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: Amir

Eccentric training may affect the longitudinal adaptation of the muscle. Usually the muscle fiber lengthening during eccentric training is measured by the joint kinematics. Due to tendon compliance, this method offers insufficient information about the muscle fiber behavior. The present study investigated the muscle fiber behavior of the Vastus Lateralis muscle (VL) during eccentric knee contractions in humans by measuring the changes of fascicle length in vivo with ultrasonography, at force levels of 65% and 95% of the maximum voluntary isometric contraction force (MVC). Seven young adults were tested by a Biodex. They performed eccentric knee contractions with one leg at 65% and 95% of their MVC (knee angle 25°-100°, angular velocity 90°/s). Potential joint axis deviations were recorded using a Vicon camera system. Exerted knee moments were captured synchronously with the Vicon system at 1000Hz. Fascicle length of the VL muscle visualized by a 10cm Ultrasound prob. The means and standard deviations of fascicle elongation at 65% and 95% of the MVC were 42.71±8.54mm and 39.11±10.64mm respectively, with no statistically significant difference between both conditions. All subjects showed a plateau or slide decrease in fascicle length at the beginning of the movement. This slight decrease in fascicle length, which occurs despite a lengthening of the VL muscle-tendon unite, can be explained by the tendon compliance. The similar fascicle elongation between the two conditions (65% vs. 95% MVC) reveals that the amplitude of the force level during eccentric knee extension contractions does not affect the lengthening of the fascicle.


Listed In: Biomechanics, Other
Name: Valentina

In the past we have shown that exposure to increasing amplitudes of Galvanic vestibular stimulation (GVS) induces a corresponding increasing deficit in postural control, cognition and autonomic function. Previous studies have suggested that suprathreshold GVS induces a similar pattern of postural instability as the one observed on bilateral vestibular loss. The aim of the present study was to determine whether different current intensities would affect somatosensory, visual, and vestibular sensory system similarly to patient affected by vestibular deficits. We assessed postural control in unilateral (right and left) and bilateral vestibular loss patients, an aged matched healthy control group, and during pseudorandom binaural bipolar GVS in healthy subjects at one of three current amplitudes (1 mA, 3.5 mA, 5 mA). Balance was assessed with sensory organization test (SOT) that quantifies the effectiveness of vestibular, visual and somatosensory input to postural control. Results showed that GVS significantly affects vestibular control of posture compared to baseline at all current amplitudes, whereas somatosensory and visual performance was unaffected. Vestibular patients showed a significant decrease in vestibular and visual response compared to control. Suprathreshold GVS 5 mA showed a similar large effect size to unilateral and bilateral vestibular loss patients relative to their aged matched control. NASA NCC 9-58 and NNX09AL14G


Name: Matthias-K

In the current study, we aimed to determine if differences in drop jump height or motor task execution strategy between young and middle-aged adults exist, when triceps surae MTU capacities (muscle strength and tendon stiffness) were matched.
The triceps surae MTU biomechanical properties of 29 middle-aged and 26 younger adults were assessed during isometric voluntary ankle plantarflexion contractions of the dominant leg using a custom-made dynamometer and ultrasonography simultaneously. The 12 young adults with the lowest triceps surae muscle strength and the 12 middle-aged adults with the greatest muscle strength then completed a series of drop jumps from different heights. Ground contact time, average vertical ground reaction force, average mechanical power and jumping height were recorded.
Younger and middle-aged adults attained comparable jumping heights independent of the drop jump height. There were significant age effects on ground contact time and average vertical ground reaction force during ground contact phase, with the middle-aged adults showing higher ground contact times but lower forces, leading to a significant age effect on mechanical power. Significant correlations were found between triceps surae MTU capacities and drop jump height.
The results of the current study demonstrate that when triceps surae MTU capacities are matched, young and middle-aged adults show comparable performance of a jumping task, despite having different motor strategies. Finally, the results suggest that neuromuscular factors other than maximum isometric strength and tendon stiffness may influence motor task execution strategy during jumping.


Name: nathalie

For lower limb amputees graded walking imposes a high level of motor ability, due to the missing proprioceptive feedback of the limb, and the necessary compensation mechanisms. In order to facilitate gait a focus in prosthesis research is the development of the prostheses ankle joints from rigid to moveable. Therefore, the aim of this case study was to analyse the effects of three different prostheses with a rigid and a moveable ankle joint during graded walking of a unilateral amputee.
One male unilateral transfemoral amputee was recruited for this study and a comparison of following three prostheses (endolite, Germany) was performed: Elan (movable ankle joint with flexible resistance), Echelon (movable ankle joint with steady resistance) and Esprit (rigid ankle joint). Kinematic (12 cameras, Vicon, UK, 250 Hz) and kinetic (2 force plates, AMTI, MA, 1000 Hz) data were recorded during self-paced walking on a 6 m ramp, which was set to the inclinations of -12°, -4°, 0°, 4° and 12°. Following gait parameters, ground reaction forces, joint angles and joint moments were calculated.
Gait parameters, ground reaction forces and joint angles were marginally influenced by the different prosthetic designs, but major changes occurred on the joint moment level. The use of the rigid ankle prosthesis Esprit induced up to 10 times higher joint moments compared to the moveable ankle joint prostheses. This case study showed that a moveable ankle joint can reduce the joint moments during graded walking, which might be advantageous to use for transfemoral amputees in graded walking.


