Motor Control最新文献

Artificially restricting the center of mass (COM) motion during quiet standing through multisegment constraints has previously been shown to alter center of pressure (COP) dynamics. Increases in COP motion during such mechanically restricted stances have been interpreted as potential markers of exploratory behavior, whereby the central nervous system may generate movements to gather sensory input that would otherwise be limited by the imposed constraints. However, past studies relied on a plank-based apparatus that places participants in a nonecological posture, potentially limiting interpretations. This study compared the effects of the plank-based setup and a more ecologically valid belt-based apparatus that restricts COM movement without fully constraining the body. The analysis focused on both traditional measures of COP (i.e., variability) and dynamic measures (i.e., regularity and frequency components). Participants performed standing trials with both apparatuses, with eyes open and closed. Results revealed distinct COP behaviors between the two systems: compared with the unrestricted condition, the restricted condition with the plank-based apparatus yielded higher COP variability and regularity, whereas the belt-based system yielded lower COP variability and increased irregularity. These effects were not strongly influenced by visual input. The persistent COP motion observed under both conditions suggests that COP displacement may serve functions beyond merely stabilizing the COM, possibly reflecting exploratory behaviors. Overall, our findings support the use of belt-based systems as a more ecological alternative for restricting the COM motion, allowing for the study of the role of the COP in sensorimotor regulation without the limitations of a multisegment constraint.

The objective of this study is to examine the relationship between the spin-related variables during real four-seam fastball pitching in baseball and the finger force production capability and its coordination in the laboratory test. Consequently, the sets of variables were derived from two distinct experiments: a field task and a laboratory task. The field task was designed to quantify the spin-related variables during actual pitching performance, and the laboratory task was designed to quantify the strength of the two fingers and the coordination-related variables of the index and middle fingers during the cyclic net finger force production task. The statistical test was implemented with the primary objective of ascertaining the significant correlation between the two metrics from the field and laboratory tests. The findings indicated a negative correlation between finger forces and spin-related variables (p < .05), suggesting that those who have greater finger force do not have a positive effect on spin-related variables. The strength of the synergy indices of moment stabilization was associated with a positive effect on spin-related variables (p < .05). The present experiment demonstrated that the stabilization of mechanical variables by the force production of the two fingers, that is, the net moment, indicates that the rotational effect of finger force production plays a critical role in determining the superior spin qualities of a fastball pitch in baseball.

Background: Prolonged standing demands continuous postural adjustments to redistribute weight and maintain comfort. People with Parkinson's disease (PwPD) may show impaired adaptability due to motor symptoms and rigidity. The effects of dopaminergic medication on postural control during prolonged standing are not well understood. This study aims to analyze the impact of dopaminergic medication on postural control during prolonged standing in PwPD, focusing on both global sway characteristics and discrete postural adjustments.

Methods: Twenty-two PwPD (Hoehn and Yahr II-III) performed a 15-min standing task on a force plate in randomized ON (medicated) and OFF (unmedicated) sessions. Global sway parameters (sway area, root mean square, velocity, and frequency) and discrete postural adjustments (shifts, fidgets, and drifts) were calculated from center of pressure data. Nonparametric and parametric tests compared ON and OFF states.

Results: In the ON state, participants showed significantly larger sway area, increased root mean square and velocity in anterior-posterior and mediolateral directions, and higher sway frequency (all p < .05). The number and amplitude of discrete adjustments were greater in the ON state, especially anterior-posterior drifts and mediolateral shifts. These changes indicate enhanced postural dynamics under dopaminergic medication.

Conclusion: Dopaminergic therapy promotes a more dynamic and adaptable postural control strategy during prolonged standing in PwPD. Rather than reflecting instability, increased sway and frequent adjustments suggest adaptive behaviors facilitating comfort and stability over time. These findings underscore the value of prolonged standing tasks for assessing postural control and guiding rehabilitation strategies in PwPD beyond what short static tests capture.

Background: Age-related decline can impair older adults' ability to perform tasks involving a mix of motor and cognitive goals in a dual-task (DT) paradigm. The amount of DT interference effects has typically been associated with the availability of attentional resources and the degree of balance automaticity. Older adults with mild cognitive impairment may lack sufficient sensorimotor capacity for "automatic" regulation of posture under demanding balance conditions, resulting in larger DT interference effects due to increasing attentional control.

Research question: Does the degree of automaticity affect balance stability in older adults with mild cognitive impairment during dual tasking, and does this relationship vary with the difficulty of the balance task?

