Injury Biomechanics

To gain insight into the adaptive response of human tendon to paralysis, we compared the mechanical properties of the in vivo patellar tendon in six men who were spinal cord–injured (SCI) and eight age-matched, able-bodied men. Measurements were taken by combining dynamometry, electrical stimulation, and ultrasonography. Tendon stiffness and Young's modulus, calculated from force–elongation and stress–strain curves, respectively, were lower by 77% (P < 0.01) and 59% (P < 0.05) in the SCI than able-bodied subjects. The cross-sectional area (CSA) of the tendon was 17% smaller (P < 0.05) in the SCI subjects, but there was no difference in tendon length between the two groups. Our results indicate that paralysis causes substantial deterioration of the structural and material properties of tendon. This needs to be taken into consideration in the design of electrical stimulation protocols for rehabilitation and experimental purposes, and when interpreting changes in the contractile speed of paralyzed muscle. Muscle Nerve, 2005

A powerful tool for investigating the physical process producing head trauma is finite element (FE) modeling. In this paper, we present a 3D FE model of the human head that accounts for important geometric characteristics of the various components within the human head through an efficient magnetic resonance imaging voxel-based mesh generation method. To validate the FE model, a previous cadaver experiment of frontal impact is simulated, and this is where heretofore unknown wave patterns are discovered. The model is run under either of two extreme assumptions concerning the head-neck junction-free or fixed-and the experimental measurements are well bounded by the computed pressures from the two boundary conditions. In both cases the impact gives rise to not only a fast pressure wave but also a slow and spherically convergent shear stress wave which is potentially more damaging to the brain tissue.

Soccer is the world's most popular sport and unique in that players use their unprotected heads to intentionally deflect, stop, or redirect the ball for both offensive and defensive strategies. Headed balls travel at high velocity pre-and postimpact. Players, coaches, parents, and physicians are justifiably concerned with soccer heading injury risk. Furthermore, risk of long-term neurocognitive and motor deficits caused by repetitively heading a soccer ball remains unknown. We review the theoretical concerns, the results of biomechanical laboratory experiments, and the available clinical data regarding the effects of chronic, subconcussive head injury during heading in soccer.

Knee abduction/adduction moment and knee internal rotation moment are known surrogate measures of anterior cruciate ligament (ACL) load during tasks like sidestepping and single-leg landing. Previous experimental literature has shown that a variety of kinematic strategies are associated or correlated with ACL injury risk; however, the optimal kinematic strategies needed to reduce peak knee moments and ACL injury are not well understood. To understand the complex, multifaceted kinematic factors underpinning ACL injury risk and to optimize kinematics to prevent the ACL injury, a musculoskeletal modeling and simulation experimental design was used. A 14-segment, 37-degree-of-freedom, dynamically consistent skeletal model driven by force/torque actuators was used to simulate whole-body single-leg jump landing kinematics. Using the residual reduction algorithm in OpenSim, whole-body kinematics were optimized to reduce the peak knee abduction/adduction and internal/external rotation moments simultaneously. This optimization was repeated across 30 single-leg jump landing trials from 10 participants. The general optimal kinematic strategy was to bring the knee to a more neutral alignment in the transverse plane and frontal plane (featured by reduced hip adduction angle and increased knee adduction angle). This optimized whole-body kinematic strategy significantly reduced the peak knee abduction/adduction and internal rotation moments, transferring most of the knee load to the hip.

The Hybrid III 50th percentile male anthropomorphic test device (ATD) is the most widely used human impact testing surrogate and has historically been used in automotive or military testing. More recently, this ATD is finding use in applications evaluating athletic helmet protectivity, quantifying head impact dosage and estimating injury risk. But ATD head-neck response has not been quantified in omnidirectional athletic-type head impacts absent axial preload. It is probable that headgear injury reduction that can be quantified in a laboratory, including in American football, boxing, hockey, lacrosse and soccer, is related to a number of interrelated kinetic and kinematic factors, such as head center of gravity linear acceleration, head angular acceleration, head angular velocity, occipito-cervical mechanics and neck stiffness. Therefore, we characterized ATD head-neck dynamic response to direct head impacts in a series of front, oblique front and lateral head impacts.

