of defect in the skeletal muscle of the ear and the clinical correlates of such consequences.


Sujet(s)
Oreille interne , Muscles squelettiques , Animaux , Accélération , Oreille externe , Développement embryonnaire
3.
J Sports Sci ; 41(7): 631-645, 2023 Jun.
Article de Anglais | MEDLINE | ID: mdl-37393593

RÉSUMÉ

This study aimed to quantitatively investigate and report the biomechanical characteristics of concussive and sub-concussive impacts in youth sports. A systematic search was conducted in September 2022 to identify biomechanical impact studies in athletes ≤18 years of age. Twenty-six studies met the inclusion criteria for quantitative synthesis and analysis. DerSimonian Laird random effects model was used to pool data across the included studies. The pooled estimate of mean peak linear and rotational acceleration of concussive impacts in male youth athletes was 85.56 g (95% CI 69.34-101.79) and 4505.58 rad/s2 (95% CI 2870.28-6140.98), respectively. The pooled estimate of mean peak linear and rotational acceleration of sub-concussive impacts in youth athletes was 22.89 g (95% CI 20.69-25.08) and 1290.13 rad/s2 (95% CI 1050.71-1529.55), respectively. A male vs female analysis in sub-concussive impacts revealed higher linear and rotational acceleration in males and females, respectively. This is the first study to report on impact data in both sexes of youth athletes. Disparity in kinematic impact values suggests future research should aim for standardised measures to reduce heterogeneity in data. Despite this, the data reveals notable impact data that youth athletes are exposed to, suggesting modifications may be required to reduce long-term neurological risks.


Sujet(s)
Traumatismes sportifs , Commotion de l'encéphale , Football américain , Sports pour les jeunes , Adolescent , Humains , Mâle , Femelle , Athlètes , Accélération , Phénomènes biomécaniques
4.
Brain Commun ; 5(2): fcad062, 2023.
Article de Anglais | MEDLINE | ID: mdl-37006333

RÉSUMÉ

A mild traumatic brain injury is a neurological disturbance of transient or/and chronic nature after a direct blow of the head/neck or exposure of the body to impulsive biomechanical forces, indirectly affecting the brain. The neuropathological events leading to the clinical signs, symptoms and functional disturbances are still elusive due to a lack of sensitive brain-screening tools. Animal models offer the potential to study neural pathomechanisms in close detail. We recently proposed a non-invasive protocol for inducing concussion-like symptoms in larval zebrafish via exposure to rapid linearly accelerating-decelerating body motion. By mean of auditory 'startle reflex habituation' assessments-an established neurophysiological health index-we probed acute and chronic effects that mirror human concussion patterns. This study aimed at expanding our previous work by assessing the ensuing effects with visual-as opposed to auditory-'startle reflex habituation' quantifications, by using the same methodology. We observed that immediately after impact exposure, the fish showed impaired sensory reactivity and smaller decay constant, possibly mirroring acute signs of confusion or loss of consciousness in humans. By 30-min post-injury, the fish display temporary signs of visual hypersensitivity, manifested as increased visuomotor reactivity and a relatively enlarged decay constant, putatively reflecting human post-concussive sign of visual hypersensitivity. In the following 5-24 h, the exposed fish progressively develop chronic signs of CNS dysfunction, in the form of low startle responsivity. However, the preserved decay constant suggests that neuroplastic changes may occur to restore CNS functioning after undergoing the 'concussive procedure'. The observed findings expand our previous work providing further behavioural evidence for the model. Limitations that still require addressment are discussed, advancing further behavioural and microscopic analyses that would be necessary for the validation of the model in its putative relatability with human concussion.

5.
Sensors (Basel) ; 22(15)2022 Jul 26.
Article de Anglais | MEDLINE | ID: mdl-35898094

RÉSUMÉ

Traumatic Brain Injuries (TBIs) are one of the most frequent and severe outcomes of a Powered Two-Wheeler (PTW) crash. Early diagnosis and treatment can greatly reduce permanent consequences. Despite the fact that devices to track head kinematics have been developed for sports applications, they all have limitations, which hamper their use in everyday road applications. In this study, a new technical solution based on accelerometers integrated in a motorcycle helmet is presented, and the related methodology to estimate linear and rotational acceleration of the head with deep Artificial Neural Networks (dANNs) is developed. A finite element model of helmet coupled with a Hybrid III head model was used to generate data needed for the neural network training. Input data to the dANN model were time signals of (virtual) accelerometers placed on the inner surface of the helmet shell, while the output data were the components of linear and rotational head accelerations. The network was capable of estimating, with good accuracy, time patterns of the acceleration components in all impact conditions that require medical treatment. The correlation between the reference and estimated values was high for all parameters and for both linear and rotational acceleration, with coefficients of determination (R2) ranging from 0.91 to 0.97.


