Impact Attenuation Properties Research Articles

A comparison of sub-concussive impact attenuating capabilities of ice hockey helmets with and without XRD foam

To compare the impact attenuating capabilities between ice hockey helmets manufactured with and without XRD impact protection foam, worn with and without a XRD skullcap, at reducing sub-concussive head accelerations. Quasi-experimental laboratory. Ice hockey helmets were fit onto a Hybrid III 50th Head Form Head and dropped 25 times onto the left temporal side for each condition: XRD foam helmet, XRD foam helmet with XRD skullcap adjunct, non-XRD foam helmet, and non-XRD foam helmet with XRD skullcap adjunct. The helmets were dropped from a height that resulted in sub-concussive linear accelerations (25-80 g's). Using a tri-axial accelerometer, peak linear accelerations (g) were measured, and the average was used to compare impact attenuation properties across the four conditions. The highest linear accelerations were observed in the XRD foam helmet without skullcap (32.97 ± 0.61 g) and were significantly greater (p < 0.001) than the XRD helmet with skullcap (21.38 ± 0.76 g). The helmet without XRD foam elicited the lowest peak linear accelerations (16.10 ± 0.73 g) which were significantly lower than the XRD foam helmet regardless of whether the skullcap was added (p < 0.001). Although sub-concussive loads are potentially just as dangerous, much of the research regarding helmet and skullcap efficacy appears to be at high concussive impacts; <70 g's. The findings suggest that helmets with incorporated XRD foam, either within the design or added as an adjunct, are less effective at attenuating linear accelerations at sub-concussive levels than the low-density foam helmet.

Gradient shear thickening gel/Kevlar fabric multi-layer armor with enhanced impact attenuation property

Gradient shear thickening gel/Kevlar fabric multi-layer armor with enhanced impact attenuation property

How are the impact attenuation properties of men’s and women’s helmets affected after one season in professional ice hockey?

The purpose of this study was to investigate if the impact attenuation properties of ice hockey helmets change after being used for one season in a professional ice hockey league. Eighteen helmets from a male team and 10 helmets from a female team were compared to 13 new helmets. Every helmet was impact tested three times for two impact locations, side and front. The median peak linear acceleration for all front impacts were significantly higher ( p &lt; 0.05) for the helmets from the female team compared to the helmets from the male team. Compared to the new helmets, both men’s and women’s helmets had significantly lower median peak angular acceleration ( p &lt; 0.01) and peak angular velocity ( p&lt; 0.001). For side impacts, the women’s helmets had significantly higher peak linear acceleration compared to the men’s and new helmets ( p &lt; 0.001). Both men’s and women’s helmets had significantly higher peak angular acceleration compared to the new helmets ( p &lt; 0.001), and women’s helmets also had significantly higher peak angular acceleration compared to men’s helmets. Compared to men’s and new helmets, the results show that women’s helmets have worse impact attenuation properties after one season. However, all used helmets satisfied the passing threshold for test standards and the differences in calculated injury risk were small. This information may assist in establishing recommendations for the expected lifetime usage for ice hockey helmets and support manufacturers to develop safer ice hockey helmets.

Impact Mitigation Properties and Material Characterization of Women's Lacrosse Headgear.

The purpose of this study was to examine the impact attenuation properties of women's lacrosse headgear and to characterize mechanical properties of the materials of which they are composed. Impacts using a linear impactor (2.2, 2.9, and 5.0m/s) and a projectile shooter (13.4 and 27.0m/s) were applied to a Hybrid III 50th male head-neck assembly at six impact locations to replicate realistic women's lacrosse head impacts. Individual materials that make up the headgear were tested in compression at two quasi-static strain rates, 0.01/s and1/s, and 100/s using uniaxial test machines. For the linear impactor tests, results showed a significant decrease in peak linear and rotational acceleration (PLA and PRA), peak rotational velocity (PRV), head injury criteria and brain injury criteria in the helmeted impacts (p < 0.022). During the ball impacts PRV and PRA were significantly lower for both helmeted conditions compared with no helmet (p < 0.01). Material characterization tests indicated a range of rate effects in these materials ranging from weak to pronounced, and these effects correspondingly influenced the strain energy density graphs. The connection of the materials' rate effects to the performance of the headgear is described in general and in relation to the impact tests.