ABSTRACT – Dating to Colonel John Paul Stapp MD in 1975, scientists have desired to measure live human head impacts with accuracy and precision.  But no instrument exists to accurately and precisely quantify single head impact events.  Our goal is to develop a practical single event head impact dosimeter known as “Intelligent Mouthguard” and quantify its performance on the benchtop, in vitro and in vivo. 
In the Intelligent Mouthguard hardware, limited gyroscope bandwidth requires an algorithm-based correction as a function of impact duration.  After we apply gyroscope correction algorithm, Intelligent Mouthguard results at time of CG linear acceleration peak correlate to the Reference Hybrid III within our tested range of pulse durations and impact acceleration profiles in American football and Boxing in vitro tests: American football, IMG=1.00REF-1.1g, R2=0.99; maximum time of peak XYZ component imprecision 3.6g and 370rad/s2; maximum time of peak azimuth and elevation imprecision 4.8° and 2.9°; maximum average XYZ component temporal imprecision 3.3g and 390rad/s2.  Boxing, IMG=1.00REF-0.9g, R2=0.99, R2=0.98;  maximum time of peak XYZ component imprecision 3.9g and 390rad/s2, maximum time of peak azimuth and elevation imprecision 2.9° and 2.1°; average XYZ component temporal imprecision 4.0g and 440rad/s2.  In vivo Intelligent Mouthguard true positive head impacts from American football players and amateur boxers have temporal characteristics (first harmonic frequency  from 35Hz to 79Hz) within our tested benchtop (first harmonic frequency <180Hz) and in vitro (first harmonic frequency <100Hz) ranges. 
Our conclusions apply only to situations where the rigid body assumption is valid, sensor-skull coupling is maintained and the ranges of tested parameters and harmonics fall within the boundaries of harmonics validated in vitro.  For these situations, Intelligent Mouthguard qualifies as a single event dosimeter in American football and Boxing.

Background: Athletes suffering an anterior cruciate ligament injury tend to exhibit similar body postures that in sidestep cutting are associated with increased knee moments. This relationship, however, has not been investigated in landing. Catching a ball in different overhead positions may affect landing postures and knee joint moments. This study investigated these possible relationships. It was anticipated that some joint postures would be associated increased knee loads during the landing task.
Methods: Twenty-five healthy male team sports athletes performed four variations of a landing task. Full body kinematics were identified at initial contact. Peak flexion, valgus and internal rotation moments at the knee, measured during early landing, were normalized to mass and height and statistically compared. Intra-participant correlations were performed between all kinematics and each moment. Mean slopes for each correlation were used to identify the existence of relationships between full body kinematics and knee joint moments.
Findings: Landing after an overhead catch when the ball moved towards a player’s support leg resulted in increased peak valgus moments. These increased valgus moments were correlated with increased knee flexion, hip flexion, and torso lean, as well as torso rotation towards the support leg, and foot and knee external rotation. Increased internal rotation moments were correlated with reduced hip abduction and external rotation, increased ankle inversion, knee external rotation and torso lean away from the support leg.
Interpretation: Learning to land with techniques that do not reflect postures associated with high knee moments may reduce an athlete’s risk of non-contact anterior cruciate ligament injury.

Background: Lack of the neuromuscular control during locomotion in the knee joint leads to an increased risk of anterior cruciate ligament (ACL) injury in children. Hence, we aimed to explore the effects of a repetitive, model-oriented, and self-organized approach on lower limb kinematics during gait in children. Methods: In randomized controlled trial, 36 children with 4 ± 0.79 years of age from the children gym were randomly (a lottery method) allocated into three groups, including (1) the model-oriented (n = 10), (2) Differential Learning (n = 11), and (3) control (n = 10) groups. Kinematic data of hip, knee, and ankle joints in the sagittal plane were recorded by a GoPro camera at the moments of heel-ground contact and toe-off the ground before and after a 6-week intervention (two sessions per week). Results: The results indicate a 35% post-intervention increase of ankle dorsiflexion (95% CI: − 5.63 _ − 0.96) in the moment of heel-ground contact in the model-oriented group; however, knee flexion (95% CI: − 1.05 _ 8.34) and hip flexion (95% CI: 3.01 _ 11.78) were respectively decreased by 20% and 20%. After the intervention, moreover, ankle plantar flexion (95% CI: − 9.18 _ − 2.81) and hip extension (95% CI: − 12.87 _ − 3.72) have respectively increased by 37% and 37%, while knee flexion (95% CI: 3.49 _ 11.30) showed a %16 decrease in the moment of toe off the ground. As for the Differential Learning group, ankle dorsiflexion (95% CI: − 5.19 _ − 1.52) increased by 33%, and knee (95% CI: 0.60 _ 5.76) and hip flexion (95% CI: 2.15 _ 7.85) respectively decreased by 17% and 17% at the moment of the heelground contact following the intervention. At toe lifting off the ground, the plantar flexion (95% CI: − 7.77 _ − 2.77) increased by 35%, knee flexion (95% CI: 2.17 _ 7.27) decreased to 14%, and hip extension (95% CI: − 9.98 _ − 4.20) increased by %35 following the intervention for the Differential Learning group subjects. Based on the results obtained from the one-way ANOVA, there was a significant difference between these groups and the control group in all kinematic gait variables (p ≤ 0.05). However, no statistically significant differences were found between the two experimental groups. Conclusions: The results implied that the model-oriented repetitive and the self-organized Differential Learning approach were both appropriate to alter the kinematic gait pattern in the 3-5-year-old children. Previous research has almost exclusively recommended a model-oriented approach to change kinematic patterns and preventing noncontact motor injuries. However, the present study showed that the Differential Learning approach can help children to achieve the same goal by continuously changing environments and stimulating challenges.

