Lower Extremity Posture Research Articles

Driver’s instinctive response and it’s influence of lower extremity injury

Instinctive response was produced for protecting drivers from injury when facing incoming collisions. For better understanding it’s influence of lower extremity injury, this study proposed an approach to analyze the collision injury considering the instinctive response posture and musculoskeletal characteristics. 20 male drivers were recruited for an instinctive response test in driving simulator and their lower extremity postures and muscle activation of 8 major ones at the collision moment were collected. The difference between different postures and muscles were analyzed and their influence on injuries were investigated by collision simulation. Results showed that increased possibility for the right leg holding on the air or even on the accelerator pedal with increased emergency level at the collision moment. Significant difference existed in different muscles between different postures. The introduction of instinctive response changed the driving posture and musculoskeletal characteristics, which further influence the lower extremity injury. This study help understanding the accurate behavioral and injury procedure and providing support for design a better restraint systems.

Effect of body mass index on plantar pressure distribution in children during standing

Background: Standing plantar pressure measurement can help in tracing the correlation between plantar pressure distribution and lower-extremity posture, altogether with its relationship with BMI in children. The goal of this study is to figure out if BMI affects peak and average plantar pressure distribution in children when standing or not. Study Design: The current study is a primary, observational, cross-sectional one conducted in the Egyptian elementary schools in Talhka City, Dakahlia Governorate. Subjects & Methods: Ninety children; 47 girls and 43 boys with ages ranging between 6 to 12 years old were engaged in this study. The BMI of the study group highlighted the idea that 40% of the children were of normal weight (36 participants), 16.7% were overweight (15 participants), (7.8%) were obese (7 participants), and 35.6% were underweight (32 participants). All statistical measures were carried out using the statistical program for social sciences (SPSS) with version 22 for Windows (IBM SPSS, Chicago, IL, USA). Results: The current research suggests that there was substantial variance in both peak and average plantar pressure of both the right and left feet when standing in various cases with a spectrum of BMIs.

The Effect of Myofascial Exercises on Corrective Exercise Planning of Lower Extremity Posture Disorder Exercises

The Effect of Myofascial Exercises on Corrective Exercise Planning of Lower Extremity Posture Disorder Exercises

Forefoot Injuries in Athletes: Integration of the Movement System.

Despite the prevalence of forefoot related problems in athletes, there are few comprehensive summaries on examination and intervention strategies for those with forefoot related symptoms. While many factors may contribute to pathology and injury, the presence of abnormal foot alignment can negatively affect lower extremity biomechanics and be associated with injuries. Physical therapists may use the characteristics associated abnormal pronation or abnormal supination to describe the movement system disorder and serve as a guide for evaluating and managing athletes with forefoot pathologies. Athletes with an abnormal pronation movement system diagnosis typically demonstrate foot hypermobility, have decreased strength of the tibialis posterior muscle, and present with a medially rotated lower extremity position. Athletes with abnormal supination movement system diagnosis typically demonstrate foot hypomobility, decreased strength of the fibularis muscles, and a laterally rotated lower extremity position. Interventions of manual therapy, taping, strengthening exercises, and neuromuscular reeducation can be directed at the identified impairments and abnormal movements. The purpose of this clinical commentary is to integrate a movement system approach in pathoanatomical, evaluation, and intervention considerations for athletes with common forefoot pathologies, including stress fractures, metatarsalgia, neuroma, turf toe, and sesamoiditis. By applying a prioritized, objective problem list and movement system diagnosis, emphasis is shifted from a pathoanatomical diagnosis-based treatment plan to a more impairment and movement focused treatment.Level of Evidence5

Factors Associated With the Mechanism of ACL Tears in the National Football League: A Video-Based Analysis.