Methods: Sixty-seven older adults, aged 60-80 years (23 mild cognitive impairmentss), were positioned barefoot on a single piezoelectric force plate in a double-support and tandem stance with eyes open. Each stance condition was tested as single task during performance of a mathematical counting task (i.e., DT). DT cost (DTC) scores of center-of-pressure sway velocity (DTCVcop) were calculated, and regression analyses were conducted to assess the unique contribution of baseline center-of-pressure sway entropy under single-task conditions to DTCVcop, with age, Montreal Cognitive Assessment scores, gender, and cognitive status included as covariates.

Results: Baseline sway entropy accounted for only 0.25%-4% of the variance in DTC of Vcop. Gender and cognitive status accounted for 12%-20% of the variance under double-support but not in tandem stance.

Significance: Our findings suggest that sway entropy has only minimal impact on DT interference while gender and cognitive status play a more substantial role, highlighting the importance of these factors in balance control of older adults.

Background: The great toe contributes to healthy gait and balance but may be impacted by exposure to cold. The purpose of this study was to examine the effects of 60 min of cold-water immersion on great toe flexor force and single-limb balance.

Methods: Forty-four healthy adults participated in one of two experiments. All participants placed one foot in water that was maintained at 10 °C and the other foot in water maintained at body temperature (37 °C) for 60 min. Both feet were submerged to a depth just above the malleolus. For the first experiment (n = 25), maximum voluntary great toe flexion force and control of submaximal force were measured while standing using a custom designed apparatus both before and immediately following immersion. For the second experiment (n = 19), postural sway was assessed before and after immersion while standing on an unstable surface with a single limb and eyes open.

Results: Cold-water immersion resulted in a significant decrease in maximal flexor force of the great toe (332.6 ± 111.5 N vs. 235.1 ± 108.2 N, p < .001, Cohen's d = -0.89), but it did not impact the amount of error measured during control of submaximal flexor force (13.5 ± 4.4 N vs. 14.4 ± 5.6 N, p = .368). Further, exposure to cold resulted in significant increases to center of pressure rambling in the mediolateral direction (4.0 ± 0.9 mm vs. 4.8 ± 1.0 mm, p < .001, Cohen's d = 0.79) and trembling (3.2 ± 0.9 mm vs. 3.9 ± 1.4 mm, p = .002, Cohen's d = -0.63) and range of motion (49.6 ± 15.3 mm vs. 61.8 ± 21.9 mm, p = .007, Cohen's d = -0.62) in the anteroposterior direction.

Conclusion: Cold-water immersion can impact force at the great toe and may adversely affect balance.

Fatigue experienced by individuals with multiple sclerosis (MS) during activities of daily living affects their balance and increases the risk of falls. The aim was to assess the effect of fatigue induced by a functional task on balance control in individuals with MS. The study involved 10 individuals with MS and 10 gender-matched healthy volunteers who performed a functional sit-to-stand task using a standardized chair and metronome until they reported an inability to continue. Motor Control and Sensory Organization tests were implemented using Dynamic Posturography three times: before, immediately after fatigue, and after a 30-min rest period. The Motor Control Test revealed that individuals with MS, compared to healthy controls, showed significantly longer latencies during small, medium, and large amplitudes of backward perturbation. Longer latencies were observed in the MS group after fatigue, specifically during small and large amplitudes of forward perturbations. The Sensory Organization Test discovered that following fatigue, the MS group demonstrated significantly lower equilibrium scores compared with healthy controls in the following conditions: eyes closed (p < .001), sway-referenced visual surround (p = .02), and sway-referenced support surface (p = .03). Functional fatigue induced by sit-to-stand tasks significantly impacted outcomes of both the Motor Control and Sensory Organization tests of balance control in individuals with MS. These findings lay the groundwork for future investigations into the role of fatigue in balance control in individuals with MS.

