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: chigh

Previous research has shown the utility of vibrotactile feedback to improve postural sway characteristics in persons with vestibular deficits. Tactile feedback given through vibration has been used more as a modality of training but immediate effects on postural control among older adults have not been investigated.
PURPOSE: To compare the immediate effects of tactile vibration on postural sway in healthy older adults in challenging stance and sensory conditions. METHODS: 10 healthy older adults (76.4 ± 6.8years), performed five standing balance conditions on a AMTI forceplate for 30s each: feet together on firm surface eyes open (C1), eyes closed (C2); feet together on foam surface eyes open (C3), eyes closed (C4), and tandem stance on firm surface eyes open (C5). Participants did 2 trials of each condition both with and without vibrotactile feedback. The feedback was given using a waist belt with sensors that were activated when participants swayed in a particular direction as detected by an Xbox Kinect camera (Sensory Kinetics system; Engineering Acoustics, Casselberry, FL). Center of pressure sway area was compared within each condition using a paired samples t-test to estimate the effect of vibration. RESULTS: See Table 1. Since only 5 subjects could complete C4 data was not included in statistical analysis. CONCLUSION: Tactile vibration did not acutely effect postural sway in challenging stance conditions in healthy older adults. Long term effects of tactile vibration on postural sway in challenging stance conditions need to be investigated.

Listed In: Physical Therapy
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.

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: bryappie

Footwear plays a significant role in, and can influence children’s gait. Footwear type is especially important as a child grows and develops from a novice to an expert walker. Compared to barefoot walking, children generally have increased spatiotemporal (ST) gait parameters while walking with footwear. Gait variability has also shown to be affected by footwear. The degree of stiffness in footwear could have a large influence on children’s gait and variability. This study investigated effects of footwear stiffness on ST gait parameters and gait variability in novice walkers. Children with an average age of 33.3 ( 7.0) months participated in a single data collection. Heel and toe marker positions were acquired for one minute of walking per condition. Participants walked on the treadmill in three levels of footwear stiffness (rigid: hard-soled stiff shoe, semi-rigid: EVA sole athletic shoe, compliant: moccasin soft-sole shoe) and barefoot. ST gait parameters and gait variability were calculated for each condition using marker. and treadmill forces. ST parameters all increased in the rigid and semi-rigid footwear conditions compared to soft-sole and barefoot. Interestingly, there were no differences between barefoot and wearing a moccasin for any of the ST variables. There were no differences in SD and COV between any of the footwear conditions. The moccasin shoe promotes walking most similar to normal barefoot walking. Standard measures of variability failed to detect differences between footwear conditions. Further investigation into different measurements is necessary to parse out what effect footwear has on children’s gait variability.

Listed In: Biomechanics, Gait
Name: stahl22

Purpose: To validate an instrumented figure skating blade that is designed to measure impact forces while skating. Methods: Seven subjects (Age: 21.3±2.8 yrs, Ht: 166.9±2.5 cm, Mass: 64.7±7.9 kg) performed 20 landings each onto artificial ice while landing on the instrumented blade from heights of 17.5cm, 25cm, and 33cm. A custom instrumented blade calibrated to measure in forces in Newtons (N) was used to measure impact forces (1000Hz) during landings. These forces were compared to forces obtained while subjects landed on AMTI force plates located underneath the artificial ice surface. Boot angle (250Hz) and force plate data (1000Hz) were collected using Vicon Nexus. Custom LabVIEW programs were used to determine peak force, loading rate, impulse, and the correlation between the blade force data and the force plate data. Paired T-tests were used to compare peak force, loading rate, and impulse between the blade and force plate data. Alpha = 0.05. Results: Correlations between the blade force data and force plate data were good to excellent: mean r (±SD) = .86 ± 0.08. No significant differences were found for peak force and impulse between the blade and force plate data. Peak force means (±SD) were 1353.7 ± 352.2 N for the blade and 1361.2 ± 309.7 N for the force plate (p=.86). Conclusion: The custom instrumented blade is a valid tool for measuring peak forces and impulse during landings. Current research is focused on increasing the gain of the instrumented blade to improve loading rate accuracy.