Sujet(s)
Accidents de la route , Dispositifs de protection de la tête , Accélération , Phénomènes biomécaniques , Tête , Motocyclettes ,
6.
Article de Anglais | MEDLINE | ID: mdl-35564889

RÉSUMÉ

Epidemiological studies of the neurological health of former professional soccer players are being undertaken to identify whether heading the ball is a risk factor for disease or premature death. A quantitative estimate of exposure to repeated sub-concussive head impacts would provide an opportunity to investigate possible exposure-response relationships. However, it is unclear how to formulate an appropriate exposure metric within the context of epidemiological studies. We have carried out a systematic review of the scientific literature to identify the factors that determine the magnitude of head impact acceleration during experiments and from observations during playing or training for soccer, up to the end of November 2021. Data were extracted from 33 experimental and 27 observational studies from male and female amateur players including both adults and children. There was a high correlation between peak linear and angular accelerations in the observational studies (p < 0.001) although the correlation was lower for the experimental data. We chose to rely on an analysis of maximum or peak linear acceleration for this review. Differences in measurement methodology were identified as important determinants of measured acceleration, and we concluded that only data from accelerometers fixed to the head provided reliable information about the magnitude of head acceleration from soccer-related impacts. Exposures differed between men and women and between children and adults, with women on average experiencing higher acceleration but less frequent impacts. Playing position appears to have some influence on the number of heading impacts but less so on the magnitude of the head acceleration. Head-to-head collisions result in high levels of exposure and thus probably risk causing a concussion. We concluded, in the absence of evidence to the contrary, that estimates of the cumulative number of heading impacts over a playing career should be used as the main exposure metric in epidemiological studies of professional players.


Sujet(s)
Commotion de l'encéphale , Football , Accélération , Adulte , Athlètes , Commotion de l'encéphale/épidémiologie , Commotion de l'encéphale/étiologie , Enfant , Femelle , Tête , Humains , Mâle , Facteurs de risque , Football/physiologie
7.
Ann Biomed Eng ; 50(6): 728-739, 2022 Jun.
Article de Anglais | MEDLINE | ID: mdl-35366746

RÉSUMÉ

Accurate characterization of head kinematics following an external blow represents a fundamental aspect of traumatic brain injury (TBI) research. The majority of previous large animal studies have assumed an equivalent relationship between the device delivering the impulsive load and subsequent head kinematics rather than performing direct measurement (sensors or videography). The current study therefore examined factors affecting device/head coupling kinematics in an acceleration TBI model. Experiment 1 indicated ~ 50% reduction in peak angular velocity for swine head relative to the device, with an approximate doubling in temporal duration. The peak angular velocity for the head was not significantly altered by variations in restraint device (straps vs. cables), animal positioning or body mass. In Experiment 2, reducing the impulsive load by 32% resulted in only a 14% reduction in angular velocity of the head (approximately 69% head/device coupling ratio), with more pronounced differences qualitatively observed for angular momentum. A temporal delay was identified in initial device/head coupling, potentially a result of soft tissue deformation. Finally, similar head kinematics were obtained regardless of mounting the sensor directly to the skull or through the scalp (Experiment 3). Current findings highlight the importance of direct measurement of head kinematics for future studies.


Sujet(s)
Accélération , Lésions traumatiques de l'encéphale , Animaux , Phénomènes biomécaniques , Tête , Suidae
8.
J Appl Biomech ; 38(1): 47-57, 2022 02 01.
Article de Anglais | MEDLINE | ID: mdl-35045388

