Magnitude Of Asymmetry Research Articles

Asymmetry in the Onset of Paraspinal Muscles Activity Differs in Adolescents With Idiopathic Scoliosis Compared With Those With a Symmetrical Spine.

Adolescent idiopathic scoliosis (AIS) is characterized by an asymmetrical formation of the spine and ribcage. Recent work provides evidence of asymmetrical (right versus left side) paraspinal muscle size, composition, and activation amplitude in adolescents with AIS. Each of these factors influences muscle force generation. The timing of paraspinal muscle activation may also contribute to an asymmetry in the timing of forces applied to the spine. The main objectives were to determine (1) whether the timing and asymmetry of erector spinae muscle activation during a rapid bilateral arm raise task differs between adolescents with AIS and those without AIS and (2) whether the magnitude of erector spinae activation asymmetry in AIS is associated with scoliosis curve severity (Cobb angle) or skeletal development level (Risser stage). Finally, (3) we investigated potential kinematic confounders to determine whether symmetry of bilateral rapid arm movements differed between those with and without AIS, and whether any asymmetry in arm movement was associated with erector spinae activation asymmetry. All patients were made aware of the project through flyers at one outpatient spine clinic and a scoliosis rehabilitation clinic in Brisbane, Australia. They were invited between August 2022 and September 2023 to contribute if they met the selection criteria. This cross-sectional study included females with AIS who agreed to participate (n = 24, mean ± SD age of 14 ± 2 years). They all had a primary right-thoracic curve, diagnosed by an orthopaedic specialist. Twenty age- and sex-matched controls (age 13 ± 2 years) who did not have AIS were recruited from the local community. Volunteers (from either group) were excluded if they had any history of spinal surgery, neurological disorders, or musculoskeletal disorders (other than AIS). The experimental task required participants to perform a bilateral rapid arm flexion in response to a visual cue. Muscle activation was recorded using surface electrodes, placed bilaterally on the anterior deltoid and erector spinae adjacent to the C7, T9 (the curve apex for AIS), T12, and L5 vertebrae. Muscle activation onsets were determined from 6 of 10 trials with the quickest deltoid onset for each participant. A linear mixed model (with fixed factors) was used to determine whether activation asymmetry (left-right onset difference) differed between groups (AIS, control) and vertebral level (C7, T9/apex, T12, and L5). Where a group difference in onset asymmetry was identified, the relation of the Cobb angle and Risser stage with the magnitude of asymmetry was evaluated in the AIS cohort using a linear mixed model. Task kinematics, including peak angular arm movement velocity and deltoid onset relative to the light signal, were analyzed using a linear mixed model with group and side as fixed factors. Erector spinae activation timing asymmetry differed between groups at the T9/apex (mean difference 14 ± 23 ms; p < 0.01). In the AIS group, muscle activation was 6 ± 17 ms earlier on the right (convex) relative to the left side of the spine, whereas in controls, activation was 8 ± 19 ms earlier on the left relative to the right side. This difference in activation timing asymmetry between groups was explained by later activation of the T9 level erector spinae muscles on the left (concave) side of the spine in AIS compared with controls (mean group difference of left T9/apex erector spinae onset 13 ± 26 ms; p = 0.01). There were no between-group differences at other vertebral levels. Within the AIS group, no association was observed between the magnitude of the erector spinae activation asymmetry measured at T9/apex and Cobb angle or Risser stage. There were no differences between groups in either the bilateral deltoid onset relative to light or arm peak velocity. Erector spinae muscle activation is asymmetrical at the T9/apex vertebral level during a rapid bilateral arm raise task. This asymmetry was opposite between the AIS and control cohorts, with left-side activation delayed in AIS. It is well established in conditions such as cerebral palsy that muscles forces can influence bone development in children. In children with AIS, there is growing evidence of asymmetrical paraspinal muscle size, composition, and activation amplitude. Each of these factors contribute to paraspinal muscle force generation. Our findings add to what we know by identifying an asymmetry in the timing of erector spinae activation during a well-controlled, bilateral movement task. Combined with previous research, these results support further investigation into whether asymmetrical paraspinal muscle forces might contribute to the curve progression and asymmetrical bony development in AIS. This is important as muscle forces are modifiable through targeted rehabilitation.

