Virtual Poster Session

Welcome to the Virtual Poster Session, a new and powerful tool for networking and information exchange. Here you can share your work, search though the poster library, and start a dialogue with others in your field. Each uploaded poster that pertains to force measurement and testing can currently be used to apply for an academic travel scholarship; please see the Scholarships page for application details and deadlines.

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Name: niamh.whelan

A popular method for measuring initial contact (foot-strike) during running is the force platform. It has been proposed that the foot contact events can be estimated using peak impact related accelerations of the leg using accelerometers. Various studies have been conducted to compare force platform and accelerometer methods in walking and running. The aim of this study was to develop a method for identifying peak impact accelerations in the anterior- posterior axis using the Delsys Trigno System during running and compare this with initial contact via force plates. Seven national and international sprinters completed runs across a force platform with an accelerometer fixed to their shin. The results showed the acceleration of the anterior-posterior axis approximated foot-strike within ±0.017 s of the foot-strike event detected by the force plate.


Listed In: Biomechanics, Gait
Name: bthakkar

INTRODUCTION
Running-related injuries are most often single-sided and are partially attributed to lower limb movement and loading asymmetries. For example, runners with tibial stress fractures demonstrate asymmetry in loading rate. Running is a dynamic athletic event in which runners often engage in both inclined and declined running with the goal of improving conditioning. Symmetry Angle (SA) is a commonly used, robust measure of determining symmetry. The purpose of this study was to compare peak vertical ground reaction force (VGRF) symmetry using the SA during uphill, level and downhill running on an instrumented treadmill.
METHODS
Eleven healthy adults volunteered to participate in this study and running at 2.7 m/s at grades of 0°, 5.74° incline and 5.74° decline were analyzed. SA was computed using the peak VGRF values from both the limbs.
RESULTS AND DISCUSSION
No statistically significant differences in SA were observed between the three running conditions. (p=0.61) The unexpected uniformity in vertical GRF across uphill, level, and downhill running is consistent with the absence of changes in the peak magnitudes of the GRF observed previously. This suggests that neither moderate uphill or downhill running result in increases in peak GRF that may be considered injurious.
CONCLUSIONS
This was the first study that looked at kinetic symmetry using peak GRF in healthy recreational runners during the three running conditions. This study suggested that uphill and downhill running does not contribute to potential differences in interlimb symmetry and could be considered as a safe alternative to level running on a treadmill.


Listed In: Biomechanics, Gait
Name: rlkrup

Calculating and interpreting joint moments using marker position and ground reaction force (GRF) data is a fundamental part of gait biomechanics research. Due to noise in marker positions, these data are low-pass filtered prior to performing inverse dynamics. Traditionally, kinematic data are filtered at low cutoff frequencies (~6 Hz) and kinetic data are filtered at high frequencies (~30-100 Hz). This technique can result in joint moment impact peaks, particularly during high-impact movements. Filtering marker and GRF data at the same cutoff frequency has been suggested to attenuate these impact artefacts. The effect of various filtering approaches on joint moments in walking is unknown. The purpose of this study was to compare the effect of low-pass filtering cutoff frequencies on joint moments during walking. We hypothesized that filtering would not affect peak joint moments during walking due to smaller violations of the rigid body assumption compared to high-impact movements. Kinetic and kinematic data were collected for twenty-four health adults walking at self-selected speed. Marker position and GRF were smoothed using a 4th-order dual-pass Butterworth filter with cutoff frequencies of 6/45 Hz, 6/6 Hz, 10/10 Hz, for markers and GRF, respectively. A one-way repeated measures ANOVA tested for the effect of filter frequency on peak hip and knee joint moments. Peak hip and knee moments were greater when filtered at 10/10 Hz compared to 6/45 Hz. Although there were differences between cutoff frequency conditions, the effect sizes were small, suggesting that the differences are not large enough to have a meaningful effect.