Listed In: Biomechanics, Gait
Name: afalaki

Over the past years, we have developed a test for postural stability based on the theory of synergies stabilizing salient performance variables. In this study, effects of Parkinson's disease (PD) and dopamine-replacement therapy on multi-muscle synergies stabilizing the center of pressure (COP) coordinate were explored between: (1) a cohort of 11 patients without clinically identifiable postural problems (Hoehn-Yahr stage II) and 11 age-matched controls, and (2) a cohort of 10 patients tested off- and on-medication, with and without postural problems (stage II and III, n = 5 per stage). Participants stood on a force platform and performed cyclical body sway at 0.5 Hz along the anterior-posterior direction. Electromyographic signals from 13 leg and trunk muscles were used to compute: (1) the amount of inter-cycle variance that did not affect (VUCM) and affected (VORT) COP coordinate, and (2) the magnitude of the cycle-to-cycle motion that did not change (motor equivalent: ME) and changed (non-motor equivalent: nME) the COP coordinate. We hypothesized that both methods would produce indices sensitive to PD and dopaminergic medications. Compared to controls, patients showed significantly smaller inter-cycle VUCM and ME components suggesting a less flexible, and hence less stable, behavior. Moreover, inter-cycle variance within/orthogonal to the UCM correlated with ME/nME displacements. Results suggest clinical utility of variance and motor equivalence analyses of postural instability in early stages of PD and quantifying the effects of dopamine-replacement drugs. The analysis of motor equivalence is particularly attractive because it requires only a handful of trials (observations).


Listed In: Neuroscience
Name: bwannipa

Objective: To evaluate the effect of auditory cues toward postural control in patients with Parkinson's disease (PD).
Background: Auditory cues have been proved to be one of rehabilitation strategies for PD [1]. Most of Parkinson's Disease patients present postural instabilities regarding the severity of the disease [2, 3]. Rhythmic Auditory Stimulation (RAS) has been justified to be a standardized neurological motor therapy (NMTs) in PD, which cue-ing benefits may be associated with the activation of cerebellum-thalamic-cortical circuitry [4]. A potential method to stimulate the putamen that might help regulate PD brain's circuits could be providing music as a rhythmical cue [4]. A distinct manifestation in PD is also the arm swing reduction [5] which limits the capability of maintaining balance. It is rare to explore the static standing balance in Parkinson's Disease.
Methods: 5 idiopathic PD patients (5 female) aged 72.6 ± 2.51 years, duration of the disease 15 ± 1.22 years (mean ± SD), H&Y 2.5-3 participated in this study. They were recruited from Yawata Medical Center, Ishikawa, Japan in June and November, 2014. The subjects were instructed to stand on the balance platform (Nintendo Wii Fit) and swing arm; Alternation (Alt) and Synchronization (Syn) in 3 scenarios; with no auditory cues (AC), with AC 5% increased and with AC 5 % decreased. The data were analyzed by Wilcoxon Signed Ranks Test and the dimensional clustering method [6] on MATLAB.
Results: Tempo at 95% improved area, RMS and Min ML in Alternation, and decreased the path length in rest 2. Tempo at 105% decreased area and RMS in rest 2 statistically significant. A case with H&Y stage 3 showed poorer postural control in both Antero-Posterior (AP) and Medio-Lateral (ML) directions. Most cases presented the higher Center of Pressure (CoP) displacement in ML direction. AC with arm swing regulated the pattern of CoP trajectories.
Conclusions: Auditory cues with arm swing - Alternation improved postural control in the PD patients. This concept might be considered clinically to be a rehabilitation program for Parkinson's disease (PD) to improve standing balance. It is a need to enlarge the sample size and develop more rehabilitation programs for improving balance in PD.


Name: tiffytiru

Background: Patellofemoral pain (PFP) is a common condition seen in orthopedic practice. A commonly cited hypothesis as to the cause of PFP is increased patellofemoral joint (PFJ) stress secondary to abnormal lower extremity kinematics (ie. excessive hip internal rotation and knee valgus). However, the influence of these motions on PFJ contact mechanics is unknown.

Purpose: To assess the influence of hip rotation and knee valgus on PFJ stress using finite element (FE) analysis.

