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: dyocum

Purpose: An increased likelihood of developing obesity-related knee osteoarthritis may be associated with increased peak internal knee abduction moments. Increases in step width may act to reduce this moment. The purpose of this study was to determine the effects of increased step width on knee biomechanics during stair ascent of healthy-weight and obese participants. Methods: Participants ascended stairs while walking at their preferred speed in two different step width conditions – preferred and wide. A 2 x 2 (group x condition) mixed model analysis of variance (ANOVA) was performed to analyze differences between groups and conditions (p<0.05). Results: Increased step width decreased the loading-response peak vertical ground reaction force (GRF), loading-response knee abduction moment, knee extension ROM, and knee abduction ROM in both groups. However, it also increased loading and push-off peak mediolateral GRF, and peak knee abduction angle in both groups. Obese participants experienced a disproportionate increase in loading and push-off peak mediolateral GRF, and peak knee abduction angle compared to healthy. Conclusion: Increased SW successfully decreased loading-response peak knee abduction moment. Implications of this finding are that increased SW may decrease likelihood of developing medial compartment knee osteoarthritis. This study shows that this gait modification affects obese and healthy-weight differently, and the influence of body mass on knee biomechanics.

Listed In: Biomechanics
Name: mtitch

Anterior cruciate ligament (ACL) tear greatly increases the risk of knee osteoarthritis (OA), even when patients undergo ACL reconstruction surgery (ACLR). Changes to walking kinematics following ACLR have been suggested to play a role in this degenerative path to post-traumatic OA by shifting the location of repetitive joint contact loads that occur during walking to regions of cartilage not conditioned for altered loads. Recent work has shown that changes to the average knee center of rotation during walking (KCOR) between 2 and 4 years after ACLR are associated with long term changes in patient reported outcomes at 8 years. Changes to KCOR result in changes to contact patterns between the femur and the tibial plateau. However, it is unknown if changes to this kinematic measure are reflected by changes to cartilage as early as 2 years after surgery. Ultrashort TE-enhanced T2* (UTE-T2*) mapping has been shown to be sensitive to subsurface changes occurring in deep articular cartilage early after ACL injury and over 2 years after ACLR that were not detectable by standard morphological MRI. Thus, the purpose of this study was to test the hypothesis that side to side differences in KCOR correlate with side to side differences in UTE-T2* quantitative MRI (qMRI) in the central weight bearing regions of the medial and lateral tibial plateaus at 2 years following ACLR.

Thirty-five human participants (18F, Age: 33.8±10.5 yrs, BMI: 24.1±3.3) with a history of unilateral ACL reconstruction (2.19±0.22 yrs post-surgery) and no other history of serious lower limb injury received bilateral examinations on a 3T MRI scanner. UTE-T2* maps were calculated via mono-exponential fitting on a series of T2*-weighted MR images acquired at eight TEs (32μs -16 ms, non-uniform echo spacing) using a radial out 3D cones acquisition. All subjects completed bilateral gait analysis. Medial-lateral (ML) and anterior-posterior (AP) coordinates of average KCOR during stance of walking were calculated for both knees. Side to side differences in KCOR were tested for correlations with side to side differences in mean full thickness UTE-T2* quantitative values in the central weight bearing regions of the medial and lateral tibial plateau using Pearson correlation coefficients.

There was a distribution in UTE-T2* values, with some subjects having higher UTE-T2* and some lower in the ACLR knee relative to the contralateral knee. A significant correlation (R=0.407, p=0.015, Figure 1A) was observed between UTE-T2* and the ML KCOR with a more lateral KCOR corresponding to higher values of UTE-T2* for the medial tibia. Similarly, for the lateral tibia, a lower UTE-T2* was correlated with a more posterior KCOR (R=0.363, p=0.032, Figure 1B). Significant correlations were not observed for UTE-T2* in the lateral tibia with the ML position of KCOR or for UTE-T2* in the medial tibia with the AP position of KCOR.