Listed In: Biomechanics
Name: danialkia

As a treatment for end-stage elbow joint arthritis, total elbow replacement (TER) results in joint motions similar to the intact joint; however, bearing wear, excessive deformations and/or early fracture may necessitate early revision of failed implant components.
A finite element model of a TER assembly was developed based on measurements from a Coonrad-Morrey implant (Zimmer, Inc., Warsaw, IN) using nonlinear elasto-plastic UHMWPE material properties and a frictional penalty contact formulation. The loading scenario applied to the model includes a flexion-extension motion, a joint force reaction with variable magnitude and direction and a time varying varus-valgus (VV) moment with a maximum magnitude of 13 N.m, simulating a chair-rise scenario as an extreme loading condition. Model results were compared directly with corresponding experimental data. Experimental wear tests were performed on the abovementioned implants using a VIVO (AMTI, Watertown, MA) six degree-of-freedom (6-DOF) joint motion simulator apparatus. The worn TER bushings were scanned after the test using micro computed tomography (μCT) imaging techniques, and reconstructed as 3D models.
Contact pressure distributions on the humeral and ulnar bushings correlate with the sites of damage as represented by the μCT data and gross observation of clinical retrievals. The results demonstrate UHMWPE bushing damage due to different loading protocols. Numerical results demonstrate strong agreement with experimental data based on the location of deformation and creep on bushings and exhibit promising capabilities for predicting the damage and failure mechanisms of TER implants.


Name: paigelin7

While normalization of gait is a primary goal of early rehabilitation, between limb asymmetries in knee extensor moment can persist 6-24 months later and previous literature assessing gait interventions is limited. The purpose of this study was to assess the influence of subject-specific cadence gait training program on knee loading mechanics following ACLr. Nine individuals completed an 8-week cadence training program (20min, 3x/week; Table1) and nine sex- and surgery-matched individuals served as controls. All eighteen participants received standard physical therapy and were tested at 1 and 3 months post-op. Kinematic and kinetic data were collected during walking at a self-selected speed. Repeated measures ANOVAs were used for comparisons; significance α≤0.05. Main effects of limb and time were observed: knee ROM (kROM;p<0.001;p=0.044;Fig.1) and knee extensor moment (kEXT;p=0.003;p=0.002) in the cadence and control groups, respectively. No main effects of group for kROM (p=0.136) or kEXT (p=0.229) were found. A trend toward a significant group x time x limb interaction was observed in kEXT (p=0.092), but not kROM (p=0.412). Post-hoc analyses of kEXT (Fig.2) revealed a significant time x limb interaction for the cadence group (p=0.053) but not the control group (p=0.884). In the cadence group, the time x limb interaction was driven by a 131% increase in kEXT in the surgical limb versus a 42% increase in the non-surgical limb between T1 and T2. Consistent with previous findings, these pilot data show promising results as the cadence intervention resulted in improvements in sagittal plane knee loading compared to controls.


Name: mevan6

Asymmetries in discrete measures following anterior cruciate ligament reconstruction (ACL-R) during landing have been reported to be risk factors for secondary ACL injuries. Our purpose was to examine the impact of functional brace wear on kinematic and kinetic inter-limb movement symmetry during landing in ACL-R patients. 20 adolescent athletes (15.8 ± 1.2 years) (7 male, 13 female) 6 months following ACL reconstruction performed 5 trials of a stop-jump task in both a braced (B) and non-braced (NB) condition, with the first landing being analyzed. A custom fit functional knee brace (DJO, Vista, CA) was worn on the ACL reconstructed limb (AL) during the B trials. Mean curves were created for each limb (AL and unaffected limb (UL)) for the vertical (vGRF) and anterior-posterior ground reaction forces (apGRF) and frontal and sagittal knee angles and moments. Coefficients of multiple determination (CMD) between the AL and UL curves were compared between B and NB conditions with students’ t-tests (p≤0.05). No significant differences existed for movement and loading symmetry between B and NB conditions among all subjects. Secondary analysis revealed significant differences in apGRF (p=0.014), vGRF (p=0.011) and sagittal knee angles (p=0.003) in subjects with improved sagittal knee angle symmetry in the B condition. The data show that brace wear improves loading symmetry in adolescent patients that also exhibit improved sagittal knee angle symmetry while braced 6 months following ACL-R. Identifying factors that affect inter-limb movement and loading response to brace wear could assist in determining each patient’s need for a brace.