Effects of Maturation on the Magnitude and Direction of Asymmetry in Jumping and Change of Direction Speed in Young Elite Football Players.

Gonzalo-Skok, O and Bishop, C. Effects of maturation on the magnitude and direction of asymmetry in jumping and change of direction speed in young elite football players. J Strength Cond Res 39(1): 70-78, 2025-Physical performance is often affected by maturation in young athletes and provides an interesting challenge to optimize performance. The present study analyzed whether maturation affects directional dominance, chronological age, body mass, and biological age predictors and assessed between chronological or biological age-group differences in young footballers. One hundred eight elite male players (U-15 to U-19) were tested on bilateral vertical and unilateral vertical and horizontal jumping, sprinting (40 m), and change of direction (COD) ability over single and multiple CODs (times and the percentage-based COD deficit [%CODD]). Almost half of the players (45%) at post-peak height velocity (PHV) showed consistency in the direction of asymmetry (jumping and COD). Ten-meter sprint time was the main predictor to explain the %CODD. Standing height affects unilateral horizontal jumping, and peak speed and unilateral horizontal jumping were the main predictors for unilateral vertical jumping. Post-PHV reported significantly (p < 0.05, effect size [ES] = 0.76-1.50) greater vertical and horizontal jumping, and linear and COD speed performance than mid-PHV. Significant differences (p < 0.05) in jumping, sprinting, and COD performance were found between U-15 and the rest of groups. Furthermore, the U-16 group showed a significant difference (p < 0.05) to the U-19 (for peak speed) and U-18 groups (for 40-m sprint and peak speed). Significantly (p = 0.04, ES = 0.47) lower %CODD asymmetries were found in mid-PHV compared with post-PHV. The study highlights the impact of maturation on the direction of asymmetry, tending to show the same weak side as maturation increases (i.e., older, and more experienced and mature players). Finally, decreasing between-limbs asymmetry should be considered during maturation, especially as greater football specialization.

Within-session propulsion asymmetry changes have a limited effect on gait asymmetry post-stroke.

Biomechanical gait impairments, such as reduced paretic propulsion, are common post-stroke. Studies have used biofeedback to increase paretic propulsion and reduce propulsion asymmetry, but it is unclear if these changes impact overall gait asymmetry. There is an implicit assumption that reducing propulsion asymmetry will improve overall gait symmetry, as paretic propulsion has been related to numerous biomechanical impairments. However, no work has investigated the impact of reducing propulsion asymmetry on overall gait asymmetry. We aimed to understand how within-session changes in propulsion asymmetry affect overall gait asymmetry, operationalized as the combined gait asymmetry metric (CGAM). We hypothesized that decreasing propulsion asymmetry would reduce CGAM. Methods. Participants completed twenty minutes of biofeedback training designed to increase paretic propulsion. We calculated the change in propulsion asymmetry magnitude (Δ|PA|) and the change in CGAM (ΔCGAM) during biofeedback relative to baseline. Then, we fit a robust linear mixed-effects model with ΔCGAM as the outcome and a fixed effect for Δ|PA|. Results. We found a positive association between Δ|PA| and ΔCGAM (β = 2.6, p = 0.002). The average Δ|PA| was - 0.09, suggesting that, on average, we would expect a CGAM change of 0.2, which is 0.5% of the average baseline CGAM value. Conclusions. Reducing propulsive asymmetry using biofeedback is unlikely to produce substantial reductions in overall gait asymmetry, suggesting that biofeedback-based approaches to reduce propulsion asymmetry may need to be combined with other interventions to improve overall gait asymmetry. Clinical Trial Registration . NCT04411303.

Asymmetries in foveal vision.

Visual perception is characterized by known asymmetries in the visual field; human's visual sensitivity is higher along the horizontal than the vertical meridian, and along the lower than the upper vertical meridian. These asymmetries decrease with decreasing eccentricity from the periphery to the center of gaze, suggesting that they may be absent in the 1-deg foveola, the retinal region used to explore scenes at high-resolution. Using high-precision eyetracking and gaze-contingent display, allowing for accurate control over the stimulated foveolar location despite the continuous eye motion at fixation, we investigated fine visual discrimination at different isoeccentric locations across the foveola and parafovea. Although the tested foveolar locations were only 0.3 deg away from the center of gaze, we show that, similar to more eccentric locations, humans are more sensitive to stimuli presented along the horizontal than the vertical meridian. Whereas the magnitude of this asymmetry is reduced in the foveola, the magnitude of the vertical meridian asymmetry is comparable but, interestingly, reversed: objects presented slightly above the center of gaze are more easily discerned than when presented at the same eccentricity below the center of gaze. Therefore, far from being uniform, as often assumed, foveolar vision is characterized by perceptual asymmetries. Further, these asymmetries differ not only in magnitude but also in direction compared to those present just ~4deg away from the center of gaze, resulting in overall different foveal and extrafoveal perceptual fields.

