Search Results (39)

Objective: Volleyball athletes require well-developed balance control during spiking, blocking, rapid movement, and landing. Joint range of motion (ROM) may also influence limb extension, support adjustment, and center-of-mass control. Previous studies have usually examined balance ability and joint ROM as separate factors related to volleyball performance. However, the associations between dynamic balance, static balance, and multi-joint ROM in the upper and lower limbs remain insufficiently understood. This study therefore aimed to examine the relationship between balance performance and upper- and lower-limb joint ROM in female college volleyball athletes. Methods: Thirty-five female college volleyball athletes were included. Dynamic balance of the upper and lower limbs was assessed using the Y-Balance Test, and static balance was evaluated under eyes-open and eyes-closed conditions using a static balance platform. Upper- and lower-limb ROM was measured using an electronic goniometer and the knee-to-wall test. Paired-sample t-tests were used to compare bilateral differences and differences between visual conditions. Pearson correlation analysis was performed to examine associations between joint ROM and balance performance, and false discovery rate (FDR) correction was applied to account for multiple comparisons. Results: (1) No significant bilateral difference was observed in upper-limb YBT-UQ performance (p > 0.05); for lower-limb YBT-LQ performance, a significant difference was found only in the anterior direction, with the right side showing higher values than the left side (p < 0.01). (2) Static balance parameters under the eyes-closed condition were significantly poorer than those under the eyes-open condition (p < 0.01); under the same visual condition, only the total sway path length of the right foot was significantly shorter than that of the left foot (p < 0.05). (3) The ranges of motion of right shoulder flexion, shoulder horizontal adduction, shoulder external rotation, elbow flexion, and knee-to-wall distance were significantly greater than that of the left side (all p < 0.05), and right hip internal rotation ROM was also significantly greater than that of the left side (p < 0.01). (4) Dynamic balance was correlated with selected joint ROM measures. Specifically, the anterior reach direction of the right YBT-LQ was positively correlated with hip flexion ROM (r = 0.593, p < 0.01) and knee-to-wall distance (r = 0.653, p < 0.01), and these correlations remained statistically significant after FDR correction. (5) Static balance parameters were correlated with selected lower-limb joint ROM measures in the original correlation analysis; however, these correlations did not remain significant after FDR correction. Conclusions: Female college volleyball athletes demonstrated a certain degree of bilateral asymmetry in dynamic balance and a pronounced dependence on visual input during static balance tasks. After FDR correction, the associations between the anterior reach direction of the right YBT-LQ and both hip flexion ROM and knee-to-wall distance remained stable, suggesting that these ROM measures may be related to anterior dynamic balance performance. These findings may provide a reference for postural control assessment and the development of sport-specific training programs for female volleyball athletes. Full article

Accurate assessment of postural sway is essential for evaluating balance disorders, rehabilitation outcomes, and fall risk. Traditional laboratory-based motion capture systems provide precise center-of-pressure (CoP) measurements, but are expensive, non-portable, and impractical for widespread clinical use. This study describes the development and testing (reliability and validity) of a portable three-dimensional (3D) camera system (Intel RealSense D415) for quantifying sway and balance. Test–retest reliability was evaluated in healthy adults (n = 10; 6 males, 4 females; mean age 22.3 ± 1.6 years), yielding intraclass correlation coefficients ICC = 0.84–0.86 (95% CI: 0.61–0.95). Concurrent validity, established against a laboratory-based optical motion capture system (Optotrak), demonstrated strong correlations with a mean absolute percentage error of 10.5% relative to Optotrak-derived path length measurements and high levels of agreement. Operating at 30 Hz with end-to-end latency of <40 ms, the RealSense-based system provides a reliable, valid, and portable alternative to lab-based systems. Low-cost markerless motion capture systems based on standard RGB cameras have been validated for postural risk assessment, showing good consistency with gold-standard Vicon systems. These preliminary findings suggest that the system shows promise as a low-cost alternative; however, further validation in clinical populations is required before clinical deployment. Full article