Name: kbsmale

Since OpenSim uses motion capture data as input while solving inverse kinematic (IK), it is subjected to soft tissue artifact (STA) as the commonly used surface markers do not correctly represent the underlying rigid bones. The purpose of this study was to determine the effect of applying bone pin (BP) marker defined ranges of knee motion in OpenSim IK solutions. Participants completed successful jump lunges where they were asked to stand on their non-test limb and jump forward onto a force plate (AMTI OR 6-7-OP), land on their test limb and maintain balance for two seconds. Data were processed through OpenSim with generic knee joint constraints as well as constraints derived from BP kinematic data.

BP constrained results yielded a significantly more flexed, adducted and externally rotated knee. Significant differences were also observed for anterior/ posterior and distraction/ compression translations throughout the entire jump lunge while medial/lateral translations were only significant pre and 50 ms post contact. After contact, BP constraints produced a significantly greater flexor, abductor, and external rotator moment. With respect to translation forces, the BP solutions produced smaller posterior shear and greater medial shear and compressive forces at the knee joint.

Generic models available in the OpenSim repository contain knee joint ranges that are not physiologically realistic. Therefore, caution should be expressed when using the results from musculoskeletal modelling as STA and optimizations can introduce error in both the kinematics and kinetic solutions. This error is amplified during ballistic and high impact tasks such as jump landing.


Name: robin.healy

Accelerometers have become extremely popular in the measurement of stride frequency as well as other related stride variables with current sensors capable of recording both accelerations and electromyography. The purpose of this preliminary investigation was to assess the estimation of stride frequency during running using a single tri-axial accelerometer compared to a commonly used infrared device the OptojumpTM system. Five healthy participants wore a Delsys Trigno tri-axial accelerometer attached to the right anterior shin and participants repeatedly ran at a submaximal pace through a four metre section of OptojumpTM. Stride frequency was calculated as stride time divided by one. For the OptojumpTM, stride time was the sum of contact and flight times from two consecutive steps. For the accelerometer, stride time was calculated as the time between two consecutive foot contacts on the right side. Foot contact was identified by local maxima in the Y (medial-lateral) acceleration trace. Estimates of stride frequency were compared using paired samples t- tests, intraclass correlation coefficients (ICCs) and Bland and Altman 95% limits of agreement (LOA) with significance set at p < 0.05. The mean difference between estimates was 0.01 Hz (95% LOA: -0.05-0.07 Hz) with single and average ICCs for stride frequency of 0.93 and 0.96 respectively. The results suggest that an accelerometer attached to the shin can accurately estimate stride frequency in running. Discrepancies in stride frequencies can be partially explained by differences in device sampling rates i.e. 137.15 Hz versus 1,000 Hz


Name: sson2

Gait Mechanics Depend Upon Quadriceps Central Activation Ratio in an Anterior Knee Pain Cohort
Son SJ*, Kim HS†, Wiseman B‡, Seeley MK*, Hopkins JT*: *Brigham Young University, Provo, UT, †West Chester University, West Chester, PA, ‡West Virginia University, Morgantown, WV.