Assessing the magnitude and direction of asymmetry in physical tests and morphological measurements in professional female soccer athletes

ObjectivesTo analyze the magnitude and direction of inter-limb asymmetries in vertical jump, T-test, isokinetic peak torque, and muscle volume in professional female soccer players. MethodsSixteen female soccer players participated in the study (22.7 ± 3.5 years, 60.4 ± 12.7 kg, 164.2 ± 8.7 cm). The following tests were applied; the unilateral countermovement jump (CMJ), T-test (agility), peak torque of concentric knee extensor (PT_Con_Q), concentric and eccentric knee flexor (PT_Con_H; PT_Ecc_H), and muscle volume of quadriceps (MV_Q) and gastrocnemius (MV_G). The interlimb asymmetry magnitude was calculated as the percentage difference between the stronger and weaker limbs. For the direction of asymmetry, a negative sign (−) was assigned when the non-dominant lower limb was the stronger one, and a positive sign (+) when the dominant lower limb was the stronger one. ResultsThe asymmetry (%) values varied from 0.7 to 11.9%, with the highest values of asymmetry found in the CMJ, PT_Con_Q, PT_Con_H, and PT_Ecc_H tests. Moderate levels of agreement were observed for CMJ - Vol_G (K = 0.53; 75% agreement); PT_Con_Q - PT_Con_H (K = 0.48; 75% agreement); T-test - PT_Ecc_H (K = 0.43; 68.7% agreement). Fair levels of agreement were found between the T-test - Vol_Q (K = 0.21; 62.1% agreement); PT_Con_Q - PT_Ecc_H (K = 0.36; 68.8% agreement); and PT_Con_H - PT_Ecc_H (K = 0.31; 68.8% agreement). ConclusionsWe concluded that of greater asymmetries in the vertical jump and isokinetic torque tests. The direction of the asymmetry seems highly variable, however, the isokinetic tests showed greater agreements with the other tests.

Association of Seizure Foci and Location of Tau and Amyloid Deposition and Brain Atrophy in Patients With Alzheimer Disease and Seizures.

Alzheimer disease (AD) is associated with a 2 to 3-fold increased risk of developing late-onset focal epilepsy, yet it remains unclear how development of focal epilepsy in AD is related to AD pathology. The objective of this study was to examine spatial relationships between the epileptogenic zone and tau deposition, amyloid deposition, and brain atrophy in individuals with AD who developed late-onset, otherwise unexplained focal epilepsy. We hypothesized that if network hyperexcitability is mechanistically linked to AD pathology, then there would be increased tau and amyloid deposition within the epileptogenic hemisphere. In this cross-sectional study, we performed tau and amyloid PET imaging, brain MRI, and overnight scalp EEG in individuals with early clinical stages of AD who developed late-onset, otherwise unexplained focal epilepsy (AD-Ep). Participants were referred from epilepsy and memory disorders clinics at our institutions. We determined epilepsy localization based on EEG findings and seizure semiology. We quantified tau deposition, amyloid deposition, and atrophy across brain regions and calculated asymmetry indices for these measures. We compared findings in AD-Ep with those in a control AD group without epilepsy (AD-NoEp). The AD-Ep group included 8 individuals with a mean age of 69.5 ± 4.2 years at PET imaging. The AD-NoEp group included 14 individuals with a mean age of 71.7 ± 9.8 years at PET imaging. In AD-Ep, we found a highly asymmetric pattern of tau deposition, with significantly greater tau in the epileptogenic hemisphere. Amyloid deposition and cortical atrophy were also greater in the epileptogenic hemisphere, although the magnitudes of asymmetry were reduced compared with tau. Compared with AD-NoEp, the AD-Ep group had significantly greater tau asymmetry and trends toward greater asymmetry of amyloid and atrophy. AD-Ep also had significantly greater amyloid burden bilaterally and trends toward greater tau burden within the epileptogenic hemisphere, compared with AD-NoEp. Our results reveal a spatial association between the epileptogenic focus and tau deposition, amyloid deposition, and neurodegeneration in early clinical stages of AD. Within the limitations of a cross-sectional study with small sample sizes, these findings contribute to our understanding of the clinicopathologic heterogeneity of AD, demonstrating an association between focal epilepsy and lateralized pathology in AD.