Despite the main clinical criteria for Autism Spectrum Disorder (ASD) diagnosis being the dysfunction of socio-communicative interaction abilities and the presence of restricted interests and repetitive behaviors, sensory-motor dysfunctions are also frequently observed in this population. Moreover, among sensory-motor issues, both postural control and visual processing may be impaired. The main aim of this scoping review is to synthesize the evidence on the relationship between visual behavior and postural control dysfunctions in children and adolescents with ASD. This scoping review was conducted using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocol, Extension for Scoping Reviews guidelines, and was registered a priori on the Open Science Framework. PubMed, CINAHL, Embase, PsycINFO, Scopus, and Web of Science databases were consulted. Primary studies with any study design were included. No time, geographical, or study setting limitations or language restrictions were applied. A total of 646 articles were found in the initial search, but only 14 studies met the full inclusion criteria. Findings highlighted that studies on the relationship between vision and posture in ASD children and adolescents are scarce, and their results are contrasting because of the significant heterogeneity in the methods. This scoping review carried out a relevant survey of the literature considering the relationship between vision and posture in ASD. Nonetheless, the characteristics of the included sample and the methodology used in the analyzed studies were highly variable. Thus, rigorous study methods with population-specific objective outcome measures are needed to draw generalizable conclusions.

Anterior cruciate ligament reconstruction (ACLR) can result in persistent deficits in postural stability particularly under dual-task conditions involving cognitive demands. This study investigated the effects of cognitive tasks from different domains on postural control among individuals with ACLR compared with healthy controls. Twenty-five individuals with ACLR and 25 asymptomatic matched controls performed three cognitive tasks of backward counting (working memory), Stroop Color-Word Test (executive function), and Benton's Judgment of Line Orientation (visuospatial perception) under single- (seated) and dual-task (single-leg stance on rigid and foam surfaces) conditions. Postural stability was quantified by measuring center-of-pressure sway area and sway velocity in anterior-posterior and medial-lateral directions. Cognitive performance was evaluated by counting task errors. Results indicated significantly greater postural sway in the ACLR group compared with controls across all tasks (p < .01), with the Stroop Color-Word Test significantly increasing mean sway velocity compared with the no-task condition (p < .01) in only the ACLR group. ACLR participants also demonstrated consistently greater cognitive errors under all conditions. However, cognitive errors were not significantly affected by increased postural difficulty. Findings suggest that executive function tasks uniquely exacerbate postural control deficits following ACLR, highlighting the clinical importance of incorporating targeted cognitive-postural training focusing on executive control into rehabilitation protocols.

Different attentional focus strategies are commonly employed in sports training, with the external focus of attention (EF) strategy shown to enhance performance in the standing long jump. However, the underlying muscular dynamics responsible for this improvement remain unclear. In this study, we utilized a Latin square design to recruit 12 healthy male participants, each undergoing standing long jump testing under EF, internal focus (IF), and control conditions. During the take-off phase, we synchronously recorded kinematic and dynamic data. Inverse dynamics calculations were performed on the dynamic and kinematic data. Compared with IF and control, the EF condition exhibited longer jump distances, lower projection angles, and higher peak horizontal take-off velocities and impulses alongside increased center of mass displacement during the eccentric phase and decreased center of mass displacement during the concentric phase (p < .05). The peak muscle force and rate of muscle force development of the vastus lateralis, vastus medialis, vastus intermedius, and gluteus maximus during the take-off phase were also higher in the EF group (p < .05). These results indicate that the EF strategy optimizes standing long jump mechanics by enhancing the efficiency of eccentric muscle contractions, thereby increasing stored elastic potential energy in the muscles. Consequently, this leads to greater muscle force and rate of muscle force development during the concentric phase, ultimately resulting in increased jump distances.

Introduction: Chronic ankle instability (CAI) is a common sequela of lateral ankle sprains that impairs postural stability during functional tasks. External biofeedback may be an appropriate rehabilitation tool to improve functional movement; however, more research is needed to determine its effectiveness in dynamic tasks in individuals with CAI. This study aimed to assess the effect of real-time external biofeedback via laser on dynamic postural stability indices during a single-limb forward hop-to-stabilization task in participants with CAI.

Methods: Eighteen participants with CAI completed five successful forward hop-to-stabilization jumps with and without external biofeedback using a single-dot laser attached to the distal tibia. A single inertial measurement unit fastened to the lower back captured dynamic postural stability indices in the vertical, anterior-posterior, medial-lateral, and the resultant of each plane during the 5 s after landing. The mean difference between biofeedback and no biofeedback was assessed using independent t tests.

Results: Our results indicate no significant differences were observed between forward hop-to-stabilization tasks with and without real-time external biofeedback in individuals with CAI.

Discussion: More research is needed to determine the appropriate biofeedback tool location and modality type of external biofeedback in addition to the minimum amount of training exposure to improve dynamic postural stability during a single-limb landing task.