RÉSUMÉ

This study quantified head impact exposures for Canadian university football players over their varsity career. Participants included 63 players from one team that participated in a minimum of 3 seasons between 2013 and 2018. A total of 127,192 head impacts were recorded from 258 practices and 65 games. The mean (SD) number of career impacts across all positions was 2023.1 (1296.4), with an average of 37.1 (20.3) impacts per game and 7.4 (4.4) impacts per practice. The number of head impacts that players experienced during their careers increased proportionally to the number of athletic exposures (P < .001, r = .57). Linebackers and defensive and offensive linemen experienced significantly more head impacts than defensive backs, quarterbacks, and wide receivers (P ≤ .014). Seniority did not significantly affect the number of head impacts a player experienced. Mean linear acceleration increased with years of seniority within defensive backs and offensive linemen (P ≤ .01). Rotational velocity increased with years of seniority within defensive backs, defensive and offensive linemen, running backs, and wide receivers (P < .05). These data characterize career metrics of head impact exposure for Canadian university football players and provide insights to reduce head impacts through rule modifications and contact regulations.


Sujet(s)
Commotion de l'encéphale , Football américain , Course à pied , Accélération , Canada , Humains , Universités
9.
Ann Biomed Eng ; 50(11): 1546-1564, 2022 Nov.
Article de Anglais | MEDLINE | ID: mdl-35059915

RÉSUMÉ

Rugby union is a popular sport played across the world. The physical contact inherent in the game means that players are at increased risk of concussive injury. In 2019, World Rugby created a new category of permitted headgear under Law 4 as a medical device. This established a pathway for headgear designed to reduce peak accelerations to be worn in matches. Investigations of the potential of soft-shelled protective headgear to reduce head impact accelerations have been mostly limited to the analysis of linear kinematics. However rotational head impact accelerations have long been implicated as far more injurious. The aim of this study, therefore, was to assess the linear and rotational acceleration reduction brought about by soft-shelled rugby headgear. A Hybrid III headform and neck were dropped onto a modular elastomer programmer impact surface, impacting at four different velocities (1.7-3.4 m/s) in five different impact orientations. Impact surface angles were 0°, 30°, and 45°. Peak linear and rotational accelerations, PLA and PRA respectively, were recorded. All headgear significantly reduced PLAs and PRAs when compared to a no headgear scenario. The new generation, headgear reduced all measures significantly more than the older generation of headgear. Impact locations offset from the center of mass of the headform resulted in the highest PRAs measured. As the impact surface angle increased, both PLAs and PRAs decreased. The study demonstrated that headgear tested lowered PLAs by up to 50%, and PRAs by up to 60% compared to the bare headform. Our data suggest that new generation headgear could make a difference on the field in reducing injurious impact accelerations in a collision.


Sujet(s)
Rugby , Sports , Dispositifs de protection de la tête , Accélération , Phénomènes biomécaniques
10.
Orthop J Sports Med ; 9(12): 23259671211059815, 2021 Dec.
Article de Anglais | MEDLINE | ID: mdl-34901294

RÉSUMÉ

BACKGROUND: The accumulation of subconcussive impacts has been implicated in permanent neurological impairment. A gap in understanding the relationship between head impacts and neurological function is the lack of precise characterization and quantification of forces that individuals experience during sports training and competition. PURPOSE: To characterize impact exposure during training and competition among male and female athletes participating in boxing and mixed martial arts (MMA) via an instrumented custom-fit Impact Monitoring Mouthguard (IMM). STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: Twenty-three athletes (n = 4 women) were provided a custom-fit IMM. The IMM monitored impacts during sparring and competition. All training and competition sessions were videotaped. Video and IMM data were synchronized for post hoc data verification of true positives and substantiation of impact location. IMM data were collected from boxing and MMA athletes at a collaborating site. For each true-positive impact, peak linear acceleration and peak angular acceleration were calculated. Wilcoxon rank sum tests were used to evaluate potential differences in sport, activity type, and sex with respect to each outcome. Differences in impact location were assessed via Kruskal-Wallis tests. RESULTS: IMM data were collected from 53 amateur training sessions and 6 competitions (session range, 5-20 minutes). A total of 896 head impacts (men, n = 786; women, n = 110) were identified using IMM data and video verification: 827 in practice and 69 during competition. MMA and boxers experienced a comparable number of impacts per practice session or competition. In general, MMA impacts produced significantly higher peak angular acceleration than did boxing impacts (P < .001) and were more varied in impact location on the head during competitions. In terms of sex, men experienced a greater number of impacts than women per practice session. However, there was no significant difference between men and women in terms of impact magnitude. CONCLUSION: Characteristic profiles of head impact exposure differed between boxing and MMA athletes; however, the impact magnitudes were not significantly different for male and female athletes.