Instrumentation and preliminary evaluation of a drop tower tester for low and medium impact energy

Soft, porous structures imbibed with liquids have good impact attenuation properties. Literature survey reveals a continuous need for new impact tests to assess impact response for the newly developed soft, porous materials. This paper presents a versatile drop tower tester which is based on an impactor that slides inside a transparent tube. The test rig is equipped with high-speed transducers (force and acceleration) and a laser system used to measure the deformation of the experimental cell. A high-speed camera records subtle details of the impact that are not are visible with the naked eye. Preliminary experiments made on dry and imbibed soft fibrous tridimensional textile have shown good repeatability during impact. The experiments presented validate the experimental procedure, based on the analysis of the contact force-displacement curve, acceleration, and impact force-transmitted force. The obtained results demonstrate that true impact response is described with high resolution.

ロングパイル人工芝における水平方向衝撃力の検討

The purpose of this study is to consider the two-dimensional impact force applied to the artificial turf with spike studs, especially focused on the horizontal impact force. The shock attenuation properties of sports surfaces are usually evaluated by reduction of maximum input force, for example, WA (World Athletics) adopted the EN14808 as the vertical force attenuation test. Otherwise, the horizontal impact attenuation has not been treated as the regulation of impact, although the most of impact in sports activities performed with diagonal impact force, including horizontal impact forces. In previous studies, we developed the two-dimensional impact test device with parallelogram structure which divide the vertical impact force to two-dimensional impact forces simultaneously. The impact test device can be set the various impact weights to generate the impact forces resembled to the ground reaction force in human running. And proposed the method for two-dimensional impact attenuation, named DFR (dynamic force reduction) because the horizontal impact forces were very dependent to the initial impact angle. Although the proposed method could evaluate the attenuation of various impact forces, there are some inappropriate cases especially in horizontal impact force attenuation. As the results, the horizontal impact force is very dependent to the impact angle and is independent to the vertical impact attenuation properties. Additionally, rubber chip as an infill material may cause increasing of horizontal impact force because it makes larger horizontal displacement in diagonal impact.

Comparison of branded rugby headguards on their effectiveness in reducing impact on the head

AimTo compare the available brands of rugby headguards and evaluate their impact attenuation properties at various locations on the cranium, with regard to concussion prevention.MethodsSeven different branded headguards were fitted...

Shock-absorbing aggregates beneath playground equipment: grain properties and moisture content

ObjectivesTo assess the influence of grain size distribution and moisture condition on aggregates’Setting and methodsImpact attenuation of sands and gravels was tested using a guided headform with a uniaxial accelerometer...

Impact attenuation capabilities of football and lacrosse helmets

Although the National Operating Committee on Standards for Athletic Equipment (NOCSAE) standards are similar for football and lacrosse helmets, it remains unknown how helmets for each sport compare on drop tests. Due to the increased concern over head injury in sport and the rapid growth in lacrosse participation, it is useful to compare the performance of various football and lacrosse helmets. Therefore, the goal of this study was to document the impact attenuation properties of football and lacrosse helmets and to identify the relative performance between helmets for the two sports. Six models of football and six models of lacrosse helmets were tested using a drop tower at three prescribed velocities and six locations on the helmets. A repeated measures ANOVA was conducted to determine the effect of sport on Gadd Severity Index (GSI) scores and linear accelerations. The interaction between location and sport was significant at the low (F2.64,89.71=7.68, P<.001, η2=.025), medium (F2.85,96.85=16.78, P<.001, η2=.085), and high (F2.96,100.69=16.67, P<.001, η2=.093) velocities for GSI scores. When comparing peak acceleration results, we found a significant interaction between location and sport for the medium (F3.40,115.616=5.57, P=.001, ω2=.031) and high (F3.46,117.50=6.42, P<.001, ω2=.047) velocities. Features of football helmet design provide superior protection compared to lacrosse helmets. Further investigation of helmet design features across sports will yield insight into how design features influence helmet performance during laboratory testing.

Age Does Not Affect the Material Properties of Expanded Polystyrene Liners in Field-Used Bicycle Helmets.

