Mediolateral Research Articles

Postural Control, Dual Task Performance and Executive Function Following an Ultramarathon.

As research into the postural and cognitive effects of ultramarathon running is sparse and still needed, we investigated the effect of ultramarathon running on runners' postural control, dual task postural control and a measure of executive function-the flanker test, expecting fatigue-related deterioration on each measure. We used a pre- and post-test research design with 14 runners who completed (a) postural assessment with eyes open and closed, on a flat surface and on foam during (b) a two-choice reaction time dual task postural assessment, and (c) an executive function modified flanker task. With regard to postural stability, we observed, after running, increased anterior-posterior (AP) path length and AP root mean square (RMS) and reductions in both mediolateral (ML) RMS and ML median frequency. Dual task analysis showed reduced ML RMS prior to the race, whereas the effect was absent afterwards. Reaction times were not significantly altered between pre-post or surface conditions assessments. There were no statistically significant differences in mean modified flanker scores before and after the race. These data demonstrated that, following an endurance run, there were plane specific movement adaptations in postural sway that may have resulted from neuroprotective changes under extreme fatigue.

On the impact of the erroneous identification of inertial sensors' locations on segments and whole-body centers of mass accelerations: a sensitivity study in one transfemoral amputee.

The kinematics of the body center of mass (bCoM) may provide crucial information supporting the rehabilitation process of people with transfemoral amputation. The use of magneto-inertial measurement units (MIMUs) is promising as it may allow in-the-field bCoM motion monitoring. Indeed, bCoM acceleration might be obtained by fusing the estimated accelerations of body segments' centers of mass (sCoM), the formers being computed from the measured accelerations by segment-mounted MIMUs and the known relative position between each pair of MIMU and underlying sCoM. This paper investigates how erroneous identifications of MIMUs positions impact the accuracy of estimated 3D sCoM and bCoM accelerations in transfemoral amputee gait. Using an experimental design approach, 215 simulations of erroneous identifications of MIMUs positions (up to 0.02 m in each direction) were simulated over seven recorded gait cycles of one participant. MIMUs located on the trunk and sound lower limbs were shown to explain up to 77% of the variance in the accuracy of the estimated bCoM acceleration, presumably due to the higher mass and/or angular velocity of these segments during gait of lower-limb amputees. Therefore, a special attention should be paid when identifying the positions of MIMUs located on segments contributing the most to the investigated motion. Sensitivity of the estimated vertical body center of mass acceleration to erroneous identifications of MIMU positions in the anteroposterior (AP), mediolateral (ML), and vertical (V) directions, expressed in percentage of the total variance of the estimation accuracy.

Assessment of postural instability in Parkinson\u2019s disease patients

BackgroundParkinson’s disease (PD) is a degenerative, progressive, neurological condition that influences the control of a person’s body movements. Computerized dynamic posturography (CDP) is a clinical tool intended to evaluate the integration of visual, vestibular, and somatosensory inputs to maintain postural gait. Posturography can be used to measure postural instability in PD patients. So, the aim of this study was to evaluate the postural control and elaborate on the pathophysiology of the balance impairment in PD patients in the “on” state.ResultsAll antero-posterior (AP) and medio-lateral (ML) sensory balance scores, except vestibular ones, were significantly lower in the study group compared to the control group. AP and ML sway were generally higher in the study group at all frequencies, with AP being mostly greater compared to ML sway in PD subjects. Global sensory scores were shown to deteriorate with increased durations of the disease and treatment.ConclusionsPD patients have higher postural instability in comparison to controls with AP sway being higher compared to ML.

Preoperative radiographic parameters in the case of using a narrow-version femoral implant in total knee arthroplasty.

