Sway Length Research Articles

Roles of Size, Position, and Speed of Stimulus in Vection with Stimuli Projected on a Ground Surface.

Although the induction of vection (perception of illusory self-motion) has been studied for some decades, the effect of ground surface properties on vection remains to be assessed quantitatively. This study will be helpful for designing helicopter or airplane flight simulation, because pilots often perceive optic flow on the ground surface and perceive self-motion from such flows. Vection stimuli of variable position, size, and optic flow speed were presented in a trapezoidal area on a ground surface. Body sway was also measured. Substantial vection was induced by stimuli on a ground surface. Increases in stimulus speed and size were each associated with stronger vection (e.g., the subjective strength increased by 50% as the speed increased from 0.375 m·s(-1) to 1.5 m·s(-1)). When the stimulus occupied a more distant section of the visual field, vection was more efficiently induced than when the nearer section was occupied (e.g., the subjective strength decreased by 50% when the nearer half section of optical flow was removed). These properties of vection were similar to vection induced by upright vertical stimuli. Speed, size, and position of vection stimuli modified both length and direction of body sway significantly. Vection and body sway showed some correlations (e.g., r=0.55). Stimuli on ground surfaces can induce substantial vection and vection strength can be modified by the stimulus properties of the ground surfaces.

Girls with generalized joint hypermobility display changed muscle activity and postural sway during static balance tasks

Objectives: To study knee muscle activity and static postural sway in girls with generalized joint hypermobility (GJH).Method: Sixteen girls with GJH and 11 girls with non-GJH (NGJH) aged 14 years, randomly recruited among schoolchildren, participated in this study. GJH inclusion criteria were: Beighton score minimum 6/9 and one hypermobile knee; for NGJH: Beighton score maximum 5/9 and no knees with hypermobility. The participants performed a static two-legged balance test with eyes open (2EO) and eyes closed (2EC) and a one-legged stance test with eyes open (1EO). Postural sway (centre of pressure path length, COPL) was calculated, along with rambling and trembling components. Surface electromyography (sEMG) from the quadriceps (Q), hamstrings (H), and gastrocnemius (G) muscles was recorded, expressed as a percentage of the maximum voluntary EMG (%MVE), and the co-contraction index (CCI) of Q, H, and G muscle activity was calculated. Knee function was self-reported using the Knee Injury and Osteoarthritis Outcome Score for children (KOOS-Child).Results: GJH had a significantly lower lateral HQ CCI and a higher medial/lateral HQ CCI ratio in all balance tasks. Group mean EMG varied from 1.3%MVE in Q (during 2EO) to 15.7%MVE in G (during 1EO). GJH had larger postural sway length than NGJH during 2EC (COPL 1.64 vs. 1.37 m/min, p < 0.001). Rambling and trembling components did not differ between groups.Conclusions: Girls with GJH and at least one hypermobile knee performed, compared with NGJH, static balance tasks with higher medial knee muscle activity relative to the lateral activity, and larger postural sway when vision was eliminated. The short- and long-term consequences should be studied further.

Effects of modified sit-to-stand training on balance control in hemiplegic stroke patients: a randomized controlled trial