11.
Neurotrauma Rep ; 2(1): 354-362, 2021.
Article de Anglais | MEDLINE | ID: mdl-34901935

RÉSUMÉ

Head impacts in soccer have been associated with both short- and long-term neurological consequences. Youth players' brains are especially vulnerable given that their brains are still developing, and females are at an increased risk of traumatic brain injury (TBI) compared to males. Approximately 90% of head impacts in soccer occur from purposeful heading. Accordingly, this study assessed the relationship between kinematic variables and brain strain during purposeful headers in female youth soccer players. A convenience sample of 36 youth female soccer players (13.4 [0.9] years of age) from three elite youth soccer teams wore wireless sensors to quantify head impact magnitudes during games. Purposeful heading events were categorized by game scenario (e.g., throw-in, goal kick) for 60 regular season games (20 games per team). A total of 434 purposeful headers were identified. Finite element model simulations were performed to calculate average peak maximum principal strain (APMPS) in the corpus callosum, thalamus, and brainstem on a subset of 110 representative head impacts. Rotational velocity was strongly associated with APMPS in these three regions of the brain (r = 0.83-0.87). Linear acceleration was weakly associated with APMPS (r = 0.13-0.31). Game scenario did not predict APMPS during soccer games (p > 0.05). Results demonstrated considerable APMPS in the corpus callosum (mean = 0.102) and thalamus (mean = 0.083). In addition, the results support the notion that rotational velocity is a better predictor of brain strain than linear acceleration and may be a potential indicator of changes to the brain.

12.
Ann Biomed Eng ; 49(12): 3189-3199, 2021 Dec.
Article de Anglais | MEDLINE | ID: mdl-34622314

RÉSUMÉ

Contact sports players frequently sustain head impacts, most of which are mild impacts exhibiting 10-30 g peak head center-of-gravity (CG) linear acceleration. Wearable head impact sensors are commonly used to measure exposure and typically detect impacts using a linear acceleration threshold. However, linear acceleration across the head can substantially vary during 6-degree-of-freedom motion, leading to triggering biases that depend on sensor location and impact condition. We conducted an analytical investigation with impact characteristics extracted from on-field American football and soccer data. We assumed typical mouthguard sensor locations and evaluated whether simulated multi-directional impacts would trigger recording based on per-axis or resultant acceleration thresholding. Across 1387 impact directions, a 10g peak CG linear acceleration impact would trigger at only 24.7% and 31.8% of directions based on a 10 g per-axis and resultant acceleration threshold, respectively. Anterior impact locations had lower trigger rates and even a 30 g impact would not trigger recording in some directions. Such triggering biases also varied by sensor location and linear-rotational head kinematics coupling. Our results show that linear acceleration-based impact triggering could lead to considerable bias in head impact exposure measurements. We propose a set of recommendations to consider for sensor manufacturers and researchers to mitigate this potential exposure measurement bias.


Sujet(s)
Accélérométrie/instrumentation , Football américain , Mouvements de la tête , Protecteurs buccaux , Football , Adolescent , Adulte , Phénomènes biomécaniques , Femelle , Humains , Mâle , Rotation
13.
Ann Biomed Eng ; 48(12): 2734-2750, 2020 Dec.
Article de Anglais | MEDLINE | ID: mdl-33200263

RÉSUMÉ

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.


Sujet(s)
Commotion de l'encéphale/physiopathologie , Football américain/traumatismes , Phénomènes biomécaniques , Commotion de l'encéphale/prévention et contrôle , Tête/physiopathologie , Dispositifs de protection de la tête , Humains , Technologie sans fil
14.
Proc Inst Mech Eng H ; 234(12): 1472-1483, 2020 Dec.
Article de Anglais | MEDLINE | ID: mdl-32799750