The results of this study support the hypothesis that side to side differences in mean full thickness UTE-T2* qMRI correlate with side to side differences in knee kinematics at 2 years after ACLR. The finding that a more lateral KCOR in the ACLR knee correlates with UTE T2* values in the medial tibia that were higher than the contralateral side suggests that this kinematic change, which has been previously shown to result in more relative motion between the femur and tibia in the medial compartment, could be affecting subsurface matrix integrity, inducing changes detectable by UTE-T2* mapping. Additionally, the finding that a more posterior KCOR in the ACLR knee correlated with UTE-T2* values in the lateral tibia that were lower than the contralateral knee further suggests that the UTE-T2* metric may reflect early changes in cartilage health. When interpreted within the context of prior work showing that a posterior shift in KCOR from 2 to 4 years post-surgery correlated with improved clinical outcomes at 8 years, the observed lower UTE-T2* with a more posterior KCOR, which is reflective of improved quadriceps recruitment, suggests positive cartilage matrix properties. In spite of the limitations of this cross-sectional and exploratory study, and the difficulty accounting for changes in the contralateral knee, these results support future studies of the relationship between UTE-T2* and KCOR to provide new insight into predicting the risk for OA after ACLR.

Name: kvalenzu

Stair negotiation is one of the more difficult daily activities reported by total knee replacement (TKR) patients. Dissatisfied TKR patients have reported increased difficulty with stair negotiation, however it is unknown what the underlying mechanical issues are for this population. Therefore, the purpose of this research was to examine the knee joint biomechanics of dissatisfied TKR patients during stair descent. Nine dissatisfied TKR patients (34.6±14.3 months from surgery), 15 satisfied TKR patients (29.3±12.8 months from surgery), and 15 healthy participants performed stair descent trials on a five-step instrumented staircase at a preferred gait speed. The dissatisfied group showed lower knee extension and abduction moments in their replaced limb. The 2nd peak vertical ground reaction force (VGRF) and 1st and 2nd peak knee internal rotation moments showed lower moments for replaced limbs compared to non-replaced limbs. First peak VGRF was reduced for dissatisfied group compared to satisfied and healthy groups. The dissatisfied TKR group had significantly increased pain levels on their replaced limb compared to all other groups and limbs. The dissatisfied group had reduced gait speed compared to the satisfied and healthy groups. Increased pain levels lead to reduced descent speed and peak loading-response and pushoff sagittal plane knee joint moments in dissatisfied total knee replacement patients during stair descent. This creates an asymmetry in the extension loading response moment for the dissatisfied group, with the non-replaced limb showing increased joint moments whereas the satisfied and healthy groups do not have that imbalance.

Listed In: Biomechanics
Name: Patrick Carden

Analysis of lower limb biomechanics during jumping and landing tasks are often used to assess lower limb injury risk in research and applied practice within professional team sports. However, there are limited instances of these movements being incorporated into research focusing on Achilles tendinopathy development. PURPOSE: To investigate whether differences existed in lower limb motion and moments during jumping and landing between individuals who develop Achilles tendinopathy and those who remain injury free. METHODS: Male professional Rugby Union players without lower limb injury (n = 43) were compared to players who sustained Achilles tendinopathy (n = 8). Five single-leg drop vertical jumps per leg were performed at the start of their pre-season training. Motion of the lower limbs were recorded synchronously with ground reaction force. RESULTS: Players who sustained Achilles tendinopathy demonstrated significantly increased rear-foot inversion-eversion range of motion (p = 0.03), a reduction in dorsi-plantarflexion range of motion (p = 0.01) and knee flexion-extension range of motion (p = 0.03). Peak dorsiflexion velocity (p = 0.02) and peak knee flexion velocity were also reduced in those with Achilles tendinopathy (p = 0.03). No differences in hip joint kinematics were observed. Controls displayed slightly larger peak plantarflexion moments; however this difference was not statistically significant (p = 0.15, g = 0.60). CONCLUSIONS: The findings indicated that players who subsequently developed Achilles tendinopathy displayed an altered single leg landing strategy when compared to players who did not sustain injury; with motion of the ankle joint and rear-foot most influenced.

Name: lizbell@terpmai...