Background:The factors associated with anterior cruciate ligament (ACL) injury mechanism in professional American football players are not well-understood.Hypothesis:It was hypothesized that football-related and player-specific factors, such as position and body mass index (BMI), are associated with ACL injury mechanism in these athletes.Study Design:Descriptive epidemiology study.Methods:Videos of ACL tears occurring in National Football League (NFL) games over 6 consecutive seasons from 2014 to 2019 were reviewed by 2 orthopaedic surgeons who specialize in sports medicine. For each injury, the role of contact (direct contact [contact to the injured knee/lower extremity], indirect contact [contact not involving the injured knee/lower extremity], or no contact) as well as playing situation and lower extremity position were recorded. Additional player characteristics, timing of injury, and surface information were obtained from NFL game-day and injury database statistics.Results:Of the 140 ACL tears, a minority occurred via direct contact to the injured lower extremity (30%), although this varied by position. Just over two-thirds (70%) of ACL tears in offensive linemen occurred via direct contact to the injured lower extremity, while wide receivers had no direct contact ACL tears. Elevated BMI was associated with a greater likelihood of ACL tears occurring via direct contact (53% in players with BMI ≥35 kg/m2 vs 24% in players with BMI <35 kg/m2; P = <.01). Rookies had the lowest percentage of direct contact ACL tears (18%; P = .22). ACL tears that occurred during the middle 8 weeks of the regular season resulted more often from direct contact (38%; P = .06). ACL tears that occurred in the third quarter were the most likely to occur via direct contact (44%), while those that occurred in the fourth quarter were the least likely to occur via direct contact (13%; P < .01).Conclusion:Although most NFL players sustained ACL tears via a noncontact mechanism (ie, through indirect or no contact), players with an elevated BMI, especially on the offensive line, were more likely to injure their ACL through direct contact. Position-dependent variance in injury mechanism may help guide injury prevention efforts in these athletes.

Understanding sagittal compensation in adult spinal deformity patients: relationship between pelvic tilt and lower-extremity position.

In adult spinal deformity (ASD), quantifying preoperative lower-extremity (LE) compensation is important in formulating an operative plan to achieve optimal global sagittal alignment. Whole-body radiographs are not always available. This study evaluated the possibility of estimating LE compensation without whole-body radiographs. In total, 200 consecutive ASD patients with full-body radiographic assessment were categorized into the following three groups according to their cranio-hip balance (distance from the cranial sagittal vertical axis to the hip axis [CrSVA-H]): group 1, anterior-shift (A-shift) group (CrSVA-H > 40 mm); group 2, balanced group, -40 mm < CrSVA-H < 40 mm; and group 3, posterior-shift (P-shift) group, CrSVA-H < -40 mm. After analyzing the correlation between CrSVA-H, pelvic tilt (PT), and LE parameters, the cutoff PT and PT/pelvic incidence (PI) values that correlated with the presence of LE compensation were determined. Previously published data from asymptomatic volunteers were used as a baseline threshold (sacrofemoral angle [SFA] > 217.0° and knee flexion angle [KA] > 11.0°). Among the hip, knee, and ankle, only KA showed a significant increase in the A-shift group compared to the other two groups (p < 0.01). With a wide threshold (SFA > 208.0° and KA > 5.0°), 84.9% of the A-shift group showed LE compensation (hip or knee or both), which was a significantly greater percentage than those in the balanced and P-shift groups (48.4% and 51.9%, p < 0.01). With a narrow threshold (SFA > 217.0° and KA > 11.0°), 62.2% of the A-shift group showed any LE compensation, which was also a higher percentage than the other two groups. The CrSVA-H was moderately correlated with KA (r = 0.502), but had no correlation with PT, SFA, and ankle dorsiflexion angle (AA). PT showed a moderate/strong correlation with SFA, KA, and AA (r = 0.846, 0.624, and 0.622, respectively). With receiver operating characteristic curves, the authors determined that a 23.0° PT with PT/PI > 0.46 predicts the presence of any type of LE compensation with use of the wide threshold. ASD patients with increased CrSVA-H, which represents cranio-hip anterior imbalance, demonstrated a higher prevalence of LE compensation, especially knee flexion, compared to those with neutral and posterior shift of CrSVA. PT represents the extent of LE compensation in patients with spinal sagittal malalignment. Using the cutoff value of PT determined in this study, surgeons can preoperatively estimate the extent of LE compensation without obtaining a full-body radiograph.

Significance of Lower Body Postures in Chair Design.

