Brain trauma exposure for American tackle football players 5 to 9 and 9 to 14 years of age.

American football helmets used by youth players are currently designed and tested to the same standards as professionals. The National Operating Committee on Standard and Safety requested research aiming at understanding the differences in brain trauma in youth American football for players aged five to nine and nine to fourteen years old to inform a youth specific American football standard. Video analysis and laboratory reconstructions of head impacts were undertaken to measure differences in head impact frequency, event types, and magnitudes of maximum principal strain (MPS) for the two age groups. Overall frequencies and frequencies for five categories of MPS representing different magnitudes of risk were tabulated. The MPS categories were very low (<0.08), low (0.08-0.169), medium (0.17-0.259), high (0.26-0.349) and very high (>0.35). Both cohorts experienced a majority of head impacts (>56%) at very low magnitude of MPS. Youth American football players aged 9-14 yrs. sustained a greater frequency of head impacts at MPS between 0.08 and 0.169 % associated with changes in brain structure and function. There were no differences in overall frequency, or in frequency of head impacts in other categories of MPS. The proportion of impacts considered injurious (MPS > 0.08) was greater in the 5-9 group (44%), than the 9-14 group (39%), and impacts above 0.35 % were only reported for the younger age group. The larger helmet-to-shoulder ratio in the younger age groups may have contributed to this finding suggesting that youth American football players under the age of nine would benefit from a child-specific football helmet.

Traumatic brain injuries: the influence of the direction of impact.

BACKGROUND: Head impact direction has been identified as an influential risk factor in the risk of traumatic brain injury (TBI) from animal and anatomic research; however, to date, there has been little investigation into this relationship in human subjects. If a susceptibility to certain types of TBI based on impact direction was found to exist in humans, it would aid in clinical diagnoses as well as prevention methods for these types of injuries. OBJECTIVE: To examine the influence of impact direction on the presence of TBI lesions, specifically, subdural hematomas, subarachnoid hemorrhage, and parenchymal contusions. METHODS: Twenty reconstructions of falls that resulted in a TBI were conducted in a laboratory based on eyewitness, interview, and medical reports. The reconstructions involved impacts to a Hybrid III anthropometric dummy and finite element modeling of the human head to evaluate the brain stresses and strains for each TBI event. RESULTS: The results showed that it is likely that increased risk of incurring a subdural hematoma exists from impacts to the frontal or occipital regions, and parenchymal contusions from impacts to the side of the head. There was no definitive link between impact direction and subarachnoid hemorrhage. In addition, the results indicate that there is a continuum of stresses and strain magnitudes between lesion types when impact location is isolated, with subdural hematoma occurring at lower magnitudes for frontal and occipital region impacts, and contusions lower for impacts to the side. CONCLUSION: This hospital data set suggests that there is an effect that impact direction has on TBI depending on the anatomy involved for each particular lesion.

Deformation mechanisms and impact attenuation characteristics of thin-walled collapsible air chambers used in head protection.

Head injuries are a major cause of morbidity and mortality worldwide, many resulting from sporting activities. There is a constant need in the head protection industry for improved methods to manage impacts and to reduce the risk of mild and severe head injuries. Contemporary head protection primarily consists of foam with several inherent disadvantages, including a limited ability to provide effective energy absorption under both low and high impact velocities. Recently, thin-walled collapsible chambers were engineered to address this problem and have been implemented into sport helmets. The chambers consist of four engineering elements which define their dynamic performance: geometry, air volume, material, and venting system. This research analysed the contribution of air flow through an orifice to the chamber's management of impact energy. The objective of this study was to determine the effect of the chamber's vent diameter and material stiffness on peak force and venting rate during an impact. Two material stiffnesses (thermoplastic polyurethane 45D and thermoplastic polyurethane 90A) and five vent diameters (1 mm, 2 mm, 3 mm, 4 mm, and 5 mm) were tested at three inbound velocities (1.3 m/s, 2.3 m/s, and 3.0 m/s). Each chamber was impacted ten times using a monorail drop system. Analysis of the results revealed that the material stiffness, vent diameter, and inbound velocity all had a significant effect on peak force and venting rate (p < 0.001). Under low inbound velocities the largest vent diameters transmitted a lower force than the smallest vent, while this relationship reversed at high inbound velocities. Under low velocities the air flowrate was negatively correlated and the flow duration was positively correlated to the peak force. Under high velocities, the air flowrate was positively correlated and the duration was negatively correlated to the peak force. This suggested that, under low velocities, chambers performed optimally when air was dissipated quickly, for a short duration; however, as the chamber approached a critical failure region, the increased duration and decreased velocity of air released prevented higher peak forces. This research confirmed that the differences in vent diameter and material stiffness significantly affected the impact force characteristics of engineered thin-walled collapsible chambers.