Listed In: Biomechanics
Name: sunkukwon

Chronic ankle instability (CAI) patients often exhibit altered walking mechanics, due to strength and proprioceptive deficits associated with CAI. Reduced strength and proprioception function may alter walking energetic patterns, by reducing energy absorption and generation capability. It is unclear whether strength and proprioceptive training can affect walking energetics for CAI patients. PURPOSE: To examine the effect of a 6-week ankle and hip rehab program on ankle, knee, and hip joint energetic patterns during walking in CAI patients. METHODS: 15 CAI patients (23 ± 2 yrs, 178 ± 8 cm, 76 ± 9 kg, 83 ± 7% FAAM ADL, 56 ± 10% FAAM Sports, 3.6 ± 1.1 MAII, 4.7 ± 2.0 ankle sprains) performed ankle and hip strength and proprioceptive exercises (i.e., theraband, wobble board, etc.) 3 times per week, for 6 weeks (rehab group). 14 CAI patients (22 ± 2 yrs, 177 ± 9 cm, 75 ± 12 kg, 81 ± 9% FAAM ADL, 56 ± 12% FAAM Sports, 3.4 ± 1.2 MAII, 5.9 ± 3.3 sprains) performed no rehab exercises (control group). We measured ankle, knee, and hip joint power during walking for all patients before and after 6 week duration. Functional statistics (α = 0.05) were used to evaluate the influence of the rehab exercises on joint power for both groups across the entire stance phase of walking. RESULTS: The rehab intervention resulted in up to 0.07 W/kg more positive ankle power (concentric) between 19 and 26% of stance and up to 0.06 W/kg more positive knee power (concentric) between 40 and 48% of stance. No changes were detected in hip joint power during the stance phase of walking. CONCLUSION: Strength and proprioceptive training resulted in an improved gait energetic efficiency via increased ankle and knee power generation during mid-stance. As greater muscular strength can lead to an increase in power absorption and generation, the intervention focusing on strength could be beneficial in improving walking energetics in a CAI population.

Listed In: Biomechanics, Gait
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: jastein

Mechanography during the vertical jump test allows for evaluation of force-time variables reflecting jump execution, which may enhance screening for functional deficits that reduce physical performance and determining mechanistic causes underlying performance changes. However, utility of jump mechanography for evaluation is limited by scant test-retest reliability data of force-time variables. Purpose: To examine test-retest reliability of jump execution variables assessed from mechanography using two different protocols. Methods: 32 women (mean ± SD: age = 20.8 ± 1.3 yr, height = 167.6 ± 6.3 cm, mass = 68.2 ± 12.7 kg) and 16 men (age = 22.1 ± 1.9 yr, height = 181.5 ± 5.0 cm, mass = 94.1 ± 24.6 kg) attended a familiarization session followed by two testing sessions, all one week apart, during which they performed the vertical jump test and had mechanography data recorded. Participants performed six squat jumps (SJ) per session, with squat depth self-selected for the first three jumps and controlled using a goniometer to 110º knee flexion for the remaining three jumps. Raw data were sampled at 1,000 Hz and filtered with a cutoff frequency of 90.9 Hz using Bertec Digital AcquireTM. Jump execution variables were calculated using a macro program in Microsoft Visual Basic. Eight force-time variables were assessed. Test-retest reliability was quantified as the systematic error (using %difference between jumps), random error (using coefficients of variation), and test-retest correlations (using intraclass correlation coefficients).Results: Jump execution variables demonstrated good reliability, evidenced by very small systematic errors (mean ±95%CI: –1.2 ±2.3%), small random errors (mean ±95%CI: 17.8 ±3.7%), and very strong test-retest correlations (range: 0.73-0.97). Differences in random errors between controlled and self-selected protocols were negligible (mean ±95%CI: 1.3 ±2.3%). Conclusion: Jump execution variables demonstrated good reliability, with no meaningful differences between the controlled and self-selected SJ depth protocols. To simplify testing, a self-selected SJ depth protocol can be used to assess force-time variables with negligible impact on measurement error

Listed In: Biomechanics
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: lschroe1

Collegiate softball has become increasingly popular since the passage of Title IX. As with any sport, injuries are a common occurrence. Interestingly, the base runner is at the highest risk of injury, and rounding the base, specifically, has resulted in approximately 187 game-day injuries. Rounding the base involves planting the right foot on a raised surface and cutting to the left, a dynamic movement often associated with noncontact ACL injuries. Frontal plane loading and unbalanced quadriceps-to-hamstring co-contraction indices (Q:H CCI) have been associated with increasing the likelihood of noncontact ACL injuries occurring. Neuromuscular abnormalities pre- and post-contact have also been suggested to increase the risk of injury. To date, no study has analyzed the effect of rounding a base on noncontact ACL injury risk factors in softball players. Nine recreationally active females completed two base conditions. The first simulated rounding a base with no base on the force platform (NB), and the second simulated rounding a base with a base on the force platform (WB). Three-dimensional motion capture, one force platform, and electromyography were utilized. Results indicated the WB condition reduced the risk of noncontact ACL injury by decreasing frontal plane loading. Movement patterns at the ankle and abnormal foot strikes may provide a better explanation for why noncontact ACL injuries occur while rounding first base. Post-contact Q:H CCI was significantly greater than pre-contact, indicating significantly greater quadriceps activity post-contact. Neuromuscular training could potentially reduce the load applied to the ACL and decrease the risk of injury.