This study examined a system-level perspective to investigate the changes in the whole trunk and head postures while sitting with various lower extremity postures. Sitting biomechanics has focused mainly on the lumbar region only, whereas the anatomy literature has suggested various links from the head and lower extremity. Seventeen male participants were seated in six lower extremity postures, and the trunk kinematics and muscle activity measures were captured for 5 s. Changes in the trunk-thigh angle and the knee angle affected the trunk and head postures and muscle recruitment patterns significantly, indicating significant interactions between the lower extremity and trunk while sitting. Specifically, the larger trunk-thigh angle (T135°) showed more neutral lumbar lordosis (4.0° on average), smaller pelvic flexion (1.8°), smaller head flexion (3.3°), and a less rounded shoulder (1.7°) than the smaller one (T90°). The smaller knee angle (K45°) revealed a more neutral lumbar lordosis (6.9°), smaller pelvic flexion (9.2°), smaller head flexion (2.6°), and less rounded shoulder (2.4°) than the larger condition (K180°). The more neutral posture suggested by the kinematic measures confirmed significantly less muscular recruitment in the trunk extensors, except for a significant antagonistic co-contraction. The lower and upper back postures were more neutral, and back muscle recruitment was lower with a larger trunk-thigh angle and a smaller knee angle, but at the cost of antagonistic co-contraction. The costs and benefits of each lower extremity posture can be used to design an ergonomic chair and develop an improved sitting strategy.

Post-Trial Feedback Alters Landing Performance in Adolescent Female Athletes Using a Portable Feedback System

BackgroundPost-performance verbal and visual feedback based on data collected via lab-based instruments have been shown to improve landing patterns related to non-contact ACL injury. Biomechanical methods are often complex, difficult to transport and utilize in field settings, and costly, which limits their use for injury prevention. Developing systems that can readily provide feedback outside of the lab setting may support large scale use of feedback training for ACL injury prevention.Purpose/HypothesisThe purpose of this study was to investigate the effectiveness of a single training session using a custom portable feedback training system that provides performance cues to promote changes in impact kinetics and lower extremity position during landing in female athletes.Study DesignRepeated measuresMethodsOne hundred fifty female athletes (ages 13-18 years old) landed from a 50 cm platform with and without feedback related to vertical ground reaction force (vGRF), vGRF symmetry and lower extremity position. Feedback was provided via a portable, low-cost system that included two custom-built force plates interfaced with a digital camera. Each athlete performed six pre-test trials followed by two blocks of six trials where they received visual feedback from the training system and individualized verbal cues from an investigator. Following training blocks, athletes completed six post-test trials without feedback and then six dual-task trials where a ball was randomly thrown to the performer during the landing (transfer task). vGRF and knee to ankle (K:A) separation ratio were measured and the average responses were reported for each trial block.ResultsDifferences in vGRF between baseline, post-test and transfer task trial blocks were observed (F(2,298)=181.68, p < .0001). Mean (SD) peak vGRF (body weight) were 4.43 (0.90), 3.28 (0.61), and 3.80 (0.92), respectively. Differences in K:A ratio between baseline, post-test and transfer task trial blocks were shown (F(2,298)=68.47, p < .0001). Mean (SD) K:A ratio were 0.87 (0.21), 0.98 (0.19), and 0.92 (0.19), respectively.ConclusionA portable feedback system may be effective in reducing peak vGRFs and promoting a more desirable K:A ratio during landing and transfer task landing in adolescent female athletes.Level of Evidence3b

Feasibility of Augmenting Ankle Exoskeleton Walking Performance With Step Length Biofeedback in Individuals With Cerebral Palsy.