Dynamic three-dimensional facial topography in pediatric facial palsy: Understanding asymmetrical facial contours

BackgroundObjective assessment of facial movements remains pivotal for diagnosis, treatment, and long-term monitoring of patients with facial palsy (FP). This study aims to utilize curvature analysis in pediatric patients with and without FP to define facial contours and to quantify three-dimensional (3D) excursion during smile. MethodsPediatric patients with and without FP had 3D motion capture acquired from rest to maximum smile positions. 3D curvature analysis was performed with a custom MATLAB algorithm. A 40-vertex “smile curve” along the nasolabial fold-cheek-orbit contour was extracted from each patient-specific 3D mesh hemiface. This allowed quantification of excursion and asymmetry for affected vs. unaffected sides in FP patients, and comparison with controls. ResultsTwelve FP (mean 12.5yr., range 5-18) and 12 control (mean 12.1yr., range 5-18) patients were analyzed. Differences in facial contour are intensified during animation, especially in the nasolabial fold, cheek, and periorbital regions of interest and the smile curve which links them. Mean excursion differed significantly between the FP and control groups in all regions of interest (p < 0.0001). ConclusionsCurvature analysis provides insight into the unexplored relationship of the 3D morphological dynamics of the concavity and convexity of the face, to add to the understanding of this complex condition. The magnitude of asymmetry between a FP patient’s affected vs. unaffected smile curve excursion, and comparison to the control group, could allow surgical treatment to be tailored to an individual patient’s dynamic anatomy by identifying and quantifying facial region-specific asymmetry.

The relationship between functional movement patterns, dynamic balance and ice speed and agility in young elite male ice hockey players.

Understanding the relationship between the functional state of the musculoskeletal system and skating performance in ice hockey players is essential, as it can provide valuable insights for the development of training programs tailored to the specific needs of athletes. This study investigated the relationship between functional movement patterns, dynamic balance, and ice speed and agility in young elite male ice hockey players. The study involved sixty elite male ice hockey players aged 14 to 18 years, with an average age of 15.9 ± 0.85 years and training experience ranging from 7 to 9 years. Functional movement patterns were evaluated using the Functional Movement Screen™ (FMSTM). Dynamic balance was assessed using the lower quarter Y-Balance test (YBT-LQ). Fitness tests on ice were conducted using a professional Smart Speed measurement system. Negative correlations were found between the in-line lunge and the results of the 5-m forward (rho = -0.31, p = 0.018) and 5-m backward (rho = -0.27, p = 0.040), as well as between the hurdle step and the 30-m forward skating test result (rho = -0.26, p = 0.043). Positive correlations were observed between shoulder mobility and both forward (5-m: rho = 0.27, p = 0.035) and backward skating results (5-m: rho = 0.35, p = 0.006; 30-m: rho = 0.26, p = 0.047), and between active straight leg rise and both the 5-m forward skating (rho = 0.38, p = 0.002) and agility tests (rho = 0.39, p = 0.002). The study also revealed positive correlations between the magnitude of asymmetries in the anterior reach distance of the right and left legs and the results of 5-m forward (rho = 0.34, p = 0.009) and backward skating (rho = 0.32, p = 0.013). Additionally, a positive correlation was found between the agility test and the magnitude of asymmetries in the posteromedial reach distance (r = 0.32, p = 0.012) as well as the composite YBT score (r = 0.28, p = 0.031). Negative correlations were found between normalized reach distances in the YBT-LQ and performance outcomes in both forward and backward skating, as well as in the agility test, indicating that greater reach distance corresponds to faster skating. These findings suggest the potential impact of balance and hip mobility on skating speed and agility and emphasize the importance of symmetry for optimal performance among ice hockey players.