In contrast to most scientific disciplines, sports science research has been characterized by comparatively little effort investment in the development of relevant phenomenological models. Scarcer yet is the application of said models in the practical domain. The present paper presents a framework which allows resistance training practitioners (coaches or athletes themselves) to employ a recently proposed model of neuromuscular engagement and adaptation in actual training program design. The first novelty concerns the monitoring aspect of coaching. A method for extracting training performance characteristics from loosely constrained video sequences, effortlessly and with minimal human input, using computer vision is described. The extracted data is subsequently used to infer the value of the parameters of the underlying neuromuscular model. This is achieved by using known differential equations describing the motion of the resistance during a particular exercise, in what is usually termed the inverse dynamics problem. Lastly, a computer simulation of hypothetical training bouts, using athlete specific capability parameters, is used to predict the effected adaptation and with it the changes in performance. The software developed and for the first time described here allows the practitioner to manipulate hypothetical training parameters and immediately see their effect on predicted adaptation for a specific athlete. Thus, this work presents a holistic view of the monitoring-assessment-adjustment loop. By bridging the gap between the theoretical and applied aspects of sports science, the present contribution serves to strongly encourage a further research focus on the development of more general, comprehensive models in this field.

Eccentric hamstring strength is an aetiological risk factor for soccer
injury. The temporal pattern of recovery post-exercise is critical in
injury management. 18 male professional soccer players completed
baseline assessments of eccentric hamstring strength at isokinetic
speeds of 60, 150 and 300°· s−1. Post SAFT90 measures were repeated
immediately, + 24 hrs, + 48 hrs and + 72 hrs. Main effects for recovery
time and testing speed in average torque (AvT), peak torque (PT) and
the corresponding angle (Ɵ) were supplemented by regression modelling
to describe the temporal pattern of recovery. A main effect for
isokinetic testing speed was observed in PT and AvT. A main effect for
recovery time highlighted greater strength pre-exercise, with a quadratic
pattern to temporal recovery highlighting minima achieved at
between 40–48 hrs. Strength parameters are not fully recovered until
96 hrs post soccer specific fatigue, with implications for training
design and injury management, particularly within fixture-congested
periods.

The purpose of the study was to investigate the effects of fatigue on lower extremity joint kinematics, and kinetics during repetitive drop jumps. Twelve recreationally active males (n=6) and females (n=6) (nine used for analysis) performed repetitive drop jumps until they could no longer reach 80% of their initial drop jump height. Kinematic and kinetic variables were assessed during the impact phase (100ms) of all jumps. Fatigued landings were performed with increased knee extension, and ankle plantarflexion at initial contact, as well as increased ankle range of motion during the impact phase. Fatigue also resulted in increased peak ankle power absorption and increased energy absorption at the ankle. This was accompanied by an approximately equal reduction in energy absorption at the knee. While the knee extensors were the muscle group primarily responsible for absorbing the impact, individuals compensated for increased knee extension when fatigued by an increased use of the ankle plantarflexors to help absorb the forces during impact. Thus, as fatigue set in and individuals landed with more extended lower extremities, they adopted a landing strategy that shifted a greater burden to the ankle for absorbing the kinetic energy of the impact.