Methods: Patella cartilage stress profiles for a healthy participant were quantified utilizing a subject-specific FE model. Input parameters included: joint geometry, quadriceps muscle forces, and weight-bearing PFJ kinematics. Using a nonlinear FE solver, quasi-static loading simulations were performed to quantify patella cartilage stress during a static squatting maneuver (45° knee flexion). To simulate hip rotation (0-8°) and knee valgus (0-12°), the femur and tibia were rotated in the transverse and frontal plane respectively in 2° increments.

Results: Increasing hip rotation resulted in a linear increase in patella cartilage stress. In contrast, increasing knee valgus resulted in a decrease in patella cartilage stress. The combination of hip rotation and knee valgus did not result in higher PFJ cartilage stress compared to isolated hip rotation.

Conclusions: Patella cartilage stress appears to be influenced to a greater degree by hip internal rotation as opposed to knee valgus. Surprisingly, higher degrees of knee valgus resulted in decreased cartilage stress (in the absence of hip rotation). Our finding supports the premise that persons exhibiting excessive hip internal rotation may be pre-disposed to elevated patella cartilage stress.


Name: pranav-parikh@u...

Transcranial anodal stimulation (tDCS) improves manual dexterity in healthy old adults. The underlying changes in finger force behavior for this improved dexterity have not been reported. Here, we investigated the effects of tDCS (20-min) over primary motor cortex (M1) combined with repeated practice on the Grooved pegboard test (tDCS+MP) on the fingertip forces applied to an object during grasp and manipulation. Eight right-handed able-bodied individuals (60-85 years) participated in a sham-controlled, single-blinded study. Each participant received anodal and sham intervention in two sessions at least 5-day apart. Before and after intervention, they performed a ‘key-slot’ task that required inserting a slot on an object onto a stationary bar, an isometric force production task using a pinch grip, and the Grooved pegboard test. Anodal relative to sham tDCS+MP allowed participants to better retain the improved performance on the pegboard test. For the isometric task, anodal tDCS+MP significantly increased the variability of force compared to sham tDCS+MP. More importantly, the improved retention of performance post-anodal tDCS correlated with the reduction in force angle variability on the key-slot task, but not with the change in force variability on the isometric task. Our findings suggest that anodal tDCS+MP facilitated retention of learning on a skillful manual task in healthy old adults, consistent with the role of M1 in retention of learning versus skill acquisition. Furthermore, improved force steadiness is one of the potential mechanisms through which short-term anodal tDCS during motor training yields improved performance on a functional task.


Name: Florian Paternoster

When an active muscle is stretched, the resulting post-eccentric steady-state force is known to be greater than the isometric force at the corresponding muscle length. The aim of our research was to clarify if residual force enhancement (RFE) is relevant for voluntary human muscle action in everyday like scenarios. Therefore 13 healthy subjects participated in our study and had to perform bilateral leg extensions using a motor-driven leg press dynamometer, measuring external reaction forces (Fext) as well as activity of 9 lower extremity muscles. In addition, ankle (Ma) and knee (Mk) joint torque were calculated using inverse dynamics. Subjects performed isometric and isometric-eccentric-isometric contractions (20° stretch, ω=60°/s) at 30% of maximum voluntary activation. Visual feedback of VL muscle activation was given to control submaximal muscle action. We did not find differences in VL activation level between contraction conditions and time points. Mean VL activity ranged between 29.1 ± 2.2% and 29.8±2.5% MVA. We found significantly enhanced Fext (p < 0.002) as well as joint torques in knee (p < 0.002) and ankle joint (p < 0.033) for all instances in time. In summary RFE seems to be relevant in everyday like human motion.


Name: rakshatha

Multisensory integration is driven by a process of sensory reweighting during which each input is assigned a weight depending on the current functional state of a particular sensory system, the task itself and the context in which it is being performed. The primary aim of this study was to determine which of the two inputs between ankle proprioception and vision is upweighed during a postural control task when the two inputs provide conflicting information pertaining to direction of body sway. Achilles tendon vibration and visual flow were used to create sensory conflict, which produced center of pressure (COP) sway in opposite directions when applied independently. The baseline conditions (1) consisted of eyes open quiet stance condition, eyes closed with vibration applied on the Achilles tendons (2) and eyes open with visual flow (3). The experimental condition simultaneously combined vibration and visual flow. COP excursions were recorded in 10 healthy young adults to evaluate the magnitude and direction of sway produced by vibration and/or visual flow. Additionally, lower body joint kinematics were evaluated to understand the multi-segmental strategies and their adaptation to the various sensory manipulations. The results showed that visual flow moderated the extent of backward COP and ankle angular displacement produced when vibration was applied independently. Additionally, visual flow was also found to reduce the extent of predominant hip strategy generated by ankle vibration. The findings show that visual input plays a significant role in maintaining stability and that ankle proprioception is downweighed during conflicts between vision and proprioception. This has important implication for balance training using controlled visual flow in patients with balance disorders and elderly.