Triple Jump Performance Parameters and Inter-Limb Asymmetry in the Kinematic Parameters of the Approach Run in International and Paralympic-Level Class T46/T47 Male Athletes

Background/Objectives: The triple jump is included in the Paralympic Athletics competition. The aim of the research was to examine the relationship of the phase ratios and the inter-limb asymmetry in the spatiotemporal parameters of the approach run in Paralympic and international-level Class T46/T47 triple jumpers. Methods: Eleven Class T46/T47 male athletes were recorded during the examined competitions. Step length (SL), frequency (SF), and average velocity (ASV) for the late approach run as well as the length and the percentage distribution of each jumping phase (hop, step, jump) were measured using a panning video analysis method. The inter-limb asymmetry was estimated using the symmetry angle. Results: No significant inter-limb asymmetry was found (p &gt; 0.05). In addition, SL, SF, and ASV were not different (p &gt; 0.05) between the steps initiated from the ipsilateral and the contralateral leg regarding the impaired arm. However, the direction of asymmetry for SF was towards the ipsilateral leg to the impaired arm in the majority of the examined athletes. The maximum speed of the approach was correlated with the triple jump distance and the magnitude of asymmetry for AVS was correlated with the vertical take-off velocity and angle for the step. Conclusions: Since the distance of the triple jump related with the peak approach speed added the negative correlation of peak approach speed with the magnitude of the symmetry angle for SL, it is suggested to minimize the asymmetries in the step characteristics during the approach run to improve triple jump performance in Class T46/T47 jumpers.

An Analytic Characterization of the Limb Asymmetry—Transit Time Degeneracy

Atmospheres are not spatially homogeneous. This is particularly true for hot, tidally locked exoplanets with large day-to-night temperature variations, which can yield significant differences between the morning and evening terminators—known as limb asymmetry. Current transit observations with the James Webb Space Telescope (JWST) are precise enough to disentangle the separate contributions of these morning and evening limbs to the overall transmission spectrum in certain circumstances. However, the signature of limb asymmetry in a transit light curve is highly degenerate with uncertainty in the planet’s time of conjunction. This raises the question of how precisely transit times must be measured to enable accurate studies of limb asymmetry, in particular with JWST. Although this degeneracy has been discussed in the literature, a general description of it has not been presented. In this work, we show how this degeneracy results from apparent changes in the transit contact times when the planetary disk has asymmetric limb sizes. We derive a general formula relating the magnitude of limb asymmetry to the amount by which it would cause the apparent time of conjunction to vary, which can reach tens of seconds. Comparing our formula to simulated observations, we find that numerical fitting techniques add additional bias to the measured time, of generally less than a second, resulting from the occultation geometry. We also derive an analytical formula for this extra numerical bias. These formulae can be applied to planning new observations or interpreting literature measurements, and we show examples for commonly studied exoplanets.

Magnitude and Direction of Interlimb Asymmetry and the Association of Interlimb Asymmetry with Physical Performance in Judo Athletes with Visual Impairment.

For judo athletes with visual impairments and their coaches, understanding possible muscle adaptations can be challenging. As it is commonplace for these adaptations to include interlimb asymmetry, we analyzed the magnitude and direction of interlimb asymmetry in judo athletes with visual impairments and verified the association of this asymmetry with their unilateral physical performances. Participants were 18 elite judo athletes (10 male, 8 female) with visual impairments. These athletes performed three physical tests: countermovement jump (CMJ), medicine ball throw (MBT), and handgrip strength (HGS), while we conducted unilateral right and left side assessments using the interlimb asymmetry equation for each physical test. Our main results showed that the CMJ and MBT tests presented asymmetry values above 10%; with CMJ significantly higher than HGS (p = 0.050), and with inconsistencies across the three tests in the direction of interlimb asymmetry (k = -0.22-0.26). Unilateral CMJ (left limb) was negatively correlated with asymmetry (r = -0.51; p = 0.031), and unilateral MBT (right limb) was positively correlated with asymmetry (r = 0.52; p = 0.024). Based on these results, coaches should prioritize regular assessments of interlimb asymmetry using these specific tests. This data can guide the construction of training programs aimed at minimizing asymmetry and enhancing overall physical performance. Continuous monitoring and adjustment of training strategies based on asymmetry findings are crucial for optimizing muscle balance in judo athletes with visual impairments.