Injury prevention frameworks are critical for preventing musculoskeletal injury and improving rehabilitation outcomes. However, their relative successes in translation arguably rely on two interlinked components: 1) the quality of the empirical evidence used to develop the intervention (content), and 2) the effective application of behavior change and motivation principles to optimise participant adherence and engagement (delivery). The purpose of this commentary is to develop an injury prevention and rehabilitation framework using the best available physics-based simulation, biomechanics, and behavior change research. The intervention as a whole is entitled biomechanically-informed training (BIT). While investigators have previously examined the relative merits of different training genres (e.g., plyometric, balance, resistance), what makes BIT novel is that it explicitly targets the biomechanical mechanisms that mitigate musculoskeletal injury risk (i.e., force) in ways that are underpinned by established behavior change principles. The four pillars of BIT refer to focused exercise use, irrespective of the training genre, to improve an individual's: 1) knee flexion dynamics, 2) dynamic trunk control, 3) gastrocnemius muscle strength, and 4) hip muscular strength. We also present experimental data from two independent training studies verifying the efficacy of BIT for the prevention of knee and anterior cruciate ligament (ACL) injury.

H istorically, linear acceleration has been the main parameter by which to measure athletic head injury risk; however, combinations of linear and rotational impact dosage have been widely acknowledged as contributors to head injury. Current standard head injury metrics-the GSI 9 and HIC 35 -are based on resul-tant linear head center of gravity acceleration and cannot be used to quantify rotational injury risk. These injury metrics were developed from laboratory head impact studies conducted decades ago and were correlated to severe skull fracture and brain injury, but not less-severe brain injuries like concussion. As HIC, GSI, and resultant linear head center of gravity acceleration are the most widely used and only currently mandated injury metrics for athletic head-padding impact testing, 1,19,28 little research has been conducted on boxing and mixed martial arts (MMA) padding effects on rotational or combined impact dosage injury risk. Therefore, while boxing and MMA padding may be capable of reducing linear impact dosage (for example, GSI, HIC, linear acceleration, and impact force), the effects of padding on rotationally in-Object. In spite of ample literature pointing to rotational and combined impact dosage being key contributors to head and neck injury, boxing and mixed martial arts (MMA) padding is still designed to primarily reduce cranium linear acceleration. The objects of this study were to quantify preliminary linear and rotational head impact dosage for selected boxing and MMA padding in response to hook punches; compute theoretical skull, brain, and neck injury risk metrics; and statistically compare the protective effect of various glove and head padding conditions.

Adequately shaped femoral plate is critical for the fixation of fracture in the pertrochanteric regions. Lateral aspect of greater trochanter is an important region where the proximal femoral plate anchored. However, little is known regarding the morphology of greater trochanter. The objective of this study was to measure main dimensions of greater trochanter and other regions in the proximal end of the femur to provide an anatomical basis for the design of the proximal femoral plate. Anthropometric data on the proximal femur were performed utilizing three-dimensional computational modeling. Computed tomography images of healthy femurs in 53 women and 47 men were contributed to three-dimensional femur modeling. All data were compared between male and female femora. The results showed that mean values for male group were found to be greater in most of measured femoral dimensions. Oppositely, females demonstrated higher neck-shaft angle on anteroposterior view and femoral anteversion angle. The anthropometric data can be used for the anatomical shape design of femoral plates for osteosynthesis of fractures in the trochanteric regions. A distinct plate design may be necessary to accommodate differences between the genders.

The kinematics and kinetics of head impact due to a standing fall onto a hard surface are summarized. Head injury due to impact from falls represents a significant problem, especially for older individuals. When the head is left unprotected during a fall, the impact severity can be high enough to cause significant injury or even death. To ascertain the range of head impact parameters, the dynamic response was captured for the pedestrian version of the 5th percentile female and 50th percentile male Hybrid III anthropomorphic test dummies as they were dropped from a standing position with different initial postures. Five scenarios of falls were considered including backward falls with/without hip flexion, forward falls with/without knee flexion and lateral falls. The results show that the head impact parameters are dependent on the fall scenario. A wide range of impact parameters was observed in 107 trials. The 95% prediction interval for the peak translational acceleration, peak angular acceleration, peak force, impact translational velocity and peak angular velocity are 146-502 g, 8.8-43.3 krad/s(2), 3.9-24.5 kN, 2.02-7.41 m/s, and 12.9-70.3 rad/s, respectively.