Recently, total knee arthroplasty (TKA) designs that allow the use of narrow-version femoral implants have been introduced to avoid femoral overhang. The purpose of this study was to investigate the frequency of the use of narrow-version femoral implants and identify the difference in radiographic parameters between using a narrow-version femoral implant and a standard-version femoral implant in TKA. A retrospective study was conducted on 504 primary TKAs using a TKA system (Anthem or Persona) that allowed narrow-version femoral implants. Anteroposterior (AP) dimension, mediolateral (ML) dimension, and modified aspect percentage ratio (ML/AP dimension) of the distal femur in preoperative radiographs were compared between a standard-version group (n = 275) and a narrow-version group (n = 229). A cut-off value of a modified aspect percentage ratio indicating the need for a narrow-version femoral implant was determined using the receiver operating characteristic (ROC) curve. Mean ML dimension was 80.9 ± 6.1mm in the standard-version group and 77.3 ± 4.4mm in the narrow-version group (p < 0.001). Mean modified aspect percentage ratio was 138.8 ± 8.1% in the standard-version group and 131.7 ± 6.3% in the narrow-version group (p < 0.001). The optimum cut-off point of the modified aspect percentage ratio for narrow-version femoral implants was 135.4% (sensitivity: 72.0%; specificity: 66.7%) for Anthem and 133.3% (sensitivity: 75.9%, specificity: 76.4%) for Persona. In the narrow-version femoral implant group, the ML dimension and the mean modified aspect percentage ratio were smaller than in the standard-version femoral implant group. A smaller modified aspect percentage ratio of the distal femur in preoperative radiographs could predict the need for narrow-version femoral implants in TKA. It was suggested that the cut-off point could be suggested as 135.4% for Anthem TKA design and 133.3% for Persona TKA design. These radiographic parameters are cost-effective and easily applicable for planning a TKA.A smaller modified aspect percentage ratio of the distal femur in preoperative radiographs could predict the need for narrow-version femoral implants in TKA. The cut-off point was 135.4% for Anthem TKA design and 133.3% for Persona TKA design.

End of treatment cone-beam computed tomography (CBCT) is predictive of radiation response and overall survival in oropharyngeal squamous cell carcinoma

BackgroundImage guidance in radiation oncology has resulted in significant improvements in the accuracy and precision of radiation therapy (RT). Recently, the resolution and quality of cone beam computed tomography (CBCT) for image guidance has increased so that tumor masses and lymph nodes are readily detectable and measurable. During treatment of head and neck squamous cell carcinoma (HNSCC), on-board CBCT setup imaging is routinely obtained; however, this CBCT imaging data is not utilized to predict patient outcomes. Here, we analyzed whether changes in CBCT measurements obtained during a course of radiation therapy correlate with responses on routine 3-month follow-up diagnostic imaging and overall survival (OS).Materials/methodsPatients with oropharyngeal primary tumors who received radiation therapy between 2015 and 2018 were included. Anatomical measurements were collected of largest nodal conglomerate (LNC) at CT simulation, end of radiation treatment (EOT CBCT), and routine 3-month post-RT imaging. At each timepoint anteroposterior (AP), mediolateral (ML) and craniocaudal (CC) measurements were obtained and used to create a 2-dimensional (2D) maximum.ResultsCBCT data from 64 node positive patients were analyzed. The largest nodal 2D maximum and CC measurements on EOT CBCT showed a statistically significant correlation with complete response on 3-month post-RT imaging (r = 0.313, p = 0.02 and r = 0.318, p = 0.02, respectively). Furthermore, patients who experienced a 30% or greater reduction in the CC dimension had improved OS (Binary Chi-Square HR 4.85, p = 0.028).ConclusionDecreased size of pathologic lymph nodes measured using CBCT setup imaging during a radiation course correlates with long term therapeutic response and overall survival of HNSCC patients. These results indicate that CBCT setup imaging may have utility as an early predictor of treatment response in oropharyngeal HNSCC.

Proof-of-Concept of the Virtual Reality Comprehensive Balance Assessment and Training for Sensory Organization of Dynamic Postural Control.