Most people with cerebral palsy (CP) suffer from impaired walking ability and pathological gait patterns. Seeking to improve the effectiveness of gait training in this patient population, this study developed and assessed the feasibility of a real-time biofeedback mechanism to augment untethered ankle exoskeleton-assisted walking performance in individuals with CP. We selected step length as a clinically-relevant gait performance target and utilized a visual interface with live performance scores. An adaptive ankle exoskeleton control algorithm provided assistance proportional to the real-time ankle moment. We assessed lower-extremity gait mechanics and muscle activity in seven ambulatory individuals with CP as they walked with adaptive ankle assistance alone and with ankle assistance plus step-length biofeedback. We achieved our technical validation goal by demonstrating a strong correlation between estimated step length and real step length (R = 0.771, p < 0.001). We achieved our clinical feasibility goal by demonstrating that biofeedback-plus-assistance resulted in a 14% increase in step length relative to baseline (p ≤ 0.05), while no difference in step length was observed for assistance alone. Additionally, we observed near immediate improvements in lower-extremity posture, moments, and positive power relative to baseline for biofeedback-plus-assistance (p < 0.05), with none, or more-limited improvements observed for assistance alone. Our findings suggest that providing real-time biofeedback and using step length as the target can be effective for increasing the rate at which individuals with CP improve their gait mechanics when walking with wearable ankle assistance.

Late Stabilization of Developmental Dysplasia of the Hip Without Treatment

Case Approximately three-quarters of neonates with unstable hips will spontaneously stabilize without treatment in the first few weeks of life. This report presents the long-term follow-up of an infant with developmental dysplasia of the hips that stabilized at an older age and without any orthopaedic treatment. Conclusions Factors contributing to the spontaneous stabilization in this case included the patient's self-selected lower extremity position of comfort with hips flexed, abducted, and externally rotated; her delayed walking; and her light body weight.

Serratus Anterior and Upper Trapezius Electromyographic Analysis of the Push-Up Plus Exercise: A Systematic Review and Meta-Analysis.

Whereas the serratus anterior (SA) and the upper trapezius (UT) work as a force couple for scapular motion, weakness of the SA and overactivation of the UT are often present in overhead athletes with shoulder dysfunction. Therefore, researchers addressing an intramuscular imbalance between the SA and UT have focused on finding exercises that target the weak SA and minimally activate the UT. To compare the effectiveness of push-up plus (PUP) exercise variants based on the electromyographic (EMG) activity of the SA and UT. A systematic search of PubMed and Scopus between January 1, 2000, and March 31, 2008. Studies of PUP exercises that involved EMG analysis. We assessed study quality using the Critical Appraisal Skills Program. For the systematic analysis, the following data were extracted: (1) author, year, and study design; (2) participant characteristics; (3) type of PUP intervention; (4) EMG outcome measures; and (5) main results. For the meta-analysis, the EMG data of the SA and UT were calculated using the mean difference of EMG activity with a 95% confidence interval. Based on 19 studies with 356 participants, different hand positions (the distance between the hands, shoulder-flexion angle, and elbow-flexion angle) and different lower extremity positions variably affected the activation of the SA and UT during the PUP exercise. Also, when participants performed the PUP on an unstable surface compared with a stable surface, UT activity increased 2.74% (95% confidence interval = 0.07%, 5.41%). The standard PUP exercise elicited high EMG activity of the SA. Participants generated higher SA and lower UT EMG activity when they performed the PUP exercise on a stable surface in full elbow extension, with the hands placed shoulder-width apart, shoulder-flexion angles of 110° or 120°, and the ipsilateral lower extremity lifted.

Predicting Ambulatory Function Based on Infantile Lower Extremity Posture Types in Amyoplasia Arthrogryposis.

Arthrogryposis multiplex congenita (AMC) is a nonprogressive syndrome with multiple rigid joints, fibrotic periarticular tissue, and muscular fibrosis. The most common subgroup is amyoplasia. Ambulation is one of the most significant functions of the lower extremities as it translates to increased functionality and independence in adulthood. There is no predicative scale to determine ambulation at maturity for the infant with amyoplasia. It is believed lower extremity resting position of infants with amyoplasia potentially correlates with ambulation at maturity. The purpose of this study was to classify the infantile position of lower extremities and muscle strength to predict ambulation potential at maturity. Children with amyoplasia were retrospectively reviewed and classified into groups based on infantile position of hip-knee alignment and limb muscle function. Sitting, standing, and walking skills from infancy into adulthood were evaluated. The ambulation function was correlated with the infantile position of the lower extremities. Amyoplasia cases were sorted into 5 types and correlated with ambulatory potential. Type I: mild ambulatory impairment with infantile position of flexed knees and hips but full range of motion. At maturity, all were community ambulators. Type II: moderate ambulatory impairment having infantile position of hip flexion, hip external rotation, and knee flexion contractures. Hip abductors and external rotators had antigravity strength. All stood and walked during the first decade of life with knee ankle foot orthoses. Type III: severe ambulatory impairment having infantile position of hip flexion, abduction, external rotation, and knee flexion contractures but lacked hip muscle recruitment. All used wheelchairs at maturity. Type IV: mild ambulatory impairment with infantile position of extended knees and flexed dislocated hips. At maturity, 90% were community ambulators. Type V: variable ambulatory impairment having asymmetric hip and knee alignment with unilateral hip dysplasia with extended knee and opposite limb flexed. Ambulation skill varied at maturity with 27% full-time wheelchair users. Amyoplasia can be sorted by infantile position of lower extremities and muscle strength into 5 types to predict ambulatory function. Level III-Prognostic Study.