Limited research has been conducted into the effect of load carriage on discomfort and injuries. This study aimed to determine the skeletal discomfort for part-time soldiers who completed a 1-hour field march carrying 24 kg. A postmarch comfort questionnaire was completed by 127 participants, with exercise withdrawals and postmarch injuries also recorded. The foot was subjectively rated as the most uncomfortable skeletal region. Females reported hip discomfort to be significantly greater than males. The military experience of participants had no difference on the mean perceived comfort ratings of any of the measured regions. Finally, only one participant withdrew from the exercise, with no participants reporting a load carriage injury in the 2 to 3 days proceeding the exercise This study concludes that although a 1-hour period of load carriage causes noteworthy discomfort it is not sufficient to result in noncompletion of a military exercise or cause injury.

BACKGROUND:

A better coupling of the occupant to the car seat in the early phase of a frontal or far side impacts using pretensioner systems may reduce the likelihood of the submarining effect or increases the likelihood of seat belt engaging the shoulder, respectively. However, the high belt forces may also increase the risk of upper body injuries to the vehicle occupant (especially in abdominal region). It was hypothesized that human body characteristics, such as body mass index (BMI) influence the biomechanical response and injury outcome to the abdominal regions during static pretensioning deployment tests.

METHODS:

Four postmortem human specimens (PMHS), in a BMI range from 15.6 to 31.2, were positioned in production seats in a normal passenger position and were restrained using a standard three-point belt system. The pretension forces in the belts were generated at two points (retractor and right anchorage) or at all three locations (retractor, left anchorage, and right anchorage). An optical motion capture system and acceleration cubes mounted to the lumbar spine were used to measure the abdomen deformation during testing.

RESULTS:

The normalized deflections of the thorax recorded at the level of fourth rib were under 10% (noninjury level). Two different patterns were observed in the time histories of abdominal penetration rate in the four PMHSs associated with lower and higher BMI. Abdominal injuries (spleen lacerations) were observed only in the two PMHS with highest BMI.

CONCLUSION:

Based on data from this study and similar data from the literature, belt velocity and FmaxCmax were shown to be the best injury predictors for injury risk analysis for Abbreviated Injury Scale 2+ and for Abbreviated Injury Scale 3+ injuries, respectively.

BACKGROUND:

A better coupling of the occupant to the car seat in the early phase of a frontal or far side impacts using pretensioner systems may reduce the likelihood of the submarining effect or increases the likelihood of seat belt engaging the shoulder, respectively. However, the high belt forces may also increase the risk of upper body injuries to the vehicle occupant (especially in abdominal region). It was hypothesized that human body characteristics, such as body mass index (BMI) influence the biomechanical response and injury outcome to the abdominal regions during static pretensioning deployment tests.

METHODS:

Four postmortem human specimens (PMHS), in a BMI range from 15.6 to 31.2, were positioned in production seats in a normal passenger position and were restrained using a standard three-point belt system. The pretension forces in the belts were generated at two points (retractor and right anchorage) or at all three locations (retractor, left anchorage, and right anchorage). An optical motion capture system and acceleration cubes mounted to the lumbar spine were used to measure the abdomen deformation during testing.

RESULTS:

The normalized deflections of the thorax recorded at the level of fourth rib were under 10% (noninjury level). Two different patterns were observed in the time histories of abdominal penetration rate in the four PMHSs associated with lower and higher BMI. Abdominal injuries (spleen lacerations) were observed only in the two PMHS with highest BMI.

CONCLUSION:

Based on data from this study and similar data from the literature, belt velocity and FmaxCmax were shown to be the best injury predictors for injury risk analysis for Abbreviated Injury Scale 2+ and for Abbreviated Injury Scale 3+ injuries, respectively.

