Center Of Pressure Research Articles

Effects of arousal and valence on center of pressure and ankle muscle activity during quiet standing.

Emotion affects postural control during quiet standing. Emotional states can be defined as two-dimensional models comprising valence (pleasant/unpleasant) and arousal (aroused/calm). Most previous studies have investigated the effects of valence on postural control without considering arousal. In addition, studies have focused on the center of pressure (COP) trajectory to examine emotional effects on the quiet standing control; however, the relationship between neuromuscular mechanisms and the emotionally affected quiet standing control is largely unknown. This study aimed to investigate the effects of arousal and valence on the COP trajectory and ankle muscle activity during quiet standing. Twenty-two participants were instructed to stand on a force platform and look at affective pictures for 72 seconds. The tasks were repeated six times, according to the picture conditions composed of arousal (High and Low) and valence (Pleasant, Neutral, and Unpleasant). During the task, the COP, electromyogram (EMG) of the tibialis anterior and soleus muscles, and electrocardiogram (ECG) were recorded. The heart rate calculated from the ECG was significantly affected by valence; the value was lower in Unpleasant than that in Neutral and Pleasant. The 95% confidence ellipse area and standard deviation of COP in the anterior-posterior direction were lower, and the mean power frequency of COP in the anterior-posterior direction was higher in Unpleasant than in Pleasant. Although the mean velocity of the COP in the medio-lateral direction was significantly lower in Unpleasant than in Pleasant, the effect was observed only when arousal was low. Although the EMG variables were not significantly affected by emotional conditions, some EMG variables were significantly correlated with the COP variables that were affected by emotional conditions. Therefore, ankle muscle activity may be partially associated with postural changes triggered by emotional intervention. In conclusion, both valence and arousal affect the COP variables, and ankle muscle activity may be partially associated with these COP changes.

Dynamics of Center of Pressure Trajectory in Gait: Unilateral Transfemoral Amputees Versus Non-Disabled Individuals.

The primary goal of rehabilitation for individuals with lower limb amputation, particularly those with unilateral transfemoral amputation (uTFA), is to restore their ability to walk independently. Effective control of the center of pressure (COP) during gait is vital for maintaining balance and stability, yet it poses a significant challenge for individuals with uTFA. This study aims to study the COP during gait in individuals with uTFA and elucidate their unique compensatory strategies. This study involved 12 uTFA participants and age-matched non-disabled controls, with gait and COP trajectory data collected using an instrumented treadmill. Gait and COP parameters between the control limb (CL), prosthetic limb (PL), and intact limb (IL) were compared. Notably, the mediolateral displacement of COP in PL exhibited significant lateral displacement compared to the CL from 30% to 60% of the stance. In 20% to 45% of the stance, the COP forward speed of PL was significantly higher than that of the IL. Furthermore, during the initial 20% of the stance, the vertical ground reaction force of PL was significantly lower than that of IL. Additionally, individuals with uTFA exhibited a distinct gait pattern with altered duration of loading response, single limb support, pre-swing and swing phases, and step time. These findings indicate the adaptability of individuals with uTFA in weight transfer, balance control, and pressure distribution on gait stability. In conclusion, this study provides valuable insights into the unique gait dynamics and balance strategies of uTFA patients, highlighting the importance of optimizing prosthetic design, alignment procedures, and rehabilitation programs to enhance gait patterns and reduce the risk of injuries due to compensatory movements.

Postural Sway Characteristics in Static Balance Control of Youth Female Soccer Players

Purpose: Balance control, particularly in uni-lateral domain, is essential in soccer. Majority of the existing studies examined dynamic balance via clinical tools, and primarily involved male players. Thus, the purpose here was to examine the nature of Center of Pressure (COP) postural sway in youth female players across bipedal and unipedal conditions Methods: Sixteen pre-adolescent female competitive players (age 12.4±21.40 years) were asked to stand on a force plate in bi-pedal stance with the dominant and non-dominant legs respectively. Three, 10 second trials were carried out for each condition. Results: As expected, across the four COP measures bi-pedal stance resulted in least sway (P= .05). However, the subsequent analysis showed different center of pressure (COP) profiles in the dominant versus non-dominant condition across COP velocity (P= .003), path length (P= .001) and anterior-posterior (AP) sway (P= .003), with sway area revealing no statistical differences (P= .821). In addition, the analysis of stabilograms confirmed that in the non-dominant condition the pronounced COP oscillations were of lower amplitude and frequency as compared to the dominant leg. Conclusions: Overall, postural asymmetry was found as the sway characteristics on both legs differed, with dominant side exhibiting more sway and faster COP oscillations. In line with the inverted pendulum model, this may be due to less than optimal ability to modulate muscle torques generated at the ankle. It is hypothesized that the postural asymmetry between the dominant and non-dominant legs may result from muscular asymmetries that have been often reported in youth soccer players, as a result of their pronounced foot dominance.