Accurate quantification of the impact of visual, somatosensory, and vestibular systems on postural control may inform tailor-made balance intervention strategies. The aim of this proof-of-concept study was to determine the safety, sense of presence, system usability, and face validity of a newly developed Virtual Reality Comprehensive Balance Assessment and Training (VR-ComBAT) in healthy young individuals. The VR-ComBAT included six balance condition: (1) stable surface with fixed virtual reality (VR) surroundings; (2) stable surface with blacked out VR surroundings; (3) stable surface with VR visual conflict; (4) unstable surface with fixed VR surroundings; (5) unstable surface with blacked out VR surroundings; and (6) unstable surface with VR visual conflict. Safety was evaluated using the number of adverse events, including scores on the Simulator Sickness Questionnaire. Sense of presence was evaluated using the igroup Presence Questionnaire (iPQ). System usability was assessed using the Systems Usability Scale (SUS). Friedman analyses with post hoc Wilcoxon Signed Rank tests were employed to demonstrate face validity by quantifying center of pressure (COP) changes in mean distance, mean velocity, and mean frequency in the anteroposterior (AP) and mediolateral (ML) direction across the six conditions. Twenty-three participants (27.4 ± 8.0 years old; 13 women) reported no adverse events. Participants scores on average 44.9 ± 9.6 on the iPQ and 79.7 ± 9.9 on the SUS. Post hoc analyses showed significant changes in COP-based measures when compared to baseline. The mean frequency change of COP showed direction-dependence in which increased frequency change in AP was observed while decreased change in ML was noted. The VR-ComBAT provides a safe, feasible, and cost-effective VR environment that demonstrates consistent sensory re-weighting between visual, somatosensory, and vestibular systems. Future studies should investigate whether VR-ComBAT can be used to inform precision rehabilitation of balance and fall prevention in older adults without and with neurological conditions.

TEST–RETEST RELIABILITY OF STATIC POSTURAL BALANCE VARIABLES IN NATURAL AND FEET-TOGETHER STANCE CONDITIONS

It is important to confirm the reliability of postural balance variables because the results of balance tests would be different with different balance test protocols, i.e., stance conditions such as natural and feet-together stances. The aim of this study was to investigate the test–retest reliability of postural balance variables during the natural and feet-together stance conditions. Sixteen young healthy adults were instructed to sustain their center of body mass as stably as possible on the force plate. As balance standing conditions, natural (a comfortable self-selected stance width) and feet-together stances (placing the feet [Formula: see text] apart) were selected. The mean distance, mean velocity, mean frequency, and 95% confidence ellipse area were derived from the center of pressure (COP) time series in the overall, anteroposterior (AP), and mediolateral (ML) directions. To evaluate the test–retest reliability of the postural balance variables, Cronbach’s alpha coefficient was calculated in each stance condition. Mean velocity was the most reliable variable particularly in three repeated balances within both the natural and feet together stances ([Formula: see text]–0.921). The reliability of all variables of the three balance test was greater than that of the two balance tests, mainly in the natural stance. In contrast, the mean ML distance of the feet-together stance had poor reliability despite three balance tests ([Formula: see text]). These results suggest that the balance test protocol should consider the appropriate stance conditions as well as the number of balance trials to select the reliable postural balance variables.

Systematically Increased External Loads Secured Inferior to Younger and Older Adults’ Center of Mass Improves Postural Control without Compromising Functional Motor Performance

Few studies have investigated the effect of external loads secured inferior to the center of mass (COM) on postural control and motor performance in younger and older adults. In the present study, we investigated the effect of systematically increased external loads secured inferior to the COM on young (N = 15, age [years]: M = 26.67, SD= 3.45) and older adults’ (N = 15, age [years]: M = 67.4, SD= 7.69) center of pressure displacement and velocity, and also dart throwing performance in four different load conditions: 1) no load (control condition), 2) loading with 5% of body mass, 3) loading with 10% of body mass, and 4) loading with 20% of body mass. Overall, older adults had higher COP displacement and velocity in both anterior/posterior (AP) and Medio-lateral (ML) directions and poorer dart throwing scores than younger adults. Despite no significant difference in dart throwing performance for the different load conditions within each age group, loading with 10% and 20% of body mass reduced AP COP displacement relative to control for both study groups, with 20% body mass also reducing AP COP velocity relative to control for both study groups. In conclusion the present findings reveal that external loads secured inferior to older and younger adults’ COM may enhance postural control without compromising motor performance. The findings were discussed in the context of fall-prevention and athletic performance.