Objective: To explore the effectiveness of modified sit-to-stand training on balance function in hemiplegic stroke patients. Design: Randomized controlled trial. Setting: Rehabilitation medical centre. Participants: A total of 50 hemiplegic patients with stroke were randomly assigned to the control and experimental groups (n = 25 for each group). Interventions: Patients in the control group received the sit-to-stand training with symmetrical foot position, while patients in the experimental group were given the modified sit-to-stand training in which the paretic foot placed posterior. Subjects in both groups received 30 minutes of sit-to-stand training, five times a week, for four weeks. Main outcome measures: The time and weight-bearing distribution during sit-to-stand movement, the centre of pressure sway length during quiet standing, the centre of pressure sway areas during dynamic standing and Berg Balance Scale were assessed before and after completing the four-week sit-to-stand training. Results: Our data showed significant improvements in standing balance and the sit-to-stand movement for two groups in the post-training compared with the pre-training. After training, the rise time shortened more significantly in the experimental group (mean change, 0.90 ±0.25 seconds) than the control group (mean change, 0.42 ±0.18 seconds). Weight-bearing asymmetry showed significantly greater improvement in the experimental group (mean change, 0.17 ±0.10) than in the control group (mean change, 0.06 ±0.05). Centre of pressure sway length was significantly smaller in the experimental group (mean change, 27.85 ±10.58 cm) than in the control group (mean change, 21.95 ±8.19 cm). Centre of pressure sway areas was significantly larger in the experimental group (mean change, 84.24 ±26.48 cm2) than in the control group (mean change, 67.74 ±22.84 cm2) (P = 0.027). The Berg Balance Scale was significantly higher in the experiment group (mean change, 8.4 ±3.1) than the control group (mean change, 5.8±2.8). Conclusions: A modified sit-to-stand training improves the balance function in hemiplegic stroke patients.

Association between attentional function and postural instability in Japanese older patients with diabetes mellitus.

This study assessed the association between attentional function and postural instability in older Japanese patients with diabetes. This cross-sectional study included 168 older patients with diabetes who were referred to an outpatient diabetic clinic between June and July 2013. The Trail Making Test-A (TMT-A) was used to evaluate attentional function. Posturography was used to evaluate postural sway. Indices of postural sway were the total length and the enveloped area. Analysis of covariance was used to estimate the multivariable-adjusted means of indices of postural sway according to tertile of TMT-A. After adjustment for age, sex, regular exercise, diabetic retinopathy, bilateral numbness and/or paresthesia in the feet, hemoglobin A1c level, quadriceps strength, and Mini-Mental State Examination score, patients with lower attentional function had higher postural sway length (tertile 3 vs. tertile 1, p=0.010) and enveloped area (tertile 3 vs. tertile 1, p=0.030) levels than those with higher attentional function. Among older patients with diabetes who did not have dementia, patients with lower attentional function may have more postural instability than those with higher attentional function.

Pain education combined with neck- and aerobic training is more effective at relieving chronic neck pain than pain education alone – A preliminary randomized controlled trial

ObjectiveTo evaluate the effect of training and pain education vs pain education alone, on neck pain, neck muscle activity and postural sway in patients with chronic neck pain. MethodsTwenty women with chronic neck pain were randomized to receive pain education and specific training (neck–shoulder exercises, balance and aerobic training) (INV), or pain education alone (CTRL). Effect on neck pain, function and Global Perceived Effect (GPE) were measured. Surface electromyography (EMG) was recorded from neck flexor and extensor muscles during performance of the Cranio-Cervical Flexion Test (CCFT) and three postural control tests (two-legged: eyes open and closed, one-legged: eyes open). Sway parameters were calculated. ResultsFifteen participants (CTRL: eight; INV: seven) completed the study. Per protocol analyses showed a larger pain reduction (p = 0.002) for the INV group with tendencies for increased GPE (p = 0.06), reduced sternocleidomastoid activity during the CCFT (p = 0.09), reduced sway length (p = 0.09), and increased neck extensor activity (p = 0.02) during sway compared to the CTRL group. ConclusionPain education and specific training reduce neck pain more than pain education alone in patients with chronic neck pain. These results provide encouragement for a larger clinical trial to corroborate these observations.

Effects of therapeutic Tai Chi on balance, gait, and quality of life in chronic stroke patients.