The universe is asymmetric, the mouse brain too.

Hemispheric brain asymmetry is a basic organizational principle of the human brain and has been implicated in various psychiatric conditions, including autism spectrum disorder. Brain asymmetry is not a uniquely human feature and is observed in other species such as the mouse. Yet, asymmetry patterns are generally nuanced, and substantial sample sizes are required to detect these patterns. In this pre-registered study, we use a mouse dataset from the Province of Ontario Neurodevelopmental Network, which comprises structural MRI data from over 2000 mice, including genetic models for autism spectrum disorder, to reveal the scope and magnitude of hemispheric asymmetry in the mouse. Our findings demonstrate the presence of robust hemispheric asymmetry in the mouse brain, such as larger right hemispheric volumes towards the anterior pole and larger left hemispheric volumes toward the posterior pole, opposite to what has been shown in humans. This suggests the existence of species-specific traits. Further clustering analysis identified distinct asymmetry patterns in autism spectrum disorder models, a phenomenon that is also seen in atypically developing participants. Our study shows potential for the use of mouse models to understand the biological bases of typical and atypical brain asymmetry but also warrants caution as asymmetry patterns seem to differ between humans and mice.

Inter-Limb Asymmetry in Female Sepak Takraw Players: An Observational Study

This study investigated the magnitude and direction of inter-limb asymmetry in 21 professional female sepak takraw players across several task-specific tests. Five inter-limb asymmetry assessments were employed: unilateral countermovement jump (Uni-CMJ), bilateral countermovement jump (Bi-CMJ), single-leg hop (SLH), triple hop test (THOP), and isokinetic concentric peak torque of the knee flexors and extensors at 60 deg/s−1, 120 deg/s−1, and 180 deg/s−1 angular velocities. A “true” inter-limb asymmetry was only observed for Uni-CMJ jump height (16.62%) and THOP distance (6.09%). Kappa coefficients demonstrated fair agreement in the direction of asymmetry between the Uni-CMJ and Bi-CMJ tests for jump height (Kappa = 26.67), but only slight agreement for peak force (Kappa = 0.11), propulsive impulse (Kappa = −0.12), and eccentric impulse (Kappa = −0.14). Fair agreement was observed between the SLH and THOP (Kappa = 0.32). Slight to moderate agreement was found for concentric peak torque across angular velocities for the knee extensors (Kappa = 0.08 to 0.48), while fair to nearly perfect agreement was noted for the knee flexors (Kappa = 0.31 to 1). The Uni-CMJ and THOP are most sensitive to detect between-limb asymmetries in female sepak takraw players. Given the inconsistencies in asymmetry direction across tests, monitoring asymmetry direction is important for strength and conditioning.

Seasonal Variations in Performance and Asymmetry Data for Jump and Change of Direction Abilities in Female Soccer Players.

Mainer-Pardos, E, Bishop, C, and Gonzalo-Skok, O. Seasonal variations in performance and asymmetry data for jump and change of direction abilities in female soccer players. J Strength Cond Res XX(X): 000-000, 2024-The study aimed to evaluate the progression of the percentage-based change of direction (COD) deficit (%CODD) over a competitive season, along with its correlation with performance tests and to examine the impact of the magnitude and direction of asymmetry at 4 stages of the season. Forty-seven (U-16, U-18, and U-20), highly trained, female soccer players performed unilateral vertical jumping (countermovement jump [CMJ]) and horizontal jumping (HJ), 10-m sprint, and 180° change of direction (COD180) tests. The %CODD was also calculated. Significant group and time effects (p < 0.05) were observed in CMJ, HJ, 10-m sprint, and COD180 tests, with U-20 players generally outperforming the U-18 and U-16 groups. Nonsignificant differences were reported in the %CODD between any time point or groups throughout the season. Moderate or large significant (r = 0.44-0.64; p < 0.05) relationships were found between %CODD and 10 m. The direction of asymmetry within and between tests at all time points was slight to moderate (k = -0.29 to 0.57). Notwithstanding, 51% of the players showed the best performance in the horizontal jump with the same leg throughout the season, whereas only 36% in %CODD. This study highlights the importance of developing strategies to improve %CODD depending on the player's position demands. Finally, individually monitoring the magnitude and direction of asymmetry can help practitioners monitor the effects of training and competition throughout the season.