Bicycle helmet foam liners absorb energy during impacts. Our goal was to determine if the impact attenuation properties of expanded polystyrene (EPS) foam used in bicycle helmets change with age. Foam cores were extracted from 63 used and unused bicycle helmets from ten different models spanning an age range of 2-20 yrs. All cores were impact tested at a bulk strain rate of 195 s(-1). Six dependent variables were determined from the stress-strain curve derived from each impact (yield strain, yield stress, elastic modulus, plateau slope, energy at 65% compression, and stress at 65% compression), and a general linear model was used to assess the effect of age on each dependent variable with density as a covariate. Age did not affect any of the dependent variables; however, greater foam density, which varied from 58 to 100 kg/m(3), generated significant increases in all of the dependent variables except for yield strain. Higher density foam cores also exhibited lower strains at which densification began to occur, tended to stay within the plateau region of the stress-strain curve, and were not compressed as much compared with the lower density cores. Based on these data, the impact attenuation properties of EPS foam in field-used bicycle helmets do not degrade with the age.

Impact attenuation properties of new and used lacrosse helmets

The National Operating Committee on Standards for Athletic Equipment (NOCSAE) has developed impact attenuation thresholds that protective helmets worn in sport must meet to be commercially available in an attempt to prevent injury. It remains unknown how normal helmet use in athletic activity alters the force attenuation ability of lacrosse helmets. We tested 3 new and 3 randomly selected used helmets from 2 popular lacrosse models (Cascade Pro7, Cascade CPXR). All used helmets had been worn for 3 collegiate seasons prior to testing and had never been refurbished. Helmets were drop-tested using 3 prescribed impact velocities at 6 locations according to the NOCSAE lacrosse helmet standard, and we compared the Gadd Severity Index (GSI) scores between new and used helmets using a repeated measure ANOVA with location as the repeated variable and data separated by impact velocity. All 12 helmets passed the NOCSAE GSI threshold for all testing conditions; however 1 used helmet shell cracked resulting in a failed test. We found a significant main effect for helmet age at the low (F5,50=2.98, P=.02), medium (F5,50=3.71, P=.006), and high (F5,50=2.70, P=.03) velocities. We suspect that helmet use can degrade materials under some conditions, but improve performance in others due to changes in helmet composition from use. The clinical implications of the differences in GSI scores noted remain unclear. Because one helmet shell cracked resulting in a failed test, used helmets should be regularly inspected for cracks or other signs of mechanical fatigue that may weaken helmet integrity.

The Influence of Body Mass Index and Gender on the Impact Attenuation Properties of Flooring Systems

The biomechanical effectiveness of safety floors has never been assessed during sideways falls with human volunteers. Furthermore, the influence of body mass index (BMI) and gender on the protective capacity of safety floors is unknown. The purpose of this study was to test whether safety floors provide greater impact attenuation compared with traditional flooring, and whether BMI and gender modify their impact attenuation properties. Thirty participants (7 men and 7 women of low BMI; 7 men and 9 women of high BMI) underwent lateral pelvis release trials on 2 common floors and 4 safety floors. As a group, the safety floors reduced peak force (by up to 11.7%), and increased the time to peak force (by up to 25.5%) compared with a traditional institutional grade floor. Force attenuation was significantly higher for the low BMI group, and for males. Force attenuation was greatest for the low BMI males, averaging 26.5% (SD = 3.0) across the safety floors. These findings demonstrate an overall protective effect of safety floors during lateral falls on the pelvis, but also suggest augmented benefits for frail older adults (often with low body mass) who are at an increased risk of hip fracture.

A influência do uso acumulado de calçados de corrida sobre a força de reação do solo e as respostas de pressão plantar

Acredita-se que a eficiência do calçado seja afetada pelo uso prolongado, mas as alterações biomecânicas ainda não estão bem compreendidas. O objetivo deste estudo é analisar a influência do uso de calçados de corrida na força de reação do solo e os parâmetros de pressão plantar. Três corredores do sexo masculino receberam quatro calçados de corrida para usarem em suas sessões de treinamento. O Sistema Gaitway e o Sistema de F-scan foram usados para registrar a força de reação do solo e parâmetros pressão plantar em diferentes regiões do pé. As coletas ocorreram em quatro momentos: novo e 100, 200 e 300 km de uso. O primeiro pico diminuiu da condição novo para os 300 km de uso (p &lt; 0,01). A taxa de crescimento 1 diminuiu aos 200 km em relação às condições novas (p &lt; 0,01). A área total aumentou aos 100 km (p &lt; 0,01) de uso e manteve valores semelhantes e mais altos até 300km. No pico de pressão antepé, houve uma diminuição progressiva (p &lt; 0,01) como o aumento quilometragem e os valores de pico de pressão do hálux foram significativamente menores (p &lt; 0,01) aos 300 km do que na condição novo. Como o primeiro pico, a taxa de crecimento 1 e os picos de pressão plantar não aumentaram e a área de contato plantar total aumentou. Conclui-se que o calçado de corrida não sofreu alterações consistentes na força de reação do solo e na pressão plantar após 300 km de uso.