Context: Quadriceps deficits are often present in an anterior knee pain (AKP) population. However, common self-reported classification tools including Visual Analog Scale (VAS), Kujala Anterior Knee Pain (KAKP), Tampa Scale for Kinesiophobia (TSK), Tegner Activity Level (TAL) scores, and/or other subject inclusion criteria may not be sensitive enough to identify specific movement characteristics in patients with AKP. Quadriceps central activation ratio (CAR) may help to discriminate movement characteristics in patients with AKP. Objective: To examine gait mechanics between two subdivisions of AKP patients, separated by quadriceps function (CAR < 0.95 and CAR > 0.95). AKP patients were defined by VAS, KAKP, TSK, and TAL scores. Design: Cohort. Setting: Controlled laboratory. Patients or Other Participants: 30 (M=16, F=14; 22.3±3 yrs, 175±9 cm, 72.5±14 kg) AKP patients participated: 15 Quadriceps Deficit (QD: CAR = 0.91±0.04, VAS = 3.87±1.3, KAKP = 82.9±6.6, TSK = 37.9±4.7, TAL = 6.3±1.2) and 15 Quadriceps Functional (QF: CAR = 0.97±0.01, VAS = 3.93±0.7, KAKP = 79.3±7.9, TSK = 36.9±5.2, TAL = 6.8±1.4). Interventions: Subjects performed three quadriceps maximum voluntary contractions (MVC) for 3 sec on a Biodex dynamometer (100 Hz). When MVC torque plateaued 1.5-2 sec later, a superimposed burst was transmitted to two electrodes placed on their quadriceps to measure CAR. Two successful trials were averaged for data analysis. Subjects performed five gait trials at a self-selected walking speed. Gait data were collected using high-speed video (240 Hz) and a force plate (1200 Hz). A functional analysis was used to detect mean between-group differences in gait mechanics during the entire stance phase (0-17% = loading response, 18-50% = mid-stance, 51-83% = terminal stance, and 84-100% = pre-swing). This analysis allowed us to compare variables as polynomial functions rather than discrete values. If 95% confidence intervals did not overlap zero, significant differences existed between groups (p < 0.05). Main Outcome Measures: Sagittal-plane knee joint angle (˚), internal knee joint torque (N∙m), and vertical ground reaction force (VGRF; N/kg). Results: Relative to QF patients, QD patients demonstrated (i) decreased knee flexion angle at 4-90% of stance, (ii) reduced internal knee extension torque at 14-32% of stance, and (iii) reduced VGRF at 19-37% of stance and increased VGRF at 46-70% of stance (p < 0.05). Conclusions: The present data suggest that relative to QF patients, QD patients adopt quadriceps weakness gait mechanics that have been reported in individuals with knee osteoarthritis, ACL reconstruction, and effused knee joints. These alterations may create long-term compensatory gait patterns at the knee and adjacent ankle and hip joints, which may lead to mechanical and biological changes in knee articular cartilage. Future research is needed to examine a potential relationship between these gait alterations and articular cartilage health over the long-term.


Listed In: Biomechanics, Gait
Name: cbutowicz

The purpose of this study was to determine differences in core stability between collegiate football players with and without non-traumatic shoulder pain. 20 collegiate football players completed tests of trunk control and muscle capacity. Control was assessed via an unstable chair placed on a force plate. Static control was assessed by center of pressure movement during seated balance using 95% confidence ellipse area (CEA; mm2) and mean velocity (MVEL; mm/s). Dynamic control was assessed during a speed and accuracy target acquisition task. Directional control (DC; mm; COP path to target) and precision control (movement around target prior to acquisition (PC; CEA mm2)) were measured. Capacity was assessed by trunk flexor (FLEX; s) and extensor endurance (EXT; s) and double-leg lowering (DLL; °). MANOVA (Eta) and t-tests (Cohen’s d) assessed group differences (p < 0.05) Core stability was not significantly different between groups. Data presented as mean ± stdev (No Pain/Pain), p-value, effect size: Static control- CEA 183 ± 129/ 131 ± 85 and MVEL 5.7 ± 3.0/6.4 ± 2.6, p = 0.38, Eta =.33; Dynamic Control- DC 49± 9/46 ± 6, p = 0.49, d =.39 and PC 143 ± 72/93± 25, p = 0.051, d = 0.93; Capacity: FLEX 77 ± 38/99 ± 32, EXT 74 ± 22/69± 28, p = 0.22, Eta= .40 and DLLT 14 ± 10/15 ± 11, p = 0.92, d =.05. Our data do not provide evidence of diminished core stability in football players with shoulder pain.