The Effects of Exergaming on Sensory Reweighting and Mediolateral Stability of Women Aged Over 60: Usability Study.

BackgroundOlder adults tend to experience difficulties in switching quickly between various reliable sensory inputs, which ultimately may contribute to an increased risk of falls and injuries. Sideward falls are the most frequent cause of hip fractures among older adults. Recently, exergame programs have been confirmed as beneficial tools for enhancing postural control, which can reduce the risk of falls. However, studies to explore more precisely which mechanism of exergaming directly influences older women’s ability to balance are still needed.ObjectiveOur aim was to evaluate, in a single-group pretest/posttest/follow-up usability study, whether Kinect exergame balance training might have a beneficial impact on the sensory reweighting in women aged over 60.MethodsA total of 14 healthy women (mean age 69.57 [SD 4.66] years, mean body mass index 26.21 [SD 2.6] kg/m2) participated in the study. The volunteers trained with the commercially available games of Kinect for Xbox 360 console 3 times (30 minutes/session) a week over a 6-week period (total of 18 visits). Participants’ postural sway in both the anteroposterior (AP) and mediolateral (ML) directions was recorded with NeuroCom Balance Master 6.0. To assess and measure postural sensory reweighting, the Modified Clinical Test of Sensory Interaction in Balance was used, where volunteers were exposed to various changes in visual (eyes open or eyes closed) and surface conditions (firm or foam surface).ResultsIn the ML direction, the Kinect exergame training caused a significant decrease in the sway path on the firm surface with the eyes open (P<.001) and eyes closed (P=.001), and on the foam surface with the eyes open (P=.001) and eyes closed (P<.001) conditions compared with baseline data. The follow-up measurements when compared with the baseline data showed a significant change in the sway path on the firm surface with the eyes open (P<.001) and eyes closed (P<.001) conditions, as well as on the foam surface with the eyes open (P=.003) and eyes closed (P<.001) conditions. Besides, on the firm surface, there were no significant differences in sway path values in the AP direction between the baseline and the posttraining measurements (eyes open: P=.49; eyes closed: P=.18). Likewise, on the foam surface, there were no significant differences in sway path values in the AP direction under both eyes open (P=.24) and eyes closed (P=.84) conditions.ConclusionsThe improved posturography measurements of the sway path in the ML direction might suggest that the Kinect exergame balance training may have effects on sensory reweighting, and thus on the balance of women aged over 60. Based on these results, Kinect exergaming may provide a safe and potentially useful tool for improving postural stability in the crucial ML direction, and thus it may help reduce the risk of falling.

Acute effects of proprioceptive neuromuscular facilitation exercises on the postural strategy in patients with chronic low back pain

IntroductionActive treatments focused on improvement in motor function are postulated in chronic low back patients (CLBP). Objectiveto establish the acute effects of PNF exercise on the postural control strategy. MethodsThe sway of the body was tested before intervention in fifty-three CLBP patients and after that participants were randomly assigned into the intervention PNF group (n = 25).Mean velocity (VEL) and sample entropy (SEn), over the center of pressure in the mediolateral (ML) and anterior-posterior (AP) planes served to estimate the postural strategy and automaticity levels in the neuromuscular controller. Tandem and one-leg standing tests (OLST) with eyes open and eyes closed were used. ResultsPain intensity decreased after the intervention. The VEL was no longer vision-dependent in both planes. The SEn decreased immediately after the exercise and either returned to or even exceeded the baseline values in the OLST ML plane. ConclusionA single session of PNF exercise may have a beneficial effect on pain and postural control in CLBP patients. The statistically significant pain relief combined with newly acquired better control of posture may have encouraged the PNF group participants to a subconscious exploration of the stability area. Postural movements were more automatized in OLST in the delayed test.