A Review of Football Injuries on Third and Fourth Generation Artificial Turfs Compared with Natural Turf

Football codes (rugby union, soccer, American football) train and play matches on natural and artificial turfs. A review of injuries on different turfs was needed to inform practitioners and sporting bodies on turf-related injury mechanisms and risk factors. Therefore, the aim of this review was to compare the incidence, nature and mechanisms of injuries sustained on newer generation artificial turfs and natural turfs. Electronic databases were searched using the keywords 'artificial turf', 'natural turf', 'grass' and 'inj*'. Delimitation of 120 articles sourced to those addressing injuries in football codes and those using third and fourth generation artificial turfs or natural turfs resulted in 11 experimental papers. These 11 papers provided 20 cohorts that could be assessed using magnitude-based inferences for injury incidence rate ratio calculations pertaining to differences between surfaces. Analysis showed that 16 of the 20 cohorts showed trivial effects for overall incidence rate ratios between surfaces. There was increased risk of ankle injury playing on artificial turf in eight cohorts, with incidence rate ratios from 0.7 to 5.2. Evidence concerning risk of knee injuries on the two surfaces was inconsistent, with incidence rate ratios from 0.4 to 2.8. Two cohorts showed beneficial inferences over the 90% likelihood value for effects of artificial surface on muscle injuries for soccer players; however, there were also two harmful, four unclear and five trivial inferences across the three football codes. Inferences relating to injury severity were inconsistent, with the exception that artificial turf was very likely to have harmful effects for minor injuries in rugby union training and severe injuries in young female soccer players. No clear differences between surfaces were evident in relation to training versus match injuries. Potential mechanisms for differing injury patterns on artificial turf compared with natural turf include increased peak torque and rotational stiffness properties of shoe-surface interfaces, decreased impact attenuation properties of surfaces, differing foot loading patterns and detrimental physiological responses. Changing between surfaces may be a precursor for injury in soccer. In conclusion, studies have provided strong evidence for comparable rates of injury between new generation artificial turfs and natural turfs. An exception is the likely increased risk of ankle injury on third and fourth generation artificial turfs. Therefore, ankle injury prevention strategies must be a priority for athletes who play on artificial turf regularly. Clarification of effects of artificial surfaces on muscle and knee injuries are required given inconsistencies in incidence rate ratios depending on the football code, athlete, gender or match versus training.

Impact Attenuation And Kinetic Characteristics Of Cross Training Shoes In Landing And Jumping Activities

Very few footwear studies have examined athletic shoes designed for sports other than running. Cross-training footwear is designed to meet needs of a variety of sports and sport training environments with key features that include generating power for performance and attenuating impacts for injury prevention. PURPOSE To examine kinetic characteristics of impact attenuation in landing and power generation in jumping of four different cross training shoes. METHODS Ten healthy male recreational athletes (age:21.5±2.5 yrs) performed five step-off landing trials and five maximum vertical jumping trials in each of four cross-training shoes (from three leading footwear manufacturers). Right sagittal kinematic data (120 Hz), ground reaction forces (GRF,1200 Hz), and forehead and distal tibia accelerations (ACC, landing only) were measured simultaneously. The landing height was determined individually based upon potential energy of a “mid-size” person (80 kg) landing from a 0.6 m height. Material tests were performed on selected sizes of each shoe model.A one-way repeated measures ANOVA and post-hoc comparisons (p < 0.05) were performed on selected variables. RESULTS The results from the landing trials showed that Shoes A (23 N/kg) and B (26 N/kg) had significantly smaller forefoot peak GRF than Shoes C (29 N/kg) and D 28 N/kg). Shoes A (2274 N/kg/s) and B (2630 N/kg/s) also showed lower loading rate associated with the forefoot contact than Shoes C (3316 N/kg/s) and D (3336 N/kg/s). No significant changes were seen in ACC data. The jumping GRF results normalized to the individual jump height indicated significantly greater peak power for Shoes C (50 Wm/kg) and D (51 Wm/kg) compared to A (48 Wm/kg). Maximum peak GRF for Shoe D (16 Nm/kg) was greater than Shoe A (15 Nm/kg). In addition, kinematic data showed not clear trends in landing or jumping trials. The material testing indicated that Shoes A and B had the smallest forefoot stiffness values (9.2 and 9.6 N/mm) compared to Shoe C and D (18.0 and 12.7 N/mm) obtained in a fixibility test. Energy loss for Shoes A and B (41%and 43%) were greater than Shoes C and D (33 and 35%). CONCLUSIONS The results suggested that the Shoes A and B showed slightly better forefoot impact attenuation properties. Shoe D and C demonstrated better jumping performance than Shoe A. But better performance may come at a price of decreased cushioning.