RÉSUMÉ

Concern about the consequences of head impacts in US football has motivated researchers to investigate and develop instrumentation to measure the severity of these impacts. However, the severity of head impacts in unhelmeted sports is largely unknown as miniaturised sensor technology has only recently made it possible to measure these impacts in vivo. The objective of this study was to measure the linear and angular head accelerations in impacts in mixed martial arts, and correlate these with concussive injuries. Thirteen mixed martial arts fighters were fitted with the Stanford instrumented mouthguard (MiG2.0) participated in this study. The mouthguard recorded linear acceleration and angular velocity in 6 degrees of freedom. Angular acceleration was calculated by differentiation. All events were video recorded, time stamped and reported impacts confirmed. A total of 451 verified head impacts above 10g were recorded during 19 sparring events (n = 298) and 11 competitive events (n = 153). The average resultant linear acceleration was 38.0624.3g while the average resultant angular acceleration was 256761739 rad/s2. The competitive bouts resulted in five concussions being diagnosed by a medical doctor. The average resultant acceleration (of the impact with the highest angular acceleration) in these bouts was 86.7618.7g and 756163438 rad/s2. The average maximum Head Impact Power was 20.6kW in the case of concussion and 7.15kW for the uninjured athletes. In conclusion, the study recorded novel data for sub-concussive and concussive impacts. Events that resulted in a concussion had an average maximum angular acceleration that was 24.7% higher and an average maximum Head Impact Power that was 189% higher than events where there was no injury. The findings are significant in understanding the human tolerance to short-duration, high linear and angular accelerations.


Sujet(s)
Commotion de l'encéphale , Football américain , Arts martiaux , Accélération , Phénomènes biomécaniques , Tête , Dispositifs de protection de la tête , Humains
15.
Article de Anglais | MEDLINE | ID: mdl-32258009

RÉSUMÉ

Diffuse axonal injury (DAI) is a severe form of traumatic brain injury and often induced by blunt trauma. The closed head impact acceleration (IA) model is the most widely used rodent DAI model. However, this model results in large variations of injury severity. Recently, the impact device/system was modified to improve the consistency of the impact energy, but variations of the head kinematics and subsequent brain injuries were still observed. This study was aimed to utilize a Finite Element (FE) model of a rat head/body and simulation to investigate the potential biomechanical factors influencing the impact energy transfer to the head. A detailed FE rat head model containing detailed skull and brain anatomy was developed based on the MRI, microCT and atlas data. The model consists of over 722,000 elements, of which 310,000 are in the brain. The white matter structures consisting of highly aligned axonal fibers were simulated with transversely isotropic material. The rat body was modeled to provide a realistic boundary at the spine-medulla junction. Rodent experiments including dynamic cortical deformation, brain-skull displacement, and IA kinematics were simulated to validate the FE model. The model was then applied to simulate the rat IA experiments. Parametric studies were conducted to investigate the effect of the helmet inclination angles (0°-5°) and skull stiffness (varied 20%) on the resulting head kinematics and maximum principal strain in the brain. The inclination angle of the helmet at 5° could vary head linear acceleration by 8-31%. The change in head rotational velocity was inversely related to the change in linear acceleration. Varying skull stiffness resulted in changes in head linear acceleration by 3% but with no effect on rotational velocity. The brain strain in the corpus callosum was only affected by head rotation while the strain in the brainstem was influenced by the combined head kinematics, local skull deformation, and head-neck position. Validated FE models of rat impact head injury can assist in exploring various biomechanical factors influencing the head impact response and internal brain response. Identification of these variables may help explain the variability of injury severity observed among experiments and across different labs.

16.
Curr Biol ; 29(3): 392-401.e4, 2019 02 04.
Article de Anglais | MEDLINE | ID: mdl-30686738

RÉSUMÉ

Rocking has long been known to promote sleep in infants and, more recently, also in adults, increasing NREM sleep stage N2 and enhancing EEG slow waves and spindles. Nevertheless, whether rocking also promotes sleep in other species, and what the underlying mechanisms are, has yet to be explored. In the current study, C57BL/6J mice equipped with EEG and EMG electrodes were rocked laterally during their main sleep period, i.e., the 12-h light phase. We observed that rocking affected sleep in mice with a faster optimal rate than in humans (1.0 versus 0.25 Hz). Specifically, rocking mice at 1.0 Hz increased time spent in NREM sleep through the shortening of wake episodes and accelerated sleep onset. Although rocking did not increase EEG activity in the slow-wave and spindle-frequency ranges in mice, EEG theta activity (6-10 Hz) during active wakefulness shifted toward slower frequencies. To test the hypothesis that the rocking effects are mediated through the vestibular system, we used the otoconia-deficient tilted (tlt) mouse, which cannot encode linear acceleration. Mice homozygous for the tlt mutation were insensitive to rocking at 1.0 Hz, while the sleep and EEG response of their heterozygous and wild-type littermates resembled those of C57BL/6J mice. Our findings demonstrate that rocking also promotes sleep in the mouse and that this effect requires input from functional otolithic organs of the vestibule. Our observations also demonstrate that the maximum linear acceleration applied, and not the rocking rate per se, is key in mediating the effects of rocking on sleep.