Video game and motor-cognitive dual-task training could be suitable treatments to improve dual-task interference in older adults

The objective of study was to investigate the effects of video game training in comparison with traditional motor-cognitive dual-task training on dual-task interference in older adults. Sixty older adults were allocated to the video game (intervention group) or the motor-cognitive dual-task training (control group). The outcome measures were dual-task cost (DTC) of linear metrics (Standard deviation (SD) of amplitude and velocity) and DTC of nonlinear metrics (approximate entropy, Lyapunov and correlation dimension) acquired from postural sway time series from both the mediolateral (ML) and anteroposterior (AP) directions. The results revealed in both groups, dual-task cost of SD of amplitude and velocity as well as Lyapunov were significantly decreased in post-training and follow-up compared with pre-training (p < 0.017), while there was no significant difference between the groups. Video game and motor-cognitive dual-task training could be recommended as suitable treatments to improve dual-task interference.

Gender Differences in the Morphological Characteristics of the Nasopalatine Canal and the Anterior Maxillary Bone - CBCT Study

Abstract The aim of this study was to investigate the gender differences in anatomical and morphometric characteristics of the nasopalatine canal–NPC and horizontal dimensions of the anterior maxilla by CBCT, which could be of interest for clinicians who perform implant surgery in this region. A retrospective quantitative study was conducted using CBCT images from the radiological database of the Department of Dentistry (Kragujevac) on a total of 113 participants (63 male and 50 female). The results of our study confirmed no gender difference in the distribution of NPC type, while the most frequent NPC type confirmed gender variations (cylindrical in females, funnel in males), but the lowest incidence of NPC type in both males and females was banana-type. The NPC length was significantly increased in males with no significant gender impact on medio-lateral (M-L) and antero-posterior (A-P) dimensions of the incisive foramen, as well as the A-P dimension of the nasal foramen. Linear regression analysis revealed the significant correlation between the M-L dimension of incisive foramen and the anterior maxilla diameter at all bone levels for males, and between the NPC length and the anterior maxilla diameter only in females at the level D. Also, both NPC type and gender significantly affected the correlations between the estimated parameters (females showed significant correlation only in funnel NPC type at the level D, while males showed significant correlation in both funnel NPC type at the level A, but also in hourglass-type at the level D). Those results imply significant gender impact in planning of various surgical interventions in the anterior maxilla region.

Postural and Head Control Given Different Environmental Contexts.

Virtual reality allows for testing of multisensory integration for balance using portable Head Mounted Displays (HMDs). HMDs provide head kinematics data while showing a moving scene when participants are not. Are HMDs useful to investigate postural control? We used an HMD to investigate postural sway and head kinematics changes in response to auditory and visual perturbations and whether this response varies by context. We tested 25 healthy adults, and a small sample of people with diverse monaural hearing (n = 7), or unilateral vestibular dysfunction (n = 7). Participants stood naturally on a stable force-plate and looked at 2 environments via the Oculus Rift (abstract “stars;” busy “street”) with 3 visual and auditory levels (static, “low,” “high”). We quantified medio-lateral (ML) and anterior-posterior (AP) postural sway path from the center-of-pressure data and ML, AP, pitch, yaw and roll head path from the headset. We found no difference between the different combinations of “low” and “high” visuals and sounds. We then combined all perturbations data into “dynamic” and compared it to the static level. The increase in path between “static” and “dynamic” was significantly larger in the city environment for: Postural sway ML, Head ML, AP, pitch and roll. The majority of the vestibular group moved more than controls, particularly around the head, when the scenes, especially the city, were dynamic. Several patients with monaural hearing performed similar to controls whereas others, particularly older participants, performed worse. In conclusion, responses to sensory perturbations are magnified around the head. Significant differences in performance between environments support the importance of context in sensory integration. Future studies should further investigate the sensitivity of head kinematics to diagnose vestibular disorders and the implications of aging with hearing loss to postural control. Balance assessment and rehabilitation should be conducted in different environmental contexts.

Kinematic Analysis of Dance-Based Exergaming: A Cross-Sectional Study.