Lower Extremity Position Test: A new clinical quantitative assessment tool of proprioception post stroke.

To develop a quantitative, inexpensive and easy to use tool, for assessing proprioception of the lower extremity of individuals post-stroke, and examine its test-retest reliability and known-groups validity. The Lower Extremity Position Test was developed. Testing procedure: seated subjects were asked to reproduce 12 cm or 22 cm distances on a plastic surface, by verbally stopping passive movement of the foot produced by the tester. The deviation from the target point was measured as the mismatch score. Fifty one subjects post-stroke (n = 51) participated in prospective test-retest assessment. The tests were performed one week apart by a single assessor, in physical therapy out-patient clinics. The t-test, ICC and Bland-Altman tests were used to determine known-groups validity by determining leg differences and test-retest reliability. Post-stroke involved foot demonstrated significantly higher mismatch scores then the uninvolved foot did (p < 0.0001). Good test-retest reliability was demonstrated for the involved leg for both 12 cm and 22 cm distances (ICC = 0.79 and 0.85, respectively). The 95% repeatability ranges were leg related. The Lower Extremity Position Test (LEPT) is a newly-developed testing tool with good clinical utility, reliable in post-stroke population and has known-group validity (involved versus uninvolved foot).

Anatomical distribution and change of distal deep venous thrombosis in patients with hip fracture

Objective To investigate the anatomical distribution and change of distal deep venous thrombosis in patients with hip fracture, to provide evidence for prevention and treatment of deep vein thrombosis in patients with hip fracture and lower limb deep vein ultrasound examinatio. Methods The clinical data of 383 patients with hip fractures who were admitted in Department of Orthopaedics Trauma, Xi′an Jiaotong University Medical College Red Cross Hospital from July 2014 to April 2018 were analyzed retrospectively. There were 122 males and 261 females, the age range was 17 to 94 years, the median was 78 years, and the interquartile range was 12 years. There were 154 cases of femoral neck fracture, 208 cases of femoral intertrochanteric fracture, and 21 cases of femoral subtrochanteric fracture. Deep venous thrombosis was assessed by ultrasonography before and 3-5 days after operation, and the anatomical location and changes of deep vein thrombosis were analyzed. The skewed distribution data were represented by the median and interquartile range. The proportion of the number of deep venous thrombosis case in the anatomical position of the lower extremities was expressed as a percentage. Results Of the 383 patients with hip fracture who had distal deep venous thrombosis before surgery, isolated distal deep vein thrombosis (IDDVT) accounted for 89.30% (342/383), and multivessel thrombosis accounted for 10.70% (41/383). In IDDVT, intermuscular venous thrombosis was the most common, and no anterior venous thrombosis occurred. In multivessel thrombosis, two or three of the intermuscular vein, the posterior tibial vein, and the iliac vein were more common. Twenty-eight (7.31%) patients had distal thrombus extension to the proximal end (including 21 cases involving the iliac vein and 7 cases involving the superficial femoral vein), IDDVT accounted for 61.88% (237/383). The involvement of multiple venous thrombosis accounted for 16.19% (62/383), 62.40%(239/383) of the distal thrombus position did not change, and 14.62%(56/383) of the distal thrombus disappeared. Conclusions For patients with hip fracture, the intermuscular vein is the most common site of distal deep venous thrombosis, ultrasound examination of anterior tibial vein is not necessary. Under anticoagulation, 7.31% of distal deep venous thrombosis may extend to the proximal and 14.62% of distal deep venous thrombosis disappear. For patients with hip fracture complicated with distal deep venous thrombosis in hospital, patients without contraindication of anticoagulation should be treated with anticoagulation at an early stage to prevent the proximal progression or fall off of thrombosis and reduce the risk of distal deep venous thrombosis. Key words: Hip; Venous thrombosis; Dissection