A Computer-Aided Screening Solution for the Identification of Diabetic Neuropathy from Standing Balance by Leveraging Multi-Domain Features.

The early diagnosis of diabetic neuropathy (DN) is fundamental in order to enact timely therapeutic strategies for limiting disease progression. In this work, we explored the suitability of standing balance task for identifying the presence of DN. Further, we proposed two diagnosis pathways in order to succeed in distinguishing between different stages of the disease. We considered a cohort of non-neuropathic (NN), asymptomatic neuropathic (AN), and symptomatic neuropathic (SN) diabetic patients. From the center of pressure (COP), a series of features belonging to different description domains were extracted. In order to exploit the whole information retrievable from COP, a majority voting ensemble was applied to the output of classifiers trained separately on different COP components. The ensemble of kNN classifiers provided over 86% accuracy for the first diagnosis pathway, made by a 3-class classification task for distinguishing between NN, AN, and SN patients. The second pathway offered higher performances, with over 97% accuracy in identifying patients with symptomatic and asymptomatic neuropathy. Notably, in the last case, no asymptomatic patient went undetected. This work showed that properly leveraging all the information that can be mined from COP trajectory recorded during standing balance is effective for achieving reliable DN identification. This work is a step toward a clinical tool for neuropathy diagnosis, also in the early stages of the disease.

Is a portable pressure plate an alternative to force plates for measuring postural stability and interlimb coordination of quiet standing balance control?

Center-of-pressure (COP) synchronization and symmetry can inform adaptations in balance control following one-sided sensorimotor impairments (e.g., stroke). As established force plates are impossible to transport, we aimed to criterion validate a portable pressure plate for obtaining reliable COP synchronization and symmetry measures, next to conventional postural stability measures. Twenty healthy adults participated. In a single session, three 40-s eyes-open and eyes-closed quiet stance trials were performed per plate-type, randomly ordered. Individual-limb COPs were measured to calculate between-limb synchronization (BLS) and dynamic control asymmetry (DCA). Net COP (i.e., limbs combined) area, amplitude, and velocity were used to describe anteroposterior (AP) and mediolateral (ML) postural stability. Criterion validity was evaluated using Spearman correlations (r) and Bland-Altman plots. Test-retest reliability was tested using intraclass correlation coefficients (ICC). Strong correlations (r > 0.75) and acceptable reliability (ICC > 0.80) were found regarding individual-limb COP velocity and DCA, net COP ML amplitude and AP and ML velocities. Bland-Altman plots yielded possible proportional bias; the pressure plate systematically underestimated COP scores by force plates and a larger error associated with a larger measurement. Despite correlations between instruments and sufficient reliability for measuring postural stability and DCA, this technical note strongly suggests, due to a systematic deviation, using the same plate-type to accurately assess performance change within subjects longitudinally over time.

Investigating the Effect of Addition of Cervical Proprioceptive Training to Conventional Physiotherapy on Visual, Vestibular and Proprioceptive Dependency of Postural Control in Patients with Chronic Non-Specific Neck Pain: A Randomized Controlled Clinical Trial.