Recent studies demonstrate improvements in both postural stability and mobility among aging populations and those with stroke who are exposed to dance-based exergaming (DBExG). However, age-related deficits and aging with cortical pathology may lead to distinct movement adaptation patterns during DBExG, which could impact therapeutic outcomes.<br/> Aim: The aim of this study was to examine the movement kinematics (postural stability and mobility) of healthy older adults, older adults with stroke, and young adults for different paces of dance during DBExG.<br/> Method: The study included 33 particpants (11 participant from each group of healthy older adults, older adults with chronic stroke, and healthy young adults) who performed the DBExG using slow- (SP), medium- (MP), and fast-paced (FP) songs with movements in the anteroposterior (AP) and mediolateral (ML) directions. Center of mass (CoM) sway area, excursion (Ex), and peaks as well as hip, knee, and ankle joint excursions were computed.<br/> Results: Results of the study revealed that CoM sway areas and Exs were greater for healthy young adults than for older adults with stroke for the SP dance (p < 0.05) and that there were significantly more AP CoM peaks for young adults than for healthy older adults and those with stroke for the FP dance (p < 0.05). Young adults also exhibited greater hip and ankle Exs than older adults with stroke (p < 0.05) for all song paces. Similarly, knee and ankle Exs were greater for healthy older adults than for older adults with stroke for all song paces (p < 0.05).<br/> Conclusion: The quantitative evaluation and comparison of the movement patterns presented for the three groups could provide a foundation for both assessing and designing therapeutic DBExG protocols for these populations.

The effect of video game-based training on postural control during gait initiation in community-dwelling older adults: a randomized controlled trial

Purpose The aim was to investigate the effect of video game training as compared to dual-task training on gait initiation (GI) which is a sensitive indicator of balance deficiency in older adults. Method Sixty-six older adults were allocated to the video game-based training (intervention group) or the motor-cognitive dual-task training (active control group). The outcome measures were the mediolateral (ML)/anteroposterior (AP) displacement and velocity of COP during the phases of GI (anticipatory, weight transition, and locomotor). Results The results indicated in the anticipatory phase, the ML & AP COP displacement were significantly increased at post-training relative to pre-training across both groups (p < 0.041). In the weight transition phase, the AP COP displacement & ML COP velocity were significantly increased at post-training than pre-training (p < 0.032). However, in the locomotor phase, within the intervention group, the ML COP displacement & ML COP velocity were significantly increased at follow-up as compared to pre-training (p < 0.05), while no such differences were observed within the control group. Conclusion Both treatments were effective in improving COP trajectory during the phases of anticipatory and weight transition, while the intervention group was more effective during the phase of locomotor. So, these treatments can be recommended for clinical settings. Implications for rehabilitation The video game and dual task training were effective in improving COP trajectory during the phases of anticipatory and weight transition. The video game-based training was more effective during the phase of locomotor. The study findings could have useful implications to further introduce cognition-based rehabilitation programs such as video games for older adults. Rehabilitation professionals could use the video game to improve the postural control of older adults.

The effect of age, sex and a firm-textured surface on postural control

In previous studies, the influence of plantar sensation has been examined using various textured surfaces with different stiffness materials to assess static balance. This study investigated the effects of a Firm Textured Surface (FTS) along with age and sex-related influences on postural control under different visual conditions. Forty subjects (20 elderly, 10 males, mean age 68.30, 10 females, mean age 68.00, and 20 young people, 10 males, mean age 25.45, 10 females, mean age 27.30) participated in this study maintained a quiet standing on FTS, foam and firm surfaces with eyes open and closed. The center of pressure displacement (CoPDISP), CoP velocity (CoPVEL), and sway velocity of the CoP in anteroposterior (AP) and mediolateral (ML) direction (VA/P and VM/L) were measured. FTS was associated with lower postural sway measures in both the groups with eyes open and closed. However, the foam surface showed the worst results in all postural parameters under all experimental conditions. Separate four-way ANOVAs were applied to each dependent variable. The main effects of surface (p < 0.0001), vision (p < 0.0001) and age (p < 0.0001 for CoPDISP, CoPVEL and VA/P; p = 0.0003 for VM/L) were significant in each of the four fitted models. Sex was never significant, either as a main effect or an interaction with other experimental factors. Eyes open were able to reduce the negative effects of the foam surfaces but without vision the proprioceptive sensory system cues of the body state become more important for maintaining balance. A good stimulation with rigid texture should be considered as relief to reduce the physiological-related decline of afferent information with age.