Dynamic joint analysis as a method to document coordination disabilities associated with Parkinson's disease.

OBJECTIVE: The purpose of the present study was to introduce dynamic joint analysis and subsequent phase partitioning of the movement pattern as a method for investigating the force control deficits associated with Parkinson's disease. DESIGN: Pilot data were collected from four non-impaired individuals and four patients afflicted with Parkinson's disease while performing arm movements of different spatiotemporal features. BACKGROUND: Investigation of motor performance in Parkinson's patients has related the clinically observed symptoms to the ability to control muscular force. METHODS: Experimental movements were filmed using a high speed camera operating at 200 Hz. The mechanical power characteristics of the elbow and shoulder were determined by applying inverse dynamic solutions to the kinematic data. Movement was reflected in a series of goal-directed phases describing the functional role of muscle activity across the joint. RESULTS: The analysis revealed that Parkinson's disease impairs the ability of the muscles to produce the energy required for performing ballistic, segmental movements. Moreover, patients demonstrated greater difficulty in controlling a two-joint task as opposed to a single-joint one; this was reflected by additional phases of activity at the elbow. CONCLUSIONS: Slowness of movement is associated with the inappropriate scaling of the muscle force, as well as with the limited use of motion-dependent forces in accelerating distal segment movement.

Uma comparaçäo biomecânica de dois sistemas de assento para crianças portadoras de paralisia cerebral moderada / A biomechanics comparison of two seating systems for children carried of moderate cerebral palsy

O objetivo deste estudo foi o de comaparar variáveis biomecânicas selecionadas do ato de sentar para crianças portadoras de paralisia cerebral moderada em dois sistema convencional. Dezenove crianças com idade variando de cinco a treze anos, portadoras de paralisia cerebral moderada espástica, participaram do estudo. Pontos de referência foram marcados e fotografias foram tiradas zero, cinco e dez minutos após as crianças atingirem posiçäo sentada a mais cômoda em ambos os sistemas. Após, os sujeitos foram instruídos para que se movessem para uma posiçäo funcional posterior e duas fotografias foram tiradas nesta posiçäo, após a qual os sujeitos retornaram à posiçäo relaxada e duas chapas finais foram feitas. Uma análise de variância 2 x 4 (sistema versus postura) para medidas repetidas foi realizada para cada uma das dez variáveis dependentes pré-selecionadas. Os resultados do estudo mostraram que o sistema de testes foi bem sucedido em distribuir a massa corporal superior reduzindo os momentos negativos lombares e aumentando os momentos positivos isquiáticos. Conclui-se, portanto, que o sistema de testes melhorou a postura sentada de crianças portadoras de paralisia cerebral moderada

Relationships of age and sex with range of motion of seventeen joint actions in humans.

This study investigated the relationship of age and sex with the range of motion of seventeen joint actions at eight joints. A sample of 190 male and female subjects ranging in age from 18 to 88 years were measured using a modified version of Leighton's (1942) procedures. The data were analyzed to obtain test-retest reliability, to determine significant differences in flexibility across age, and to assess sex differences in flexibility. The following conclusions were made: a general decline in flexibility of joints occurs with age; upper extremity joints do not readily reflect this decreased flexibility with age; the configuration of flexibility is specific to the joint action and; females have greater flexibility than males throughout life.