Background/Objective: In late adulthood, the increasing prevalence of diabetes overlaps with the highest prevalence of postural instability. A cross-sectional study was designed to explore the combined influence of age, gender, history of COVID-19 quadriceps strength, and Body Mass Index (B.M.I.) on the postural stability of adults with/without diabetes, under a variety of sensory conditions. Methods: A total of 263 adults aged 21 to 82 years old accepted to participate, 99 with and 164 without diabetes. They had no history of vestibular/otology/neurology/autoimmune/orthopedic disease or proliferative retinopathy/severe renal dysfunction/traumatic injury. After clinical and vestibular evaluations, postural sway was recorded on hard/soft surface, eyes open/closed, and without/with 30° neck extension. Bivariate analysis and repeated measures multivariate analysis of covariance were performed with 0.05 significance. Results: In the two groups, two thirds of the participants had excess weight and almost half had history of COVID-19. Overall conditions, gender and diabetes were the main factors contributing to sway area (multiple R = 0.28–0.31, p ≤ 0.001) and to sway length (multiple R = 0.34–0.47, p ≤ 0.00001). Compared to adults without diabetes, in those with diabetes, the age was not related to sway measurements; with contribution to sway from history of COVID-19 and quadriceps strength, and decreased contribution of the study variables to both the anterior–posterior position of the center of pressure and ankle movement (velocity as a function of the anterior–posterior position of the center of pressure) (p > 0.05). Conclusions: Diabetes may interfere with the influence of individual cofactors contributing to postural sway, including decreased influence of age and reduced ankle movement. A history of mild–moderate COVID-19 may have influence on postural control in varied sensory conditions. Full article

Postural sway derived from center-of-pressure (CoP) trajectories is widely used to assess balance and fall risk in older adults, but conventional linear metrics mainly quantify sway magnitude and may overlook temporal organization. Guided by the loss-of-complexity hypothesis, we re-examined associations between fall history and linear and non-linear CoP metrics in an open-access dataset. Quiet-standing trials under eyes-open and eyes-closed conditions were analyzed in adults ≥60 years (fallers n = 19; non-fallers n = 57). To reduce confounding, propensity score matching was performed using age, sex, body mass index, activities of daily living level, illness status, number of medications, disability status, and orthosis/prosthesis use. Linear and non-linear indices, including recurrence quantification analysis, detrended fluctuation analysis, fractal dimension, multiscale entropy, stabilogram diffusion analysis, and sway density measures, were examined. After matching, no CoP metric differed significantly between groups. However, SHAP-based exploratory analysis suggested that non-linear features related to temporal structure and multiscale organization contributed more prominently to model output than conventional magnitude-based metrics. Given the limited sample size, these findings should be interpreted as exploratory and hypothesis-generating. Full article

Postural control relies on the integration of visual, vestibular, and somatosensory inputs under biomechanical constraints. Conventional Romberg testing provides limited quantitative insight, particularly regarding directional control and sensory dependence. Wearable inertial measurement units (IMUs) enable portable, multidimensional assessment of postural sway. Thirty healthy adults (15 females, 15 males) completed a modified Romberg protocol with systematic manipulation of stance (normal, tandem), visual condition (eyes open, eyes closed), and arm position (arms at sides, arms forward), including both left and right leading foot during tandem stance. Whole-body kinematics were recorded using a full-body IMU system comprising 17 wireless sensors. Center-of-mass (CoM) trajectories were derived from a 23-segment biomechanical model, and linear, spatial, and nonlinear sway metrics were computed. Statistical analyses were conducted using repeated-measures ANOVA, with significance set at p < 0.05. Visual deprivation significantly increased sway path length, mean sway velocity, and sway area across all stance conditions (p < 0.001). Tandem stance elicited greater mediolateral sway than normal stance (p < 0.001). Romberg ratios exceeded unity for all metrics and were significantly higher in tandem stance (p < 0.01). Arm position effects were negligible in normal stance but showed significant Vision × Arm interactions during tandem stance (p < 0.05). Leading foot position had no significant main effects. Combining a modified Romberg protocol with full-body IMU-based CoM analysis enables sensitive characterization of sensory dependence and directional postural control. Tandem stance with visual deprivation increases mediolateral postural demands under reduced base-of-support conditions, providing a more challenging context for evaluating directional postural control. Full article

Enhancement of postural stability in standing is essential for fall prevention in the context of demographic aging. Against such a background, this study proposes a personalized training system based on individual limits of stability (LOS) for a human standing state. The system evaluates LOS in eight directions using center-of-mass (COM) and center-of-pressure (COP) measurement devices and provides game-based feedback, then promotes balance within the relevant LOS parameters. Loading is individualized by applying greater force to virtual objects as the COP approaches the LOS determined for each subject. Experiments with 32 younger and 19 mature subjects produced evaluations for postural stability index (IPS), LOS area, and COP sway. The results revealed two distinct response patterns: LOS expansion and sway reduction, both observed across younger and mature cohorts. These findings suggest that individualized LOS-based training can be applied to improve standing stability with two distinct strategies. These preliminary findings suggest that individualized LOS-based training is associated with changes in standing stability through two distinct response patterns. Full article