Optimal Frequency and Amplitude of Vertical Viewpoint Oscillation for Improving Vection Strength and Reducing Neural Constrains on Gait.

Inducing self-motion illusions referred as vection are critical for improving the sensation of walking in virtual environments (VE). Adding viewpoint oscillations to a constant forward velocity in VE is effective for improving vection strength under static conditions. However, the effects of oscillation frequency and amplitude on vection strength under treadmill walking conditions are still unclear. Besides, due to the visuomotor entrainment mechanism, these visual oscillations would affect gait patterns and be detrimental for achieving natural walking if not properly designed. This study was aimed at determining the optimal frequency and amplitude of vertical viewpoint oscillations for improving vection strength and reducing gait constraints. Seven subjects walked on a treadmill while watching a visual scene. The visual scene presented a constant forward velocity equal to the treadmill velocity with different vertical viewpoint oscillations added. Five oscillation patterns with different combinations of frequency and amplitude were tested. Subjects gave verbal ratings of vection strength. The mediolateral (M-L) center of pressure (CoP) complexity was calculated to indicate gait constraints. After the experiment, subjects were asked to give the best and the worst oscillation pattern based on their walking experience. The oscillation frequency and amplitude had strong positive correlations with vection strength. The M-L CoP complexity was reduced under oscillations with low frequency. The medium oscillation amplitude had greater M-L CoP complexity than the small and large amplitude. Besides, subjects preferred those oscillation patterns with large gait complexity. We suggested that the oscillation amplitude with largest M-L CoP complexity should first be chosen to reduce gait constraints. Then, increasing the oscillation frequency to improve vection strength until individual preference or the boundary of motion sickness. These findings provide important guidelines to promote the sensation of natural walking in VE.

Evaluation of set-up errors and estimation of set-up margin during external beam radiation therapy of prostate cancer using electronic portal imaging device (EPID)

AbstractAim:In radiation therapy, accurate dose distribution in target volume requires accurate treatment setup. The set-up errors are unwanted and inherent in the treatment process. By achieving these errors, a set-up margin (SM) of clinical target volume (CTV) to planning target volume (PTV) can be determined. In the current study, systematic and random set-up errors that occurred during prostate cancer radiotherapy were measured by an electronic portal imaging device (EPID). The obtained values were used to propose the optimum CTV-to-PTV margin in prostate cancer radiotherapy.Materials and methods:A total of 21 patients with prostate cancer treated with external beam radiation therapy (EBRT) participated in this study. A total of 280 portal images were acquired during 12 months. Gross, population systematic (Σ) and random (σ) errors were obtained based on the portal images in Anterior–Posterior (AP), Medio-Lateral (ML) and Superior–Inferior (SI) directions. The SM of CTV to PTV were then calculated and compared by using the formulas presented by the International Commission on Radiation Units and Measurements (ICRU) 62, Stroom and Heijmen and Van Herk et al.Results:The findings showed that the population systematic errors during prostate cancer radiotherapy in AP, ML and SI directions were 1·40, 1·95 and 1·94 mm, respectively. The population random errors in AP, ML and SI directions were 2·09, 1·85 and 2·29 mm, respectively. The SM of CTV to PTV calculated in accordance with the formula of ICRU 62 in AP, ML and SI directions were 2·51, 2·68 and 3·00 mm, respectively. And according to Stroom and Heijmen, formula were 4·23, 5·19 and 5·48 mm, respectively. And Van Herk et al. formula were 4·96, 6·17 and 6·45 mm, respectively.Findings:The SM of CTV to PTV in all directions, based on the formulas of ICRU 62, Stroom and Heijmen and van Herk et al., were equal to 2·73, 4·98 and 5·86 mm, respectively; these values were obtained by averaging the margins in all directions.