While cervical proprioception deficit has been suggested as a contributing factor to clinical consequences of chronic non-specific neck pain (CNSNP), the effect of addressing such impairments on postural control strategies has remained unexplored. The aim of this study was to compare the response of the postural control system to alteration of sensory afferents in CNSNP with asymptomatic individuals. Furthermore, we examined whether proprioceptive training would yield superior outcomes to routine physiotherapy for improvement of postural control, pain and disability. Center of pressure (CoP) variables of sixty CNSNP patients equally distributed in any of the proprioception-specific or conventional physiotherapy groups and 30 asymptomatic participants were evaluated under four standing conditions:1) normal, 2) foam, 3) cervical extension/eyes open and 4) cervical extension/eyes closed standing. CoP anteroposterior range and anteroposterior and mediolateral velocity in patients were significantly higher than the control group under condition 2 (P<0.05). Patients also demonstrated lower anteroposterior lyapunov exponent under conditions 2 and 4 (P<0.05). Both interventions significantly decreased anteroposterior range and anteroposterior velocity(P<0.05). Anteroposterior lyapunov exponent also increased under condition 2 (P<0.05).. After the interventions, CoP anteroposterior range and anteroposterior velocity were significantly lower in the proprioceptive exercise group than the conventional physiotherapy group (P<0.05). Anteroposterior lyapunov exponent was also significantly higher in the proprioceptive exercise group (P<0.05).This while there was no significant difference between these patients and control group participants in any of the CoP variables after intervention. Our results rejected the hypothesis that impaired neck proprioception in the presence of CNSNP is compensated by overweighting other sources of sensory afferent information. The findings also revealed that while proprioceptive exercises successfully returned postural strategies of CNSNP patients to those in asymptomatic participants, they do not add to clinical recovery of these patients.

Comparing the Effects of 8-week Exercise Programs in the Sagittal and Frontal Planes on the Postural Sway of Elderly Men

Background and Aims Exercises are mostly used to control balance and reduce the risk of falling in the elderly. However, the effect of exercise in the frontal plane has been less studied. Therefore, this study aims to compare the effect of 8 week exercises in the sagittal and frontal planes on the postural sway of elderly men. Methods In this quasi-experimental study, 24 elderly males (Mean age: 67.21±1.56 years) were divided into two intervention groups of sagittal-plane and frontal-plane exercises. The exercises were performed for 8 weeks. The center of pressure (CoP) parameters in two groups before and after the intervention were evaluated using a foot scanner system. Finally, the ANCOVA was used for data analysis. P≤0.05 was considered statistically significant. Results The results showed a significant decrease in CoP perturbations in the Y-axis at the medial-lateral, anterior-posterior, and lateral-medial directions in the frontal plane group compared to the sagittal group (P&lt;0.05). Moreover, there was a significant decrease in the CoP area after perturbations at the medial-lateral, anterior-posterior, and lateral-medial directions in the frontal group compared to the sagittal group (P&lt;0.05). Conclusion It seems that exercises in the frontal plane can reduce postural sway in elderly men compared to sagittal-plane exercises. Therefore, it is recommended to emphasize the exercises of the hip abductor and adductor muscles in the frontal plane in designing exercise protocols for elderly men.

Stepping into emotions: investigating the effect of angry and fearful faces on forward stepping and quiet stance.

Facial expressions conveying an emotion may affect social interactions, such as approach- or avoidance-related behaviors. A specific facial feature is the gaze direction. An emotional facial expression such as anger will elicit distinct behavioral tendencies, depending on whether the angry gaze is directed toward the onlooker, or in a different direction. We tested whether facial expressions of anger and fear, combined with direct or averted gaze, elicit approach- or avoidance tendencies, using a go/no-go variant of the whole-body stepping task. Healthy adults stood on a force plate, recording the center of pressure (COP). Participants were presented with angry or fearful faces; either with direct or averted gaze. Participants had to identify the emotion, and "depending on instructions- either make a single step forward, or remain in a quiet stance. From the COP of the forward steps, we derived parameters such as reaction time and step size. From the quiet standing trials we derived parameters of postural sway, indicative of postural "freeze." We used analysis of variance to analyze the outcomes. First, we found that steps were initiated faster with angry faces than with fearful faces, in line with existing literature. Second, we did not observe a significant effect of gaze direction. Forward steps with direct and averted gaze had similar COP characteristics. Finally, we had expected to find freeze (postural immobility) with fearful faces, but this was also not observed. We discuss various explanations for the finding, and implications for research into the motoric grounding of social interactions.