Background/Objectives: Beyond the core characteristics of the condition, autistic individuals often significantly struggle with postural balance. This pilot study aimed to investigate the effects of an immersive virtual reality-based training administered with Gait Real-time Analysis Interactive Lab (GRAIL) on postural balance of autistic children. Methods: A total of 20 autistic participants aged 6 to 13 were enrolled in a 5-week randomized, parallel-group, open-label, controlled trial, and received either balance training with the GRAIL system or no training. The trial was registered at ClinicalTrials.gov (identifier: NCT04276571). The primary outcome measures were the change in center of pressure (CoP) metrics during GRAIL balance assessments and the change in motor skills as assessed with Movement Assessment Battery for Children-2. Secondary outcome measures included parent-report Developmental Coordination Disorder Questionnaire, center of mass metrics, and gait parameters evaluated with GRAIL. ANCOVA tests were performed for all outcomes, with time (T0 and T1) as within-subjects factor, the group (training and control groups) as between-subjects factor, and considering age as covariate. Results: Slight but significant time by group interactions were found in some CoP metrics (i.e., sway path length, velocity in the antero-posterior direction, and the jerk). Conclusions: These findings preliminarily suggest that a virtual reality-based training may induce slight modifications in postural balance strategies, which can be enhanced with longer or more intensive training. Full article

This study investigated the interplay of bodily degrees of freedom (DoFs) governing the collective variable comprising the center of pressure (CoP) and center of mass (CoM) in postural control through the analytical lens of multiplicative interactions across scales. We employed a task combination involving a wobble board, introducing mechanical instability mainly along the mediolateral (ML) axis and the Trail Making Task (TMT), which imposes precise visual demands primarily along the anteroposterior (AP) axis. Using Multiscale Regression Analysis (MRA), a novel analytical method rooted in Detrended Fluctuation Analysis (DFA), we scrutinized CoP-to-CoM and CoM-to-CoP effects across multiple timescales ranging from $100\mathrm{ms}$ to $10\mathrm{s}$. CoP was computed from ground reaction forces recorded via a force plate, and CoM was derived from full-body 3D motion capture using a biomechanical model. We found that the wobble board attenuated CoM-to-CoP effects across timescales ranging from $100\mathrm{to}400\mathrm{ms}$. Further analysis revealed nuanced changes: while there was an overall reduction, this encompassed an accentuation of CoM-to-CoP effects along the AP axis and a decrease along the ML axis. Importantly, these alterations in CoP’s responses to CoM movements outweighed any nonsignificant effects attributable to the TMT. CoM exhibited no sensitivity to CoP movements, regardless of the visual and mechanical task demands. In addition to identifying the characteristic timescales associated with bodily DoFs in facilitating upright posture, our findings underscore the critical significance of directionally challenging biomechanical constraints, particularly evident in the amplification of CoP-to-CoM effects along the AP axis in response to ML instability. These results underscore the potential of wobble board training to enhance the coordinative and compensatory responses of bodily DoFs to the shifting CoM by prompting appropriate adjustments in CoP, thereby suggesting their application for reinstating healthy CoM–CoP dynamics in clinical populations with postural deficits. Full article

In the context of global population aging, identifying reliable, objective tools to assess physical function and postural stability in older adults is increasingly important to mitigate fall risk. This study presents a non-contact platform that uses a Microsoft Azure Kinect depth camera to evaluate functional performance related to lower-limb muscular capacity and static balance through self-selected depth squats and four progressively challenging stances (feet apart, feet together, semitandem, and tandem). By applying markerless motion capture algorithms, the system provides key biomechanical parameters such as center of mass displacement, knee angles, and sway trajectories. A comparison of older and younger individuals showed that the older group tended to perform shallower squats and exhibit greater mediolateral and anteroposterior sway, aligning with age-related declines in strength and postural control. Longitudinal tracking also illustrated how performance varied following a fall, indicating potential for ongoing risk assessment. Notably, in 30 s balance trials, the first 10 s often captured meaningful differences in stability, suggesting that short-duration stance tests can reliably detect early signs of imbalance. These findings highlight the feasibility of low-cost, user-friendly depth-camera technologies to complement traditional clinical measures and guide targeted fall-prevention strategies in older populations. Full article