The effect of low light levels on postural stability in older adults with age-related macular degeneration.

To investigate the effect of low light levels on postural stability in older adults with and without age-related macular degeneration (AMD). Participants included 28 older adults [14 with AMD (mean age ± S.D., 83.4±6.7years) and 14 controls with normal vision (74.6±3.3years)]. Postural stability was assessed with eyes open on both a firm and foam surface under four lighting conditions in a randomised order: photopic (~436lux, vertically at the eye), sudden reduction to mesopic (~436 to ~1lux), adapted mesopic (~1lux) and adapted mesopic with a light emitting diode (LED) door frame lighting system (~1.3lux), using the root mean square (RMS) of the centre of pressure measures derived from an electronic force plate in the anterior-posterior (AP) and medio-lateral (ML) directions. Visual function was assessed binocularly (visual acuity, contrast sensitivity and visual fields), physical function was assessed using standardised measures (sit-to-stand, grip strength and the timed walk test) and self-reported difficulties under low light levels were recorded using the Low Luminance Questionnaire. Data were analysed using linear mixed models. For all participants, low light levels significantly increased postural sway on the foam surface in the AP (p=0.01) but not ML (p=0.80) direction, but had no effect on postural stability on the firm surface. On the foam surface, while AP-RMS sway was significantly greater in the sudden (p<0.001) and adapted (p=0.02) mesopic compared to the photopic condition, sway for the adapted mesopic with the LED lighting system was not significantly different to the photopic condition (p=0.20). On the foam surface, AP-RMS (p=0.02) and ML-RMS (p<0.001) sway were significantly greater in the AMD compared to the control group. None of the measures of visual function was significantly associated with AP- or ML-RMS sway. On the foam surface, low light levels significantly reduced postural stability in older adults with and without AMD, and postural stability was significantly reduced for the AMD group compared to controls, regardless of light level. Importantly, the LED lighting system reduced sway under mesopic conditions, which was not significantly greater than that measured under photopic conditions in either group. These findings have important implications for enhancing the visual environment for older adults with and without AMD to improve postural stability and reduce the risk of falls in low lighting environments.

Reliability of IMU-Derived Static Balance Parameters in Neurological Diseases.

Static balance is a commonly used health measure in clinical practice. Usually, static balance parameters are assessed via force plates or, more recently, with inertial measurement units (IMUs). Multiple parameters have been developed over the years to compare patient groups and understand changes over time. However, the day-to-day variability of these parameters using IMUs has not yet been tested in a neurogeriatric cohort. The aim of the study was to examine day-to-day variability of static balance parameters of five experimental conditions in a cohort of neurogeriatric patients using data extracted from a lower back-worn IMU. A group of 41 neurogeriatric participants (age: 78 ± 5 years) underwent static balance assessment on two occasions 12–24 h apart. Participants performed a side-by-side stance, a semi-tandem stance, a tandem stance on hard ground with eyes open, and a semi-tandem assessment on a soft surface with eyes open and closed for 30 s each. The intra-class correlation coefficient (two-way random, average of the k raters’ measurements, ICC2, k) and minimal detectable change at a 95% confidence level (MDC95%) were calculated for the sway area, velocity, acceleration, jerk, and frequency. Velocity, acceleration, and jerk were calculated in both anterior-posterior (AP) and medio-lateral (ML) directions. Nine to 41 participants could successfully perform the respective balance tasks. Considering all conditions, acceleration-related parameters in the AP and ML directions gave the highest ICC results. The MDC95% values for all parameters ranged from 39% to 220%, with frequency being the most consistent with values of 39–57%, followed by acceleration in the ML (43–55%) and AP direction (54–77%). The present results show moderate to poor ICC and MDC values for IMU-based static balance assessment in neurogeriatric patients. This suggests a limited reliability of these tasks and parameters, which should induce a careful selection of potential clinically relevant parameters.