An improved intermittent control model of postural sway during quiet standing implemented by a data driven approach

This paper proposes a new intermittent control model during human quiet standing, which is consisted of postulated “regular intervention” and “imminent intervention”. The regular intervention is within the main control loop, and its trigger condition is equivalent to the switching frequency of center of pressure (COP) data calculated by wavelet transform. The imminent intervention will only be triggered after the postural sway angle exceeds a certain threshold. In order to prove the effectiveness of the new model, the simulation results of the new model and the model proposed by Asai et al. (2009) are compared with the experimental data. The setting parameters of both models are retrieved by Bayesian regression from the experimental data. The results show that the new model not only could exhibit two power law scaling regimes of power spectral density (PSD) of COP, but also show that indices of the probability density function distance, root mean square (RMS), Total Sway Path, displacement Range, 50% power frequency of center of mass (COP) between the simulation results and the experimental data are closer compared to the existing model. Moreover, the limit cycle oscillations (LCOs) obtained from the simulation results of the new model have a higher degree of matching with those retrieved from the experimental data.

Deep Learning Model to Evaluate Sensorimotor System Ability in Patients With Dizziness for Postural Control.

Balanced posture without dizziness is achieved via harmonious coordination of visual, vestibular, and somatosensory systems. Specific frequency bands of center of pressure (COP) signals during quiet standing are closely related to the sensory inputs of the sensorimotor system. In this study, we proposed a deep learning-based novel protocol using the COP signal frequencies to estimate the equilibrium score (ES), a sensory system contribution. Sensory organization test was performed with normal controls (n=125), patients with Meniere's disease (n=72) and vestibular neuritis (n=105). The COP signals preprocessed via filtering, detrending and augmenting during quiet standing were converted to frequency domains utilizing Short-time Fourier Transform. Four different types of CNN backbone including GoogleNet, ResNet-18, SqueezeNet, and VGG16 were trained and tested using the frequency transformed data of COP and the ES under conditions #2 to #6. Additionally, the 100 original output classes (1 to 100 ESs) were encoded into 50, 20, 10 and 5 sub-classes to improve the performance of the prediction model. Absolute difference between the measured and predicted ES was about 1.7 (ResNet-18 with encoding of 20 sub-classes). The average error of each sensory analysis calculated using the measured ES and predicted ES was approximately 1.0%. The results suggest that the sensory system contribution of patients with dizziness can be quantitatively assessed using only the COP signal from a single test of standing posture. This study has potential to reduce balance testing time (spent on six conditions with three trials each in sensory organization test) and the size of computerized dynamic posturography (movable visual surround and force plate), and helps achieve the widespread application of the balance assessment.

Moving from stable standing to single-limb stance or an up-on-the-toes position: The importance of vision to dynamic balance control.

Understanding the contribution vision has to dynamic balance control may help in understanding where/why loss of balance occurs during everyday locomotion. The current study determined how body-centre-of-mass (BCoM) dynamics and postural stability when moving to and holding a single-limb-stance (SS) or an up-on-the-toes (UTT) position were affected by visual occlusion. From standing on a force platform, 18 adults (mean (SD) 26.7 (4.8) years; 1.73 (0.08) m; 84.0 (22.9) kg; 7 females) completed repeated trials (x3) with and without vision in which they moved to either a SS or an UTT position (order countered-balanced), and attempted to hold that position for 2 (SS) or 5 (UTT) seconds before returning to standing. UTT trials were also repeated at a fast speed, and SS trials were repeated using both the dominant and non-dominant limb. BCoM dynamics were assessed by analysing the displacement and peak velocity of the centre-of-pressure (CoP) when moving to and from the SS and UTT positions. Balance stability was the variability in the CoP displacement/velocity when holding these positions. Results indicate that under visual occlusion, the peak CoP velocity when moving to the SS or UTT position was reduced (ES, 0.67 and 0.68, respectively), suggesting greater caution. Both the variability in the CoP displacement/velocity when holding these positions and the peak CoP velocity when returning to flat-standing increased (SS: ES, 1.0 and 0.86, respectively; UTT: ES 1.26 and 0.66, respectively), suggesting, respectively, greater instability and poorer control. The poorer control in SS trials, occurred when returning to standing from the SS position held on the non-dominant limb, and correspondingly, the reduction in SS duration when vision was occluded was greater for the non-dominant limb trails (limb-vision interaction; p = 0.042). This suggests that movements initiated/controlled by the non-dominant limb are more reliant on visual feedback than those initiated/controlled by the dominant limb.

Magnitude of changes in muscle endurance in the Biering-Sorensen test and changes in balance in subjects with LBP treated with muscle energy techniques.