Magnitude and direction of shoulder torque asymmetries between different angular velocities in competitive swimmers

ABSTRACT Asymmetries in swimming can be the result of poor technique or coordination between limbs, reducing the ability to produce propulsive force and increasing resistive drag. Therefore, this study aimed to compare the magnitude and determine the consistency of isokinetic peak torque asymmetries between the angular velocities of in the shoulder joint movements of internal and external rotation, flexion, and extension. Twenty-one competitive swimmers performed concentric actions at 60°/s (3 repetitions) and 180°/s (20 repetitions) in the movements of internal and external rotation, flexion, and extension of the shoulders using an isokinetic dynamometer, with the peak torque and asymmetry index being common metrics across the tests. The results showed a greater magnitude of asymmetry in internal rotation (16.86 vs. 9.86; p = 0.007) and flexion (12.06 vs. 7.35; p = 0.008) at 60 vs. 180°/s, respectively. The agreement levels of the direction of asymmetries between angular velocities were fair to substantial (Kappa: 0.40 to 0.69). Evaluating isokinetic torque in different movements and angular velocities resulted in different levels of asymmetry. Muscle force asymmetries can impact propulsion efficiency and movement coordination during swimming. Understanding muscle asymmetries allows the development of targeted and individualised training programmes to correct strength imbalances.

Biomechanics of Insect Flight Stability and Perturbation Response.

Insects must fly in highly variable natural environments filled with gusts, vortices, and other transient aerodynamic phenomena that challenge flight stability. Furthermore, the aerodynamic forces that support insect flight are produced from rapidly oscillating wings of time-varying orientation and configuration. The instantaneous flight forces produced by these wings are large relative to the average forces supporting body weight. The magnitude of these forces and their time-varying direction add another challenge to flight stability, because even proportionally small asymmetries in timing or magnitude between the left and right wings may be sufficient to produce large changes in body orientation. However, these same large-magnitude oscillating forces also offer an opportunity for unexpected flight stability through nonlinear interactions between body orientation, body oscillation in response to time-varying inertial and aerodynamic forces, and the oscillating wings themselves. Understanding the emergent stability properties of flying insects is a crucial step toward understanding the requirements for evolution of flapping flight and decoding the role of sensory feedback in flight control. Here, we provide a brief review of insect flight stability, with some emphasis on stability effects brought about by oscillating wings, and present some preliminary experimental data probing some aspects of flight stability in free-flying insects.

Double Hanle resonance dependence on light polarization angle and transverse magnetic field direction

We present experimental and theoretical investigations of the dependence of double Hanle resonance spectrum on the light polarization angle and the direction of the applied transverse magnetic field (TMF). The experiments are done for Fg=2→Fe=1 transition of 87Rb D1 line using a rubidium vapor cell containing buffer gas. We show that a small light polarization component along the direction of TMF introduces asymmetry in the double Hanle resonance signal. Both the magnitude and sign of asymmetry in the signal are sensitive to the TMF orientation, suggesting a possible method for in-situ measurement of the direction of the magnetic fields generated by the coils. The physical origin of this asymmetry is explained by considering the redistribution of population among the ground-state Zeeman sublevels in the presence of TMF. In addition, we systematically vary both the polarization angle and TMF direction to study their effect on the line profile of Hanle resonances. We demonstrate that a double Hanle resonance changes to a dark Hanle resonance by rotating the light polarization vector irrespective of the TMF direction. We have developed a simple theoretical model based on a degenerate two-level system to explain our experimental observations.

Electrocortical theta activity may reflect sensory prediction errors during adaptation to a gradual gait perturbation

Locomotor adaptation to abrupt and gradual perturbations are likely driven by fundamentally different neural processes. The aim of this study was to quantify brain dynamics associated with gait adaptation to a gradually introduced gait perturbation, which typically results in smaller behavioral errors relative to an abrupt perturbation. Loss of balance during standing and walking elicits transient increases in midfrontal theta oscillations that have been shown to scale with perturbation intensity. We hypothesized there would be no significant change in anterior cingulate theta power (4–7 Hz) with respect to pre-adaptation when a gait perturbation is introduced gradually because the gradual perturbation acceleration and stepping kinematic errors are small relative to an abrupt perturbation. Using mobile electroencephalography (EEG), we measured gait-related spectral changes near the anterior cingulate, posterior cingulate, sensorimotor, and posterior parietal cortices as young, neurotypical adults (n = 30) adapted their gait to an incremental split-belt treadmill perturbation. Most cortical clusters we examined (&gt;70%) did not exhibit changes in electrocortical activity between 2–50 Hz. However, we did observe gait-related theta synchronization near the left anterior cingulate cortex during strides with the largest errors, as measured by step length asymmetry. These results suggest gradual adaptation with small gait asymmetry and perturbation magnitude may not require significant cortical resources beyond normal treadmill walking. Nevertheless, the anterior cingulate may remain actively engaged in error monitoring, transmitting sensory prediction error information via theta oscillations.