The aim of this study was to analyze the effects of therapeutic Tai Chi on balance, gait, and quality of life in chronic stroke patients. Twenty-two inpatients diagnosed with stroke were divided randomly into two groups: one treated with both general physical therapy and Tai Chi exercise (11 patients) and one treated with only general physical therapy (11 patients). Therapeutic Tai Chi included 10 different movements and was performed for 60 min, twice per week, for 6 weeks. Pretest and post-test measurements were recorded for sway length and sway velocity using Gaitview, the functional reach test, the dynamic gait index, the 10-m walking test, the timed up-and-go test, and SF-36 survey. Both the Tai Chi group and the control group showed a significant improvement in sway length and sway velocity, and the Tai Chi group showed greater improvement than the control group in degree of variation. In addition, only the Tai Chi group showed a significant result for functional reach test, the dynamic gait index, the 10-m walking test, the timed up-and-go test, and the Tai Chi group improved. In the quality of life, the therapeutic Tai Chi group showed a significant improvement in five items (physical function, pain, vitality, general health, mental health) among eight items in SF-36. This study confirmed that therapeutic Tai Chi influences the balance, gait, and life quality of stroke patients. Therefore, therapeutic Tai Chi can be used as an effective exercise in combination with general physical therapy to improve the balance, gait, and quality of life in stroke patients.

Association between symptoms of bilateral numbness and/or paresthesia in the feet and postural instability in Japanese patients with diabetes.

This study assessed the association between symptoms of bilateral numbness and/or paresthesia in the feet and postural instability in Japanese patients with diabetes. This cross-sectional study included 303 patients with diabetes, aged 40-88years, who were referred to an outpatient diabetic clinic between January and July 2013 at Shiga University of Medical Science Hospital. A posturography test was used to evaluate postural sway in patients. Indices of postural sway were the total length and the enveloped area. Analysis of covariance was used to estimate the multivariable-adjusted means of indices of postural sway according to the presence or absence of symptoms of bilateral numbness and/or paresthesia in the feet. Of 303 patients, 35 (11.6%) had symptoms of bilateral numbness and/or paresthesia in the feet. After adjustment for age, sex, diabetic retinopathy, regular exercise, body mass index, hemoglobin A1c level, and quadriceps' strength, patients with symptoms had higher levels of postural sway length and an enveloped area in the posturography test than those without symptoms. In addition, we observed similar results when we analyzed 234 patients aged ≥60years. Our findings suggest that patients who had symptoms of bilateral numbness and/or paresthesia in the feet may have more postural instability than those without symptoms.

The effect of face exploration on postural control in healthy children

The objective was to explore how face exploration affects postural control in healthy children. The novelty here is that eye movements and posture were simultaneously recorded. Three groups of children participated in the study: 12 children of 7.8±0.5 years old, 13 children of 10.4±0.5 years old and 12 children of 15.7±0.9 years old. Eye movements were recorded by video-oculography and postural stability was recorded by a platform. Children were invited to explore five emotional faces (neutral, happy, sad fear and angry). Analysis of eye movements was done on saccadic latency, percentage of exploration time spent and number of saccades for each specific region of interest (ROI): eyes, nose and mouth. Analysis of posture was made on surface area, sway length and mean velocity of the center of pressures (CoP). Results showed that visual strategies, exploration and postural control develop during childhood and adolescence. Indeed, after nine years-old, children started to look the eyes ROI firstly, then the nose ROI and finally the mouth ROI. The number of saccades decreased with the age of children. The percentage of exploration time spent in eyes ROI was longer than the others ROIs and greater for unpleasant faces (sad, fear and angry) with respect to pleasant emotional face (happy). We found that in front of sad and happy faces the surface area of the CoP was significantly larger compared to other faces (neutral and angry). These results suggest that visual strategies and postural control change during children's development and can be influenced by the emotional face.

The immediate effect of facilitation technique applied to the ankle joint on the balance ability in young healthy subjects