Purpose: Manual therapy is used as a conservative treatment for people with low back pain (LBP). The scale of the problem encourages the search for the most effective methods to assess of manual treatment. Therefore, the aim of the study was to investigate magnitude of changes in muscle endurance using the Biering-Sorensen test (BST) and to analyse balance in patients with LBP treated with ERS and FRS muscle energy techniques (MET). Methods: The study included fifteen men with LBP (mean age: 42 years) working as automotive assemblers. Endurance of the biceps femoris (BF), gluteus maximus (GM) and erector spinae (ES) muscles were analysed using sEMG during the BST. The level of experienced pain, degree of disability and postural stability were also examined. Results before and after a three-week treatment cycle using MET were compared. Results: The MET therapy resulted in a reduction in pain ( p = 0.001), an improvement in the degree of disability ( p < 0.001) and an increase in the duration of the BST ( p < 0.001). After therapy, the values of the NMFs parameter indicating the degree of fatigue increased, i.e., ES muscle endurance increased, both right ( p = 0.004) and left ( p < 0.001). There was also a statistically significant decrease in the centre of pressure (COP) movement velocity in balance tests. Conclusions: The use of MET in patients with LBP increases muscle endurance, improves postural balance, and reduces pain levels on the VAS and disability levels according to the ODI. MET appears to be a good tool for preventing LBP.

Analysis of the Relation Between Balance Control Subsystems: A Structural Equation Modeling Approach.

Balance plays a crucial role in human life and social activities. Maintaining balance is a relatively complex process that requires the participation of various balance control subsystems (BCSes). However, previous studies have primarily focused on evaluating an individual's overall balance ability or the ability of each BCS in isolation, without considering how they influence (or interact with) each other. The first study used clinical scales to evaluate the functions of the four BCSes, namely Reactive Postural Control (RPC), Anticipatory Postural Adjustment (APA), Dynamic Gait (DG), and Sensory Orientation (SO), and psychological factors such as fear of falling (FOF). A hierarchical structural equation modeling (SEM) was used to investigate the relationship between the BCSes and their association with FOF. The second study involved using posturography to measure and extract parameters from the center of pressure (COP) signal. SEM with sparsity constraint was used to analyze the relationship between vision, proprioception, and vestibular sense on balance based on the extracted COP parameters. The first study revealed that the RPC, APA, DG and SO indirectly influenced each other through their overall balance ability, and their association with FOF was not the same. APA has the strongest association with FOF, while RPC has the least association with FOF. The second study revealed that sensory inputs, such as vision, proprioception, and vestibular sensing, directly affected each other, but their associations were not identical. Among them, proprioception plays the most important role in the three sensory subsystems. This study provides the first numerical evidence that the BCSes are not independent of each other and exist in direct or indirect interplay. This approach has important implications for the diagnosis and management of balance-related disorders in clinical settings and improving our understanding of the underlying mechanisms of balance control.

Immediate Effect of Wearable Balance Training Device on Muscle Co-Contraction and Postural Control During Standing.

Postural control is one of the primary body functions for fall prevention. Unexpected perturbation-based balance training is effective for improving postural control. However, the effect of perturbation-based training using assistive devices on muscle activity and co-contraction for standing balance is still unclear. This training is also difficult to perform easily because it requires large instruments or expert guidance. The purpose of this study is to demonstrate the effect of perturbation-based balance training using a wearable balance training device (WBTD) on postural control. In this study, fourteen healthy young adult males were assigned to either a WBTD group or a sham group. In the intervention session, participants in the WBTD group were perturbed either left or right direction at random timing by the WBTD during tandem stance balance training. Participants in the Sham group did not receive external perturbation during tandem stance balance training. Before and after the intervention session, participants of both groups underwent unexpected lateral perturbation postural control testing (pre- and post-test). The normalized integral of electromyography (IEMG), co-contraction index (CCI), and center of pressure (COP) parameters were measured in the pre- and post-test. Experimental results showed that the WBTD group in the post-test significantly decreased left Gluteus Medius IEMG, CCI of both Gluteus Medius, and peak [Formula: see text] velocity, compared to those of the pre-test ( [Formula: see text], p =0.024 , p =0.031 , respectively). We conclude that balance training using WBTD could improve flexible postural control adjustment via cooperative muscle activation.