Objectives: The conventional push-up is a popular exercise used by the American College of Sports Medicine to test participant muscular endurance. Push-ups require changes in the ground reaction forces generated at each point of contact with the ground (all four extremities) which are achieved through muscular contractions. Although this exercise is common, the motor control mechanisms used in this motion are relatively unknown. We investigated whether humans adjust individual limb forces (push-up synergies) as they reached volitional fatigue and evaluated the hypothesis that muscular fatigue influences synergistic actions between the forces produced at the hand contact points. Approach: Twenty-one volunteers participated in a single motion capture trial where they performed as many push-ups as possible, stopping at self-determined failure. Push-ups were completed to a controlled three-beat rhythm (down, up, hold plank) at a rate of 24 repetitions per minute. Participants were instructed to arrange themselves in a plank position with each extremity within the bounds of an embedded force platform and analog data was collected at a frequency of 1000Hz. An index of synergy, defined as correlations between vertical forces, was calculated for every downward and upward motion within the push-up trial. Findings: Between-arm vertical forces were positively correlated during upward and downward motion. Positive correlation indicates that limbs worked together to produce increases or decreases needed for center of mass movement. Upward limb synergy significantly (p ≤ 0.00) decreased as participants neared volitional fatigue while downward limb synergy did not significantly change (p = 0.77). Conclusions: We found that muscular fatigue affected the synergistic actions between limbs in upward motion but not in downward motion. After muscular fatigue, between arm synergy was reduced only during concentric muscle contractions. Public Health Significance: Better understanding the synergistic changes produced by fatigue could be used to evaluate or better understand control changes behind pathologic gait or movement adaptations.

Name: freyjoce

INTRODUCTION. Increased age is associated with changes in gait mechanics and decreased muscle function. As the knee extensors (KE) are prime movers in gait, altered KE function (strength, power, fatigability) could alter knee mechanics. This study aimed to determine whether a bout of exercise induces KE fatigue and changes in knee mechanics in two older groups with different physical activity levels: sedentary adults and runners.

METHODS. Adults aged 55-70 who were either runners (≥15 miles/wk) or sedentary (≤3x30 min exercise bouts/wk) completed gait and strength testing before and after a 30 minute treadmill walk (30MTW). Joint kinematics were calculated using the point cluster technique. Externally-referenced moments were calculated using inverse dynamics. KE power and isometric strength were assessed via isokinetic dynamometry. Changes in KE power and knee mechanics were calculated; within-group changes were examined using paired t-tests (p<0.1).

RESULTS. Sedentary adults displayed a drop in KE power at 6/8 contraction velocities vs. 2/8 in runners (poster Figure 2). Both groups showed an increase in knee flexion angle at heel strike and runners displayed decreased knee flexion moments post-30MTW (poster Figure 3).

CONCLUSIONS. Vigorous physical activity may allow older adults to maintain fatigue resistance. Sensitivity of knee mechanics to KE fatigue remains unclear as few changes were seen even in a fatigued group. Global, rather than discrete, measures of joint function may provide more sensitive measures of the response of gait mechanics to muscle fatigue and may allow for a more complete picture of the impact of muscle function on gait.