Background: Sounds that cause disturbances and perturbations to the vestibular (inner ear organ responses) and visual (acute oculomotor responses) systems can impact postural stability. The purpose of this study was to assess the impact of different types of sounds and noises on both static and dynamic PS. Methods: A total of 20 participants (12 females and 8 males; age: 21.35 ± 1.79 years; height: 170.7 ± 9.3 cm; mass: 66.725 ± 14.1 kg) were tested using the limits of stability (LOS) test on the BTrackS™ balance plate and a Timed Up and Go (TUG) test, when exposed to four different sounds and occupational noises [construction noise (CN), white noise (WN), sirens (SRs), and nature sounds (NAs)] in a randomized order with a no sounds (NSs) control performed initially (intensity range of 70–80 dB). The center of pressure (COP) total sway area (cm²) from the LOS and the time to completion of the TUG (seconds) were analyzed using a one-way repeated measures of analysis of variance at an alpha level of 0.05. Results: The observations demonstrated significant differences between the sounds and noises for the TUG (p < 0.001) but not for the LOS test (p = 0.406). Pairwise comparisons for the significant main effect for the TUG revealed that NSs demonstrated significantly slower time to completion compared to CN, WN, and SRs but not NAs. Conclusions: The findings suggest that the different sounds and noises did not impact static PS during the LOS test, which involved the voluntary excursion of the COP while maintaining the same base of support (BOS). However, during dynamic PS with a changing BOS while walking in the TUG, exposure to CN, SRs, and WN demonstrated a faster completion time than NSs or NAs. This finding may be attributed to the anxiety induced by the noise immersion and perception of sounds, compared to calm NAs and no sounds. The findings can aid in better understanding the impact of different occupational noises on PS and emphasize the need for better noise protection and reduction in loud work environments. Full article

Balance assessment is a key metric for tracking the health and fall risk of individuals with balance impairment. Leveraging wearable sensors and mobile devices can increase clinical accessibility to objective balance metrics. Previous work has been conducted validating center of mass (COM) acceleration metrics from mobile devices against the gold standard force plate center of pressure (COP) position; however, most studies have been restricted to devices being placed close to the subject’s COM. In this study, rigid body kinematics and the inverted pendulum model were used to develop a novel methodology for calculating COM acceleration using mobile devices in arbitrary positions, as well as an approach for conversion of COM measurements to COP position for direct validation with force plate measurements. Validation of this methodology included a direct comparison of smartphone and force plate results for COM accelerations and COP positions, as well as statistical comparisons using Spearman’s rank correlation. The results show strong analysis performance for both approaches during a subject’s intentional swaying, with more limited results in cases of little motion. The strong performance warrants future work to further improve accessibility by removing dependence on motion capture systems or replacing them with cost-effective alternatives. The accurate tracking of COM acceleration and COP position information for mobile devices at arbitrary positions increases the flexibility for future mobile or at-home balance assessments. Full article

Post-activation performance enhancement (PAPE) has been proposed to improve strength, power, or speed following a conditioning contraction, yet, few studies have investigated its impact on postural performance. This study aimed to examine the effects of an acute bout of plyometric exercise with varying recovery intervals on unilateral countermovement jump (CMJ) performance and postural sway in female volleyball players. Twenty-four national-level female athletes (age: 20.83 ± 2.93 years; height: 1.72 ± 0.18 m; body mass: 61.21 ± 11.77 kg; and body mass index: 20.60 ± 2.67 kg/m²) participated in the study. They conducted unilateral CMJ and postural sway assessments on both dominant and non-dominant legs under baseline conditions, as well as four recovery intervals (2 min: R2, 4 min: R4, 6 min, R6, and 8 min: R8). These assessments were performed following a 30 s repetitive CMJ (RCMJ-30) serving as an acute plyometric conditioning activity. A force plate was used to capture force–time- and center of pressure-derived metrics. Maximum and mean jump heights during the RCMJ-30 test demonstrated moderate-to-good interday reliability (intraclass correlation coefficient = 0.62–0.83). Significant differences in unilateral CMJ and postural sway metrics were observed across conditions following the plyometric stimulus. R8 was the most effective recovery interval for improving both jump height and flight time in both legs (p < 0.01). The greatest enhancement in unilateral postural performance was found in the R6 condition (p < 0.05), with more pronounced effects in the non-dominant leg. These findings support the effectiveness of the RCMJ-30 as a PAPE protocol for enhancing both unilateral CMJ performance and postural control. Practitioners should adjust recovery intervals based on specific performance goals to maximize PAPE benefits. Full article