This study aimed to develop a 2-dimensional (2D) video screening tool capable of predicting an athlete's peak 3-dimensional (3D) knee moments during unplanned sidestepping. 2D video-based kinematic measures were simultaneously captured with 3D peak knee moments for 30 female field hockey players (15 junior, 15 senior). Intra- and intertester repeatability of 2D kinematic measures was performed. Then, linear regression models were used to model 3D knee moments from 2D kinematic variables utilizing 80% of the sample (n=24). Regression equations were then validated on the remaining 20% of the sample (n=6). Angular 2D measures had good-excellent intra- (ICC=0.936-0.998) and intertester (ICC=0.662-0.949) reliability. Displacement measures had poor-excellent intra- (ICC=0.377-0.539) and inter-tester (ICC=0.219-0.869) reliability. Significant independent predictors of peak knee moments were dynamic knee valgus, knee flexion angle at foot strike, trunk flexion range of motion (ROM), trunk lateral flexion, hip abduction and knee flexion ROM (P<0.05). Regression equations generated from these models effectively predicted peak knee extension, valgus and internal rotation moments (i. e., were not different from measured values P>0.05, ES<0.4) in the 20% subsample. 2D video-based measurements of an athlete's full body kinematics during unplanned sidestepping provide a reliable, specific, sensitive and cost-effective means for screening female team sport athletes.

Existing rigid body dynamics and finite element computer codes do not have adequate databases for manikin neck structures to properly model head/neck system dynamics occurring in crash or ejection testing. This report describes measured static stiffness and dynamic damping and stiffness characteristics of the Hybrid II and Hybrid III manikin necks and uses these data to improve the current manikin neck data sets of the Articulated Total Body (ATB) model and the Head Spine Model (HSM). The Hybrid II and Hybrid III manikin necks are used extensively throughout the automotive industry, the Department of Transportation, and the Department of Defense for safety testing.

The risk of rib fracture significantly increases with age with compounding deleterious effects.  Previous research identifying rib properties has provided useful information for application in car safety.  However, no study to-date has included a comprehensive sample including pediatric and elderly ribs tested in the same repeatable set-up.  The goal of this study is to characterize the differences in rib response across the age spectrum.  Seventy-one excised ribs from 26 individuals were experimentally tested in a custom fixture simulating a dynamic frontal impact. Four strain gages on each rib were used to determine time of failure. Ages ranged from nine to 92 years old, with a mean age of 61 years and with the exception of the 50’s, all age decades are represented.  Effective stiffness (K) was calculated as the slope of the linear portion of the force-deflection curve. Rib pairs were tested at different rates (1.0 and 2.0 m/s) to assess the rate-dependency of stiffness.  Results indicate a significant difference in effective stiffness by age (evaluated by ANOVA, p < 0.001) and no difference by rate within rib pairs (evaluated by paired t-test, p = 0.125).

There is strong evidence linking an athlete's movement technique during sidestepping with anterior cruciate ligament (ACL) injury risk. However, it is unclear how these injurious postures are influenced by prior movement. We aim to describe preparatory trunk and thigh kinematics at toe‐off of the penultimate‐step and flightphase angular momenta, and explore their associations with frontal‐plane risk factors during unplanned sidestepping maneuvers. We analyzed kinematic and kinetic data of 33 male Australian Football players performing unplanned sidestepping tasks (103 trials). Linear mixed models tested for reliable associations between ACL injury risk during weight acceptance of the execution‐step, with preparatory kinematics and angular momenta of the trunk and thigh during the penultimate‐step. Multi‐planar flight‐phase trunk momenta along with hip abduction angle at penultimate‐step toeoff were significantly associated with peak knee valgus moments during the execution‐step (R2 = .21, P < .01). Execution‐step trunk lateral flexion was significantly predicted by frontal and sagittal‐plane preparatory trunk positioning at toe‐off of the penultimate‐step (R2 = .44, P < .01). Multi‐planar flight‐phase trunk momenta as well as multi‐planar trunk and hip positioning at penultimate‐step toe‐off were associated with hip abduction during the execution‐step (R2 = .53, P < .01). Preparatory positioning of the trunk and hip, along with flight‐phase trunk momentum adjusting this positioning are linked to known ACL injury risk factors. We recommend that during the penultimate‐step athletes maintain an upright trunk, as well as minimize frontal‐plane trunk momentum and transverse‐plane trunk momentum toward the sidestep direction to reduce risk of ACL injury during unplanned sidesteps.