Listed In: Biomechanics, Gait
Name: sson2

Purpose: Knee pain is a chief symptom of knee pathology. Both acute and chronic knee pain result in altered joint loads during walking, which potentially result in mechanical and biological changes in knee articular cartilage. Due to confounding factors in clinical knee pain (effusion, muscle weakness, inflammation, structural changes), it is difficult to examine the independent effect of knee pain on walking mechanics. The purpose of this study is to examine whether unilateral experimentally induced knee pain influences bilateral loading patterns during walking in healthy individuals.
Methods: This study was a controlled laboratory, cross-over trial. Each of 30 able-bodied subjects (M = 20, F = 10; 23 ± 2.4 yrs, 71 ± 12.7 kg, 178 ± 8.2 cm) completed three experimental sessions: pain (5.0% NaCl infusion), sham (0.9% NaCl infusion), and control (no infusion) in a counterbalanced order, 2 days apart (a washout period). For the experimental sessions, hypertonic (5% NaCl) or isotonic (0.9% NaCl) saline was continuously infused into the right (involved limb) infrapatellar fat pad using a portable infusion pump, which produced a continuous saline flow of 0.154mL/min (total 2.16 mL) for 14 min for the pain or sham session, respectively. No infusion was administered to the control session. Subjects and investigators were blinded regarding the saline solution which was being infused. During each of three experimental sessions, subjects performed 30-sec gait trials at a self-selected speed at two time points (pre- and post-infusion). Ground reaction force (GRF) data were collected using an AMTI instrumented force-sensing tandem treadmill (1200 Hz). The first 4 successful gait cycles in each limb were used for data analysis. A functional data analysis approach (α = .05) was used to detect time (pre- and post-infusion) x limb (involved vs. uninvolved) interactions for the vertical, anterior-posterior, and medial-lateral GRF.
Results: Significant time x limb interactions were observed during the pain session (hypertonic saline; 5.0% NaCl; p < .05). Experimental knee pain resulted in up to (i) 0.05 N/kg less vertical GRF and 0.02 N/kg more vertical GRF during various stance phases, (ii) 0.01 N/kg less breaking GRF during loading response, and (iii) 0.007 N/kg less lateral GRF and 0.007 N/kg more lateral GRF during various stance phases in the involved limb.
Conclusions: Relative to the pre-infusion condition, subjects during the knee pain condition tended to walk with less vertical, posterior and lateral GRF in the involved limb (painful limb) across various portions of stance, which simultaneously increased loads in the uninvolved limb (non-painful limb). Our data suggest that compensatory loading patterns occur simultaneously for the involved and uninvolved limbs. This unloading pattern in the involved limb may be due to perception of knee pain, which can make subjects feel fear for damaging or provoking pain more during walking. Moreover, voluntary and/or involuntary quadriceps inhibition (e.g., neuromuscular activation and strength) due to experimentally induced knee pain may play a role in reducing the loads in the involved limb because the quadriceps support the center of body mass eccentrically from initial loading response to midstance to prevent collapse of the lower limbs. These asymmetrical loading patterns due to knee pain and associated with neural inhibition may be a risk factor for knee joint disease progression via changes in mechanical components.

Listed In: Biomechanics, Gait
Name: emesserschmidt

Title:  Head Acceleration During Girls Youth Soccer Using Real Time Data
Emily Messerschmidt, Katlyn Van Patten, Ryan Lee, Srikant Vallabhajosula

Purpose/Hypothesis: While the acute effects of concussion have been the focus of research in the past, there is a new emphasis toward following the cumulative effects of sub-concussive head accelerations in athletics. This is especially important in youth athletes because the developing brain is more vulnerable to injury from head trauma in sports like soccer due to techniques such as heading, that can result in numerous head impacts throughout play. There is a current lack of evidence on the magnitude and frequency of head accelerations that occur during real-time youth sports, including soccer, and whether these accelerations have a detrimental cumulative effect. The purpose of the current study was to measure the head acceleration that youth athletes experience during real-time soccer games.
Number of Subjects: 31 under-15 girls club soccer participants. 11 players monitored each game.
Materials/Methods: 3 season games were observed. Triax Smart Impact Monitor headband accelerometers were worn during gameplay to collect real-time head impact data. Forces >10g were recorded. Games were video recorded for further analysis. Head impacts were categorized by type of impact: purposeful header (PH), player to player (PP), player to ground (PG), and ball to head (BH). Data was analyzed using descriptive statistics.
Results: A total of 171 impacts were observed (PH=20, PP=113, PG=36, BH=2). Only one impact recorded was above the concussion threshold of 70g. The majority (77%) of impacts observed were <10g. Of the accelerations recorded, PH resulted in the largest average acceleration (36.8±14.9g) followed by PG (20.5±4.2g), and PP (19.5±4.6g). The maximum accelerations for PH, PG and PP were 73g, 26g and 30g respectively. No BH accelerations were recorded >10g.
Conclusions: While PH yielded the highest average acceleration, it was one of the least frequently occurring impacts. PP impacts were most common however the majority produced little to no head acceleration. While there was variability of head acceleration that occurred within each type of impact, none produced consistently dangerous (≥70g) accelerations.