Sujet(s)
Encéphale/physiologie , Déplacement , Sommeil/physiologie , Labyrinthe vestibulaire/physiologie , Animaux , Électroencéphalographie , Électromyographie , Mâle , Souris , Souris de lignée C57BL , Polysomnographie
17.
J Neurosurg ; : 1-8, 2018 Jun 01.
Article de Anglais | MEDLINE | ID: mdl-29957115

RÉSUMÉ

OBJECTIVEAmid the public health controversy surrounding American football, a helmet that can reduce linear and rotational acceleration has the potential to decrease forces transmitted to the brain. The authors hypothesized that a football helmet with an outer shell would reduce both linear and rotational acceleration. The authors' objectives were to 1) determine an optimal material for a shock-absorbing outer shell and 2) examine the ability of an outer shell to reduce linear and/or rotational acceleration.METHODSA laboratory-based investigation was undertaken using an extra-large Riddell Revolution football helmet. Two materials (Dow Corning Dilatant Compound and Sorbothane) were selected for their non-Newtonian properties (changes in viscosity with shear stress) to develop an outer shell. External pads were attached securely to the helmet at 3 locations: the front boss, the side, and the back. The helmet was impacted 5 times per location at 6 m/sec with pneumatic ram testing. Two-sample t-tests were used to evaluate linear/rotational acceleration differences between a helmet with and a helmet without the outer shell.RESULTSSorbothane was superior to the Dow Corning compound in force reduction and recovered from impact without permanent deformation. Of 5 different grades, 70-duro (a unit of hardness measured with a durometer) Sorbothane was found to have the greatest energy dissipation and stiffness, and it was chosen as the optimal outer-shell material. The helmet prototype with the outer shell reduced linear acceleration by 5.8% (from 75.4g to 71.1g; p < 0.001) and 10.8% (from 89.5g to 79.8g; p = 0.033) at the side and front boss locations, respectively, and reduced rotational acceleration by 49.8% (from 9312.8 rad/sec2 to 4671.7 rad/sed2; p < 0.001) at the front boss location.CONCLUSIONSSorbothane (70 duro) was chosen as the optimal outer-shell material. In the outer-shell prototype helmet, the results demonstrated a 5%-10% reduction in linear acceleration at the side and front boss locations, and a 50% reduction in rotational acceleration at the front boss location. Given the paucity of publicly reported helmet-design literature and the importance of rotational acceleration in head injuries, the substantial reduction seen in rotational acceleration with this outer-shell prototype holds the potential for future helmet-design improvements.

18.
J Appl Biomech ; 34(5): 354-360, 2018 Oct 01.
Article de Anglais | MEDLINE | ID: mdl-29651910

RÉSUMÉ

This study aimed to compare head impact exposures between practices and games in football players ages 9 to 14 years, who account for approximately 70% of all football players in the United States. Over a period of 2 seasons, 136 players were enrolled from 3 youth programs, and 49,847 head impacts were recorded from 345 practices and 137 games. During the study, individual players sustained a median of 211 impacts per season, with a maximum of 1226 impacts. Players sustained 50th (95th) percentile peak linear acceleration of 18.3 (46.9) g, peak rotational acceleration of 1305.4 (3316.6) rad·s-2, and Head Impact Technology Severity Profile of 13.7 (24.3), respectively. Overall, players with a higher frequency of head impacts at practices recorded a higher frequency of head impacts at games (P < .001, r2 = .52), and players who sustained a greater average magnitude of head impacts during practice also recorded a greater average magnitude of head impacts during games (P < .001). The youth football head impact data quantified in this study provide valuable insight into the player exposure profile, which should serve as a key baseline in efforts to reduce injury.