Background: The ankle joint stability is considered important component for the standing balance. Foot and ankle characteristics, such as ankle flexibility and strength, contribute to functional ability in elderly people. Therefore, improvement of the ankle joint stability is essential to obtain the better balance ability. Previously, a variety of approaches applied to the ankle joint to improve the standing balance have been investigated. However, the number of studies which explored the effect of the facilitation technique is few, although the techniques have been used in order to improve balance ability in the patients with neurological disorders. Purpose: The purpose of this study was to investigate the immediate effect of the facilitation technique applied to the ankle joint on the balance ability in young healthy subjects by comparing before and after the intervention. Methods:Nine young healthy subjects (fivemale and four female, 25.2± 1.0 ages, height 169.8± 7.8 cm, weight 59. 6± 7.1 kg) were recruited. The subjects who had orthopedic disease that could cause balance disability were excluded. A force platform (Gravicorder, Anima, Tokyo, Japan) was used to measure postural sway. The displacement of the center of pressure (COP) was measured at a 20Hz frequency. The subjects were asked to perform single leg stance with their right leg with their eyes open for 30 seconds and to look at a fixed eye-level target approximately 2m away before and after the intervention. The subjects were asked to sit on a chair, and keep their pelvis upright without leaning on the backrest during the intervention. A physiotherapist held and compressed the medial and lateral gastrocnemius muscle by their both hands and induces the plantarflexion with their forefoot on the floor 30 times. The total length of the body sway (LNG), the rectangle area (REC. area), the environmental area (ENV. area), the root mean square (RMS) and the root mean square area (RMS. area) were calculated as an indicator of the balance ability. A paired t-test was used for statistical analysis to compare the variables before and after interventions. The level of significance was set at p< 0.05. Results: There was a significant decrease of ENV.area, RMS and RMS.area (p< 005). However the values of LNG and REC. area did not show significant decrease. Conclusion(s): This result suggested the facilitation technique of the ankle joint could enable the participants to maintain one leg stance with smaller perturbation. The future research will be recommended to investigate the effect of this intervention on the balance ability in elderly people and patients with neurological disorders. Implications: The facilitation technique can be an effective approach for the improvement of the standing balance. This technique can be applied not only to elderly people but also the patients with neurological disorders who are not able to performvoluntarymovement of the ankle joint as voluntary movement of the joint is not required.

Analysis of the correlation between the differences in muscle strengths between the bilateral lower extremities and postural stability in healthy adults.

[Purpose] The purpose of this study was to examine the correlation between the differences in muscle strengths between the bilateral lower extremities and the level of postural sway that indicates postural stability. [Subjects and Methods] A total of 49 students (18 males and 31 females) at Y University in Gyeongsangnam-do, South Korea, participated in this study. Partial correlation analysis was performed to determine the effects of sway length and velocity on the differences in muscle strengths between the lower extremities. [Results] Both sway length and sway velocity showed a negative correlation with the difference in bilateral ankle dorsiflexion strength. Both sway length and sway velocity showed a positive correlation with the difference in bilateral hip flexion strength. [Conclusion] Difference in left-right muscle strengths of hip flexion and ankle dorsiflexion can affect postural stability when the levels of lower extremity muscle strengths are excluded.

The effect of Swiss ball exercise and resistance exercise on balancing ability of scoliosis patients.

[Purpose] The purpose of the study was to closely examine the efficiency of Swiss ball exercise and resistance exercise in improving the on the static balancing ability by applying them to patients with scoliosis and to compare the effects of the interventions. [Subjects] Forty scoliosis patients were divided into a Swiss ball exercise group (SEG, N = 20) and a Resistance exercise group (REG, N = 20) randomly. [Methods] SEG conducted chest stretching, trunk exercise using the Swiss ball. REG conducted chest stretching, trunk exercise with therapist’s resistance. Both groups received training 30 min per day, five times per week, for eight weeks. [Results] Both SEG and REG showed significant differences between pre- and post-mediation in terms of weight distribution, sway area, sway length, sway speed, and limit of stability. Sway speed and limit of stability had increased more significantly in REG than in SEG. [Conclusion] According to the result of this study, both Swiss ball exercise and chest Resistance exercise were effective for improving on the static balancing ability. But we suggest resistance exercise is more efficient to increase of sway speed, limit of stability.

The effects of virtual reality game exercise on balance and gait of the elderly.

[Purpose] The aim of this study was to examine the effects of ball exercise as a general exercise on the balance abilities of elderly individuals by comparing ball exercise with virtual reality exercise. [Subjects and Methods] Thirty elderly individuals residing in communities were randomly divided into a virtual reality game group and a ball exercise group and conducted exercise for 30 min 3 times a week for 