Objectives: Altered body biomechanics during pregnancy can lead to balance impairments and an increased risk of falls. Clinical exercise interventions can help regulate these biomechanical changes. Methods: A total of 101 pregnant participants (exercise group: n = 50; control group: n = 51) were retrospectively analyzed over an 8-week follow-up period. Single-leg balance parameters, including AP sway, ML sway, total body sway, OSD, and center of pressure velocity and acceleration, were assessed considering limb dominance. Measurements were taken at baseline and week 8. Repeated-measures ANOVA was used to analyze time–group interactions, with significance set at p < 0.001. The biomechanical impacts of participant height and body mass on center of pressure dynamics were also considered. Results: The exercise group (EG) demonstrated significant improvements in all balance parameters compared to the control group (CG) (p < 0.001), except for non-dominant anterior-posterior (AP) sway (p = 0.512). In the EG, medio-lateral (ML) and AP sway of the non-dominant limb were minimized, whereas these parameters were significantly increased in the CG. Although both groups exhibited an increased one-leg stance duration (OSD), the improvement was more pronounced in the EG. The controlled improvements observed in the EG suggest a protective effect of exercise on balance, particularly in the dominant limb. Conclusions: Clinical exercise interventions during pregnancy enhance balance parameters, reduce fall risk, and improve functional mobility. These findings suggest that structured exercise programs not only support maternal well-being but also improve reactive balance control. Given the biomechanical changes throughout pregnancy, future studies should examine the center of pressure velocity, acceleration, and the influence of maternal anthropometrics on postural stability to refine exercise recommendations. Full article

Background: Falls and fall consequences in older adults are global health issues. Previous studies have compared postural sways or stepping strategies between older adults with and without fall histories to identify factors associated with falls. However, more in-depth neuromuscular/kinematic mechanisms have remained unclear. This study aimed to comprehensively investigate muscle activities and joint kinematics during reactive balance control in older adults with different fall histories. Methods: This pilot observational study recruited six community-dwelling older fallers (≥1 fall in past one year) and six older non-fallers, who received unpredictable translational balance perturbations in randomized directions and intensities during standing. The whole-body center-of-mass (COM) displacements, eight dominant-leg joint motions and muscle electrical activities were collected, and analyzed using the temporal and amplitude parameters. Results: Compared to non-fallers, fallers had significantly: (a) smaller activation rate of the ankle dorsiflexor, delayed activation of the hip flexor/extensor, larger activation rate of the knee flexor, and smaller agonist-antagonist co-contraction in lower-limb muscles; (b) larger knee/hip flexion angles, longer ankle dorsiflexion duration, and delayed timing of recovery in joint motions; and (c) earlier downward COM displacements and larger anteroposterior overshooting COM displacements following unpredictable perturbations (p < 0.05). Conclusions: Compared to non-fallers, fallers used more suspensory strategies for reactive standing balance, which compensated for inadequate ankle/hip strategies but resulted in prolonged recovery. A further longitudinal study with a larger sample is still needed to examine the diagnostic accuracies and training values of these identified neuromuscular/kinematic factors in differentiating fall risks and preventing future falls of older people, respectively. Full article

Background/Objectives: Long-term work-related musculoskeletal disorders are predominantly influenced by factors such as the duration, intensity, and repetitive nature of load lifting. Although traditional ergonomic assessment tools can be effective, they are often challenging and complex to apply due to the absence of a streamlined, standardized framework. Recently, integrating wearable sensors with artificial intelligence has emerged as a promising approach to effectively monitor and mitigate biomechanical risks. This study aimed to evaluate the potential of machine learning models, trained on postural sway metrics derived from an inertial measurement unit (IMU) placed at the lumbar region, to classify risk levels associated with load lifting based on the Revised NIOSH Lifting Equation. Methods: To compute postural sway parameters, the IMU captured acceleration data in both anteroposterior and mediolateral directions, aligning closely with the body’s center of mass. Eight participants undertook two scenarios, each involving twenty consecutive lifting tasks. Eight machine learning classifiers were tested utilizing two validation strategies, with the Gradient Boost Tree algorithm achieving the highest accuracy and an Area under the ROC Curve of 91.2% and 94.5%, respectively. Additionally, feature importance analysis was conducted to identify the most influential sway parameters and directions. Results: The results indicate that the combination of sway metrics and the Gradient Boost model offers a feasible approach for predicting biomechanical risks in load lifting. Conclusions: Further studies with a broader participant pool and varied lifting conditions could enhance the applicability of this method in occupational ergonomics. Full article