The impact of external perturbations on postural control

Purpose External factors can disrupt postural control, but the intricate workings of the postural control system enable an appropriate response. This study seeks to assess how external perturbations affect postural control. Methods Twenty women participated in study, which consisted four trials involved quiet standing and experiencing induced perturbations by being struck with a boxing bag from the back, right, and left sides, respectively. The center of pressure (CoP) path length was recorded for each of the mentioned trials. Sample Entropy (SampEn), Lyapunov Exponent (LyE), and Fractal Dimension (FD) were computed for the CoP time series, separately for the anterior-posterior (AP) and mediolateral (ML) directions. The nonparametric Friedman ANOVA with Dunn-Bonferroni post-hoc analysis was employed to investigate the influence of external perturbations on both linear and nonlinear parameters on postural control. Results The post-hoc analysis showed for LyE_AP_quiet (1.02 ± 0.18) significantly higher values than for LyE_AP_right (0.92 ± 0.22) and significantly higher for LyE_AP_left. Lyapunov Exponent was the parameter that differentiated the most between samples. Conclusions The greatest number of significant differences between samples were demonstrated by the Lyapunov Exponent. This nonlinear parameter should be used to evaluate various perturbations during upright position in healthy subjects.

Moving together-benefits of a 12-week online dance training intervention on static and dynamic postural stability and gait speed in older women: an exploratory pre-post study.

Physical inactivity negatively affects gait performance and postural stability in older adults resulting in a higher risk of fall accidents. Previous research has shown that in-person dance training improves various aspects of balance and lower-extremity function, however, little is known about the potential benefits of dance training delivered online on variables used for fall risk stratification in older adults. We aimed to explore the benefits of a 12-week online dance training intervention on static and dynamic postural stability and gait speed in older women. Forty-five older adults (44 women) were included in this exploratory pre-post study. The 12-week dance intervention consisted of two weekly 60-min classes in contemporary (improvisation) and salsa dance delivered online through Zoom video calls. Static and dynamic postural stability was assessed using the center of pressure (CoP) area and velocity (force platform), and the Mini Balance Evaluation Systems Test (Mini-BESTest), respectively. 10-m gait speed was measured using photo gates. Before and after comparisons were performed using paired sample t-tests. Thirty-two older women completed the study. There were no significant changes for static postural stability assessed by CoP area or velocity (P ≥ 0.218, Cohen d ≤ 0.234). The Mini-BESTest total score was significantly improved at post-intervention (23.88 ± 3.01) compared to baseline (22.56 ± 1.41, P = 0.007, d = 0.52). 10-m gait speed was significantly faster at post-intervention (1.68 ± 0.25 m/s) compared to baseline (1.57 ± 0.22 m/s, P < 0.001, d = 0.737). Although some caution is needed due to the uncontrolled study design, the results indicate that online dance training has a small effect on static postural stability but may be beneficial for gait speed and in particular dynamic postural control among older women. While the absolute increase in gait speed suggests limited clinical relevance, the change in Mini-BESTest score may reflect a clinically meaningful enhancement of dynamic postural control.

Effectiveness of X-box Gaming on Balance using One Leg Standing among Older Adults: A Mini Systematic Review

Introduction: The predominant challenge encountered by the elderly and older people is balance. This concern is not only affecting the quality of life for individuals but increasing their risk of falling. Literatures available determined the effect of various gaming apparatus on balance in older adults but these evidences need to be reviewed systematically to determine their overall effect. There is no systematic review assessing the effectiveness of X-box gaming on balance among older adults. Aim: To assess X-box gaming effectiveness on older adults balance. Materials and Methods: Searches in PUBMED, Physiotherapy Evidence Database (PEDro), and SCOPUS (2015-2023) included randomised controlled trials featuring participants, aged more than 55 years, using one-legged stance test as outcome measure, as assessing one’s balance through single-leg standing on various surfaces aids in determining the Center of Pressure (CoP). Greater variability in CoP measurements suggests poor overall balance control and an elevated risk of falls among individual. X-box gaming interventions were included. Results: Initially, 432 studies were screened; after eliminating duplicates and applying inclusion criteria, 2 eligible studies were selected for review. Conclusion: The reviewed trials showed diverse X-box and exercise intervention parameters. Future research should explore different treatment protocols for balance re-education and exercise therapy in older adults to establish optimal guidelines for enhancing balance and reducing fall risk.