Effect of Sex and Lateral Ankle Sprain History on Dorsiflexion Range Of Motion Asymmetry During the Weight Bearing Lunge Test.

Reduced dorsiflexion range of motion (DFROM) which is commonly seen following lateral ankle sprain (LAS) has the potential to influence lower extremity biomechanics which have been linked to increased injury risk in the female athlete. Current research on the effect of sex and LAS history on DFROM is limited. This study had three aims 1) to determine the effect of sex, leg dominance and LAS history on DFROM, 2) to determine the effect of sex and LAS history on magnitude of DFROM symmetry and 3) to examine the association of sex on direction (whether dominant or non-dominant limb had the higher DFROM) of symmetry. Cross-Sectional Study. DFROM was measured bilaterally in 105 recreational athletes all participating in multidirectional sports using the tape measurement method during the weight bearing lunge test (WBLT). A mean of three measurements was used for analysis. A 3-way mixed ANOVA was carried out to determine the interaction between sex, LAS history and leg dominance on DFROM and a 2-way ANOVA for the effect of sex and LAS history on asymmetry. A chi-square test was used to determine the association of sex and direction of asymmetry. The results indicate no significant effect of sex, LAS history, and leg dominance on DFROM (p=0.65). Main effects were significant for sex and LAS on DFROM. The mean asymmetry for all participants was reported as 12.25±14.76cm. No significant effect of sex and LAS history on magnitude of asymmetry was reported. There was a significant association of sex and direction of asymmetry (χ2(1) = 11.26, p = 0.00). Sixty-five-point two percent of males were shown to have higher DFROM of their non-dominant limb compared to 75% of females who were higher in their dominant limb. Findings from this study suggest that DFROM is affected by sex and LAS history. While females have increased DFROM compared to males, those with LAS history are more likely to have a decreased DFROM on the involved side. The results also indicate that interlimb asymmetries in DFROM are present in athletes, therefore practitioners should exercise caution when using bilateral comparisons in injury and return to play assessments. 2b.

Graph‐theoretical chirality measure and chirality–property relations for chemical structures with multiscale mirror asymmetries

AbstractChirality is an essential geometric property unifying small molecules, biological macromolecules, inorganic nanomaterials, biological microparticles, and many other chemical structures. Numerous chirality measures have attempted to quantify this geometric property of mirror asymmetry and to correlate these measures with physical and chemical properties. However, their utility has been widely limited because these correlations have been largely notional. Furthermore, chirality measures also require prohibitively demanding computations, especially for chiral structures comprised of thousands of atoms. Acknowledging the fundamental problems with quantification of mirror asymmetry, including the ambiguity of sign‐variable pseudoscalar chirality measures, we revisit this subject because of the significance of quantifying chirality for quantitative biomimetics and describing the chirality of nanoscale materials that display chirality continuum and scale‐dependent mirror asymmetry. We apply the concept of torsion within the framework of differential geometry to the graph theoretical representation of chiral molecules and nanostructures to address some of the fundamental problems and practical limitations of other chirality measures. Chiral gold clusters and other chiral structures are used as models to elaborate a graph‐theoretical chirality (GTC) measure, demonstrating its applicability to chiral materials with different degrees of chirality at different scales. For specific cases, we show that GTC provides an adequate description of both the sign and magnitude of mirror asymmetry. The direct correlations with macroscopic properties, such as chiroptical spectra, are enhanced by using the hybrid chirality measures combining parameters from discrete mathematics and physics. Taking molecular helices as an example, we established a direct relation between GTC and optical activity, indicating that this chirality measure can be applied to chiral metamaterials and complex chiral constructs.