Epidemiology and Video Analysis of Achilles Tendon Ruptures in the National Basketball Association

Background: There is a paucity of literature regarding risk factors and mechanisms of Achilles tendon (AT) ruptures in the National Basketball Association (NBA). Purpose: To identify the risk factors and outcomes of AT ruptures in NBA athletes. Furthermore, using video analysis, to characterize the mechanisms of rupture by identifying the most common playing situations and lower extremity positions at the time of injury. Study Design: Descriptive epidemiology study. Methods: AT ruptures in the NBA that occurred between the seasons of 1969-1970 and 2017-2018 were identified. Player data collected included age, position, body mass index, total games started before and after injury, and Player Efficiency Rating. Injury-related variables collected included date of injury, laterality, minutes played before injury, operative versus nonoperative treatment, and time to return to play. Available video footage was analyzed for the mechanism and body position at the time of injury. Univariable and multivariable linear regression was used to compare changes in performance before and after AT rupture. Statistical significance was set at P < .05. Results: Forty-four ruptures were identified between 1970 and 2018. The mean age was 28.3 years, with players averaging 6.8 seasons before AT rupture. AT ruptures were most prevalent during early-season game play (27.3%), followed by preseason (18.2%) and late season (18.2%). More than a third (36.8%) of players either did not return to play or started in fewer than 10 games in the remainder of their career, with 21% of ruptures leading to retirement. The mean time to return to play was 10.5 months. The Player Efficiency Rating declined by an average of 2.9 points (range, –11.5 to +2.3) (P < .001). Analysis of available injury footage (n = 12) demonstrated all ruptures to be noncontact in nature, most commonly occurring just before takeoff as the player began to push off from a stopped position, with the foot in dorsiflexion, the knee in early flexion, and the hip in extension. Conclusion: In the NBA, a majority of AT ruptures occur early in the season, in veteran players, with almost half not returning to play or starting fewer than 10 games in the remainder of their career. The most common mechanism of injury is taking off from a stopped position just before toe-off in a dorsiflexed foot.

Lower Extremity Position Test: A Simple Quantitative Proprioception Assessment

Proprioception is the sense that enables to perceive the body’s movement and position, and permits smooth and coordinated motor performance.

2-8 Yaş Arası Çocuklarda Kuadriseps Açısının Değerlendirilmesi

Aim The quadriceps angle is the angle between the line drawn from the spina iliaca anterior superior to the midpoint of the patella, and the line drawn from the midpoint of the patella to the tuberositas tibiae. It is important for lower extremity posture. The aim of this study was to determine the normative quadriceps angle value by measurement, and to assess the probable effect of factors such as measurement position, age, sex, and presence of pes planus on these values. Material and Methods A total of 599 children consisting of 296 (49.4%) girls and 303 (50.6%) boys aged between 2 and 8 years, were included in the study. The children were divided into three groups by age as 2-4 years, 4-6 years, and 6-8-years. After the children's demographic data were collected, the quadriceps angle was measured using an electronic goniometer. Pes planus was assessed by drawing the Feiss line. Results In bilateral measurement, it was found that the quadriceps angle decreased with age both in the supine and standing positions (p 0.05). A low negative correlation was found between body mass index and the quadriceps angle in both measurement positions (p<0.05). Conclusion It was found that positional changes and weight bearing on limbs did not cause any change in knee position in healthy children. We consider that the decrease in quadriceps angle in this age group is due to growth rate asymmetry between the femur shaft and pelvic diameter.