Background: In taekwondo (TKD), the incidence of concussion is four times greater than in American gridiron football. Biomechanical studies of concussion in taekwondo are scarce. Research question: To assess the effect of head impact biomechanics as a result of taekwondo kicks. Type of study: Between-groups design. Methods: Two male (22.0±0.0 years, 184±0.0cm, 81.3±1.8 kg) and two female (0.0±2.8 years, 171.0±1.4 cm, 63.0±5.2 kg) elite taekwondo athletes participated in this study. Head linear acceleration (RLA) and head injury criterion (HIC) data were collected from five different head kicks randomly performed five times. A Hybrid II Crash Dummy head (H2D) was instrumented with a tri-axial accelerometer. Results: Significant differences were found between kicks in RLA (eta2=3.8) and HIC (eta2=4.6) in the men and women (RLA, eta2=4.5 and HIC, eta2=4.7). Post-hoc analyses showed differences in RLA between the jump back kick (61.6±31.0 g) and clench axe kick (33.3±11.1 g) in males (ES=0.9). HIC analysis revealed differences between the jump back kick (556.8±679.2) and jump hook kick (191.0±37.2) (ES=0.7) and in head velocity between the turning kick (5.0±0.5 m.s-1) and jump hook kick (3.2±1.3 m.s-1, ES=1.1) in the males. In the females, there was a difference between the jump back (HIC: 236.8±104.3) and clench axe kicks (22.2±11.2) (ES=1.2) and in foot velocity between the turning (15.7±1.2 m.s-1) and clench axe kicks (9.1±2.3 m.s-1) (ES=1.2). Conclusions: Previous research reported RLA values of 67.0 g (HIC=167) in boxing compared to 72.8 g (HIC=667) in TKD. These high magnitudes of injury-related measures highlight the need for the implementation of more safety precautions. Keywords: taekwondo, head injury criterion, acceleration, concussion, kick

Objective: Previous researches on sports injuries primarily focused on specific games or sports or on specific types of injuries. None of them had tried to explore the injury patterns of games and sports altogether. The current study tried to explore the injury patterns of sportspersons over 16 different types of games and sports. Materials and methods: Total of 1008 injury cases (649 male and 369 female, age 21.07±2.78 and 20.81± 3.01 years) between the academic sessions 2008 to 2017 were analysed. Injury data were extracted from the institute injury record book. Apart from age and gender, ' Body site of injury ', ' Types of injury ' and ' Recurring of injury ' were selected as variables for the study. Descriptive statistics, bar and pie diagram were generated using crosstabs function of IBM SPSS. Results: An average 101.80±12.59 injury was reported per year. Footballers were found to be the highest injured sportsperson (19.5%). Injury percentage of male players (63.75%) was higher compared to female (36.25%) counterparts. Lower limb area (45.28%) was found to be the highest affected body site of injury followed by upper limb area (29.47%). Acute injury constituted 50.39% of overall injuries. Most injuries were non-recurring in nature (63.65%). Further different combinations of analysis revealed more insight of injury patterns of sportspersons.

Pelvic obliquity angles were hypothesised to influence mediolateral (ML) foot position estimates during sporting manoeuvres. Pelvic angles and ML foot position estimates during the weight acceptance phase of sidestepping and straight-line running tasks were obtained from 31 amateur Australian Rules Football players using three different kinematic models. ML foot position was calculated: 1) in the global reference frame, 2) in the pelvis reference frame and 3) in the pelvis reference frame following correction for changes in pelvic obliquity. Significant differences in ML foot position were observed between all three models in both task conditions (p < 0.05). Correcting for changes in time varying pelvic obliquity during running and sidestepping tasks is an important modelling consideration for the reliable measurement of ML foot position when investigating injury and/or stability.

Anterior cruciate ligament (ACL) injuries have been shown to place a severe burden on the injured athlete and the Australian health care system. Significant research has been dedicated to injury prevention training programs with limited success in reducing ACL injury rates among heterogeneous athletic populations. A contributing factor to unsuccessful injury prevention programs are low athlete attendance, compliance and/or engagement to the training protocol (Donnelly et al, 2012a). Though lower limb injury rates are high among elite level athletes, injury prevention programs are generally considered to be low priority as coaches have a misguided perception that there is an inverse relationship between prophylactic training and athletic performance (ie. speed/agility, aerobic power, and strength). Recent literature has identified the dynamic strength and control of the hip and trunk during dynamic sporting tasks is of paramount importance for reducing an athlete’s peak knee loading and injury risk in sport (Dempsey et al, 2009; Donnelly et al, 2012b; Weir et al, 2014). The purpose of this study was to show that a biomechanically focused ACL injury prevention training protocol is effective in reducing ACL injury rates, while simultaneously having no negative effect on athletic performance.

We hereby approve the thesis/dissertation of ____________________________________________________ candidate for the ______________________________degree *. (signed) ______________________________________________ (chair of the committee) ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ (date) _______________________