Sujet(s)
Traumatismes cranioencéphaliques/prévention et contrôle , Football américain/traumatismes , Dispositifs de protection de la tête , Accélération , Adolescent , Phénomènes biomécaniques , Enfant , Traumatismes cranioencéphaliques/physiopathologie , Mouvements de la tête/physiologie , Humains , Mâle , États-Unis
19.
Int J Psychophysiol ; 132(Pt A): 87-92, 2018 10.
Article de Anglais | MEDLINE | ID: mdl-28986327

RÉSUMÉ

CONTEXT: There is a paucity of head impact biomechanics research focusing on youth athletes. Little is known about how youth subconcussive head impact tolerances are related to physical size and maturation. OBJECTIVE: To examine the effects of age, anthropometric and maturational status variability on head impact biomechanics. DESIGN: Cross-sectional. SETTING: Outdoor youth football facilities in South Carolina. PARTICIPANTS: Thirty-four male recreational youth football players, 8 to 13yrs. INTERVENTIONS: Categorized by CDC standards, independent variables were: age, height, mass, BMI, and estimated peak height velocity (PHV). Participants wore a designated head impact sensor (xPatch) on their mastoid process during practices and games. MAIN OUTCOME MEASURES: Linear acceleration (g) and rotational acceleration (rad/s2). RESULTS: Boys in the older age category had a greater linear (F=17.72; P<0.001) and rotational acceleration (F=10.74; P<0.001) than those in the younger category. Post-PHV boys had higher linear (F=9.09, P=0.002) and rotational (F=5.57, P=0.018) accelerations than those who were pre-PHV. Rotational, but not linear acceleration differed by height category with lowest impacts found for the tallest category, whereas both linear and rotational accelerations by mass differences favored average and heavy categories. BMI overweight boys, had the greatest linear (F=5.25; P=0.011) and rotational acceleration (F=4.13; P=0.260) means. CONCLUSION: Post-PHV boys who were older, taller and had longer legs, but who were not heavier, had higher impacts perhaps due to the type of impacts sustained. Taller boys' heads are above their peers possibly encouraging hits in the torso region resulting in lower impact accelerations. Obese boys did not have sequential results compared to boys in the other BMI categories probably due to league rules, player position, and lack of momentum produced.


Sujet(s)
Accélération , Développement de l'adolescent/physiologie , Traumatismes sportifs/physiopathologie , Phénomènes biomécaniques/physiologie , Indice de masse corporelle , Mensurations corporelles/physiologie , Développement de l'enfant/physiologie , Football américain/traumatismes , Traumatismes crâniens fermés/physiopathologie , Obésité pédiatrique/physiopathologie , Adolescent , Facteurs âges , Taille/physiologie , Commotion de l'encéphale/physiopathologie , Enfant , Études transversales , Humains , Mâle , Dispositifs électroniques portables
20.
J Sci Med Sport ; 21(2): 139-146, 2018 Feb.
Article de Anglais | MEDLINE | ID: mdl-29122475

RÉSUMÉ

OBJECTIVES: To quantify the magnitude, frequency, duration and distribution of head impact exposure in a women's rugby league competition. DESIGN: Prospective cohort study. METHODS: Twenty-one players had a wireless impact measuring device (X2Biosystems XPatch) behind their right ear during match participation. Head impact data were collected and downloaded for analysis. Median peak linear and rotational accelerations and impact locations between player positions were assessed using a Friedman repeated measures ANOVA on ranks with a Wilcoxon signed-rank test for post hoc analysis with a Bonferroni correction. RESULTS: A total of 1659 impacts to the head >10g were recorded (range 10g-91g) over the nine competition matches. There was a mean of 184±18 impacts per-match resulting in a mean of 14±12 impacts per-player per-match. The No. 8 prop recorded a mean of 29±27 impacts per-match, the No. 12 second-row forward recorded the highest median peak resultant linear acceleration (16g) per-match and the No. 11 second-row forward recorded the highest median peak resultant rotational acceleration (3696rad/s2). CONCLUSIONS: Our cohort of 21 female rugby league athletes were exposed to repetitive sub-concussive head impact exposure with an average of 14 impacts per-player per-match. Forwards were exposed to more impacts per-match than backs and these impacts were of higher magnitude. Most impacts occurred on the side of the head and were sustained during the second half of the game. Clinicians, coaches and players should be aware of the rates and magnitude of head impacts in female rugby league athletes.


Sujet(s)
Accélération , Football américain/traumatismes , Traumatismes crâniens fermés/épidémiologie , Accélérométrie/méthodes , Adulte , Analyse de variance , Femelle , Humains , Nouvelle-Zélande/épidémiologie , Études prospectives , Statistique non paramétrique , Facteurs temps , Dispositifs électroniques portables , Jeune adulte
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