Impact of posture choice on one-handed pull strength variations at low, waist, and overhead pulling heights

Manual exertions with one hand are commonly performed; however, current one-handed normative strength databases note large strength variations not explained by participant demographics, e.g., age and gender. This study models how the postures that participants choose impact their one-handed pull strength. Lower-extremity posture, defined as distance from handle, were measured for 31 participants performing two maximum one-handed frontal pull exertions at three handle heights, resulting in a strength-posture dataset of 186 maximal exertions. Regression models with anthropometric and lower extremity positions were created for each handle height. Smaller distances between the front-foot and handle were associated with higher strength. Larger back-foot distance to handle was positively associated with strength for low and waist-level handle heights. Larger hip distances from the handle increased pull strengths and interacted with feet positions. This study quantifies the relationship between one-handed pull strength with anthropometry and postures and provides practitioners posture-based equations that can be used to estimate safe pull strengths given workplace posture constraints. Relevance to industryMaximum one-handed pull strength models are presented that can assist practitioners in: 1) assessing whether strength demands are within worker's capability in the workplace, 2) designing workplaces that better accommodate the range of postures chosen during maximum exertion, and 3) identify workplace layout constraints that adversely impact strength capabilities.

The Injury Tolerance of the Tibia Under Off-Axis Impact Loading.

During a frontal collision, there are a range of lower extremity postures that the vehicle's occupant may assume, potentially changing the way load is transmitted to this region of the body. While most experimental studies on the tibia's injury tolerance assume that load is directed along the leg's long axis, the effects of off-axis loading due to non-standard postures have not been well quantified, and commonly-cited injury criteria such as the Tibia Index do not directly account for posture. Therefore, twelve cadaveric tibias (paired from six donors) were subjected to off-axis impact loading in a custom-built test apparatus. One specimen from each pair was held at an angle of 15° relative to the direction of loading, while the contralateral was held at an angle of 30°, with these angles representing ankle plantarflexion and corresponding knee extension in a vehicle occupant. Specimens held at 30° fractured at lower forces than the specimens held at 15° (mean force=5.8 vs. 7.5kN). This indicates that posture should be incorporated into injury criteria for the tibia in future safety assessments instead of using a single force value based on axial impacts.

Evaluating the Reliability of a Marker-Less, Digital Video Analysis Approach to Characterize Fire-fighter Trunk and Knee Postures During a Lift Task: A Proof-of-Concept Study

Background: Valid and reliable postural assessment tools can better support injury prevention strategies. 3- dimensional movement analysis as the gold standard to assess human movement is often not feasible in applied, occupational settings. For example, heavy lifting associated with known injury risk factors is impacted when performed by fire-fighters wearing personal protective equipment (PPE). Task simulations including PPE complicate postural assessment methods. Consequently, the study purposes were: a) To establish proof-of-concept using Dartfish movement analysis software to measure fire-fighters’ trunk and knee postures during a fire-fighting lift task while wearing PPE and b) To establish the reliability of this approach. Methods: A sample of twelve active-duty fire-fighters lifted a high-rise pack from floor to shoulder level. Frontal and sagittal trunk and knee flexion angles and hip vertical displacement were measured using Dartfish. All measurements were repeated on a second day for reliability analysis. Descriptive statistics characterized fire-fighter lower extremity postures. Intra-class correlation coefficients, standard error of measurement and minimal detectable change determined reliability of trunk and knee angles and hip displacement measures. Results: Fire-fighters demonstrated 150° ± 12° of left knee flexion, 150° ± 13° of right knee flexion and 98° ± 17° of trunk flexion when lifting a high-rise pack from floor to shoulder level. Hip vertical displacement was 19% ± 8% when normalized to the individual’s height. Absolute reliability results indicated that fire-fighter knee postures could be assessed within 5° and trunk postures within 9° when using Dartfish. Conclusion: Although measurement reliability of trunk and knee angles was comparable to previous studies, accuracy limitations and methodological challenges were identified. Protocol recommendations to optimize reliability and interpretability include focusing on using positional coordinates to identify hip displacement; further research to validate this approach is suggested. Implications include measuring impacts of ergonomic interventions designed to modify fire-fighter task performance strategies in response to known injury risk factors.