Clinical Relevance: This study provides preliminary evidence of the impacts sustained during girls youth soccer games for athletic trainers or sports physical therapists who are monitoring athletes for concussions. The findings reveal that the use of headband accelerometers to measure real-time data can be a useful tool to monitor multiple players on the field. There remains a need for further research into the effect of cumulative sub-concussive impacts during soccer in youth athletes with larger sample size. Further studies should investigate the impacts players sustain over multiple seasons to observe if those who experience multiple sub-concussive impacts report concussion-like symptoms or show concussion-like signs. Additionally, this study adds evidence to the existing literature that the use of video analysis to confirm the occurrence of impacts and to correctly categorize them is highly beneficial to ensure reliability in future studies.

Name: Matthias-K

This study examined triceps surae muscle strength and tendon stiffness in young adult elite sprinters and jumpers over one season, in order to detect potential discordance between muscle and tendon adaptation due to training. Furthermore, we examined the effect of habitual training on triceps surae muscle-tendon unit (MTU) mechanical properties in young and older athletes, using a cross-sectional design.
Eleven healthy younger elite sprinters and jumpers, 12 master athletes, 12 recreationally active young controls and one young elite athlete, 10 months after unilateral Achilles tendon reconstruction participated. All young athletes underwent regular measurements over one season. Triceps surae muscle strength and tendon stiffness of both legs were analysed using dynamometry and ultrasonography synchronously.
Within one season, similar patterns of relative changes in muscle strength and tendon stiffness were seen in the young elite athletes. For the tendon reconstruction athlete, the affected leg showed no increases in muscle strength or tendon stiffness over one season, and remarkably lower muscle strength but similar tendon stiffness compared to the non-affected leg. Healthy young elite athletes showed higher muscle strength and tendon stiffness than both other subject groups, with no differences between young controls and master athletes.
Our results provide evidence for training-induced concordant adaptation of muscle and tendon over one season within healthy young elite athletes. Achilles tendon rupture and reconstruction may be a major risk factor for irreversible discordance within the triceps surae MTU. Finally, habitual athletics training over the lifespan may effectively counteract age-related decreases in muscle strength and tendon stiffness.

Name: catelli

INTRODUCTION: Cam femoroacetabular impingement (FAI) is characterized by an osseous overgrowth on the femoral head-neck junction [1], leading to pain and limited range of motion (ROM) during daily life activities [2]. Corrective surgery is highly recommended and performed in order to reduce or eliminate pain and further development of osteoarthritis (OA). However, it is still unclear whether it would lead to improved functional mobility. The purpose was to compare kinematic variables of the operated limb between FAI patients when performing a squat task pre-surgery and at around 2-year follow-up. A secondary objective consisted of express the results in a biomechanical functional score to quantify the joint kinematics of FAI patients compared to healthy control (CTRL) participants.
METHODS: Eleven male patients (7 arthroplasty: 34.6±8.1 years, 25.7±3.2 kg/m2; 4 open: 33.3±7.1 years, 24.9±1.9 kg/m2) and 21 CTRL (2F/19M, 33.4±6.7 years, 25.4±3.3 kg/m2) participants were recruited from the orthopaedic surgeon’s clinical practice. Patients were assigned to either an arthroplasty or open FAI surgery correction. The participants signed prior to their participation a consent form approved by the hospital and university ethics board. Patients agreed to undergo motion analysis prior to and 2 years after the surgery. The CTRL were selected based on similar age and BMI as the FAI group and underwent the same motion analysis protocol.
At the local hospital, CT scan was performed in all participants to confirm an alpha-angle higher than 55º and also establish their pelvic and knee bony landmarks. At the motion laboratory, the participants were outfitted with 45 reflective markers and performed a minimum of five trials of deep squat at a self-selected pace. Three-dimensional joint kinematics (200 Hz) of the lower limbs were captured using a ten-camera motion analysis system (Vicon, UK). Kinematics data were processed in Nexus 1.8.3 (Vicon, UK) using a modified Plug-In-Gait model and exported with a custom MATLAB script (Mathworks, USA) to calculate group averages and extract relevant variables. All trials were time-normalized based on a full squat cycle (descent and ascent phases) and individual averages for each participant were calculated across the trials.
Four kinematic variables were included in the analysis: pelvis, hip, knee, and ankle sagittal angles. The normalized root-mean-square deviation (nRMSD) was calculated between the FAI and the CTRL groups for both pre- and post-surgery conditions, expressed by