Impact Attenuation And Kinetic Characteristics Of Cross Training Shoes In Landing And Jumping Activities

Very few footwear studies have examined athletic shoes designed for sports other than running. Cross-training footwear is designed to meet needs of a variety of sports and sport training environments with key features that include generating power for performance and attenuating impacts for injury prevention. PURPOSE To examine kinetic characteristics of impact attenuation in landing and power generation in jumping of four different cross training shoes. METHODS Ten healthy male recreational athletes (age:21.5±2.5 yrs) performed five step-off landing trials and five maximum vertical jumping trials in each of four cross-training shoes (from three leading footwear manufacturers). Right sagittal kinematic data (120 Hz), ground reaction forces (GRF,1200 Hz), and forehead and distal tibia accelerations (ACC, landing only) were measured simultaneously. The landing height was determined individually based upon potential energy of a “mid-size” person (80 kg) landing from a 0.6 m height. Material tests were performed on selected sizes of each shoe model.A one-way repeated measures ANOVA and post-hoc comparisons (p < 0.05) were performed on selected variables. RESULTS The results from the landing trials showed that Shoes A (23 N/kg) and B (26 N/kg) had significantly smaller forefoot peak GRF than Shoes C (29 N/kg) and D 28 N/kg). Shoes A (2274 N/kg/s) and B (2630 N/kg/s) also showed lower loading rate associated with the forefoot contact than Shoes C (3316 N/kg/s) and D (3336 N/kg/s). No significant changes were seen in ACC data. The jumping GRF results normalized to the individual jump height indicated significantly greater peak power for Shoes C (50 Wm/kg) and D (51 Wm/kg) compared to A (48 Wm/kg). Maximum peak GRF for Shoe D (16 Nm/kg) was greater than Shoe A (15 Nm/kg). In addition, kinematic data showed not clear trends in landing or jumping trials. The material testing indicated that Shoes A and B had the smallest forefoot stiffness values (9.2 and 9.6 N/mm) compared to Shoe C and D (18.0 and 12.7 N/mm) obtained in a fixibility test. Energy loss for Shoes A and B (41%and 43%) were greater than Shoes C and D (33 and 35%). CONCLUSIONS The results suggested that the Shoes A and B showed slightly better forefoot impact attenuation properties. Shoe D and C demonstrated better jumping performance than Shoe A. But better performance may come at a price of decreased cushioning.

Comparative performance of playground surfacing materials including conditions of extreme non-compliance

Objective: A recent case series study found that only 4.7% of 402 playgrounds in which arm fractures occurred in Victorian schools complied with the recommended 20 cm depth of tanbark....

Improving head protection for cyclists, motorcyclists, and car occupants.

It appears from this review of the literature that both linear and angular accelerations are important in the production of injury to the brain. These mechanical inputs to the head result in differential movements or strains in the contents of the head. These strains, if large enough, produce the irreversible loss of function or physical disruptions of neural or other tissue, observed following head impacts. Owing to the difficulties in measuring these strains, criteria for injury levels are written in terms of external movements of the head, and for the more easily measurable linear acceleration rather than angular acceleration. Helmets for motorcyclists provide adequate protection for impacts up to about 8 m/s. Their performance could be improved for front and side impacts to the head, and by matching liner and skull characteristics. Bicycle helmets have both hard and soft shell models with similar impact attenuation properties. The compulsory wearing of these helmets in Victoria appears to have reduced the number of head injuries sustained. For car occupants, only in the U.S.A. is there a measure of the degree of head protection, in that the Head Injury Criterion is used for 50 km/h frontal impacts. Car occupants appear to be susceptible to severe head injury in side impacts. Considerable improvements could be made by providing impact attenuation in the head contact areas on the door, roof and B-pillar. The seat belt provides protection in frontal impacts, which could be improved further with the addition of an air bag, or by wearing a helmet.