Wave-converging pressure increase in curved cylindrical rotating detonation combustors

The internal combustion structure of a curved cylindrical rotating detonation combustor (RDC) was experimentally investigated through optical observation and pressure measurements. Experiments were conducted under low back pressure conditions using two combustion chambers having, in both cases, an internal diameter of 17.5 mm, a curvature of radius of 38.1 mm, and an outlet angle of 90 deg, with gaseous C2H4 and O2 as the propellants. One was made of SUS and the other of resin. In addition to vibrations and bottom center pressure, pressure distribution on the sidewalls was measured for the SUS combustor, and high-speed camera observations of self-luminescence from the radial direction were conducted for the resin combustor. These measurements were compared by varying the equivalence ratio. The frequency analysis results obtained from vibrations and self-luminescence indicated that the strongly-coupled detonation mode exhibited a higher peak frequency, suggesting that the detonation waves may have different propagation speeds or rotational positions. In terms of pressure distribution and self-luminescence, only the strongly-coupled detonation mode inside near the bottom surface exhibited high pressure and brightness values. This suggested the potential for converging pressure by employing rotating detonation waves and a curved tube.

The Effect of Biomechanics Information on Driver Swing Learning of Intermediate Golfers

PURPOSE This study investigates the effectiveness of biomechanics information on intermediate golfers driver swing learning. It analyzes changes in center of pressure (COP) patterns, GRF Direction Inclination, driver performance, and learners psychological responses to determine the learning effects.METHODS Subjects were 32 right-handed male golfers (handicap 15-23) who had no difficulty in performing the golf driver swing (Full swing). Four groups were selected, BF (Biomechanics Feedback group), BVC (Biomechanics Verbal Cue group), CB (Combination group), and CT (Control group), and assigned randomly. Driver swing learning showed results after 6 weeks,and a transfer test was conducted 1 week after the completion of the learning.RESULTS Analysis of COP patterns and GRF Direction Inclination indicated changes in the BF, BVC, and CB groups. Furthermore, analysis of driver distance (m), club head speed (km/h), and ball spin rate (rpm) revealed that during the 6-week acquisition phase, all three groups (excluding the control group) showed improvements in driver distance, club head speed, and ball spin rate. However, there were no statistically significant differences among the groups. In contrast, the transfer test showed statistically significant differences among the groups, with the CB group exhibiting the highest driver distance. Learners' psychological responses during the learning process were trust, understanding, and satisfaction. The understanding factor was relatively higher in the CB and BVC groups compared to the BF group.CONCLUSIONS In summary, biomechanics information (BI) was effective in improving driver performance, and changesappeared in the COP pattern and GRF Direction Inclination, indicating a change in movement. Therefore, BI can be fully utilized for athletes or high-level advanced players and for motor learning for intermediate-level students.However, BI can only improve learning effects by strengthening learners' “understanding” when visual feedback forms and verbal cues are provided together.

Acute effects of static and dynamic stretching for ankle plantar flexors on postural control during the single-leg standing task

ABSTRACT Static stretching (SS) and dynamic stretching (DS) are widely used as warm-ups before sports. However, whether stretching affects postural control remains unclear. We compared the effects of SS and DS on the plantar flexors and postural control during single-leg standing. Fifteen healthy young participants performed SS, DS, or no stretching (control). The stretch condition consisted of four sets lasting 30 s each. The control condition was a rest with standing for 210 s. Center of pressure (COP) displacement was measured using a force plate before and after each intervention to assess postural control during the single-leg standing task. The COP area, COP velocity, and anteroposterior (COPAP) and mediolateral (COPML) range were calculated. DS significantly decreased in the COPML range (21.5 ± 4.1 to 19.0 ± 2.5 mm; P = 0.02), COP velocity (33.8 ± 7.6 to 29.8 ± 6.5 mm/s; P < 0.01), and COP area (498.6 ± 148.3 to 393.3 ± 101.1 mm2; P < 0.01), whereas SS did not change in the COP parameters (COP area 457.2 ± 108.3 to 477.8 ± 106.1 mm2, P = .49; COP velocity 31.2 ± 4.2 to 30.7 ± 5.8 mm/s, P = 0.60; COPAP 25.4 ± 3.1 to 25.3 ± 3.2 mm, P = 0.02; COPML 20.7 ± 3.3 to 21.1 ± 2.5 mm, P = 0.94). Therefore, DS of the plantar flexors enhances postural control during single-leg standing and may be effective for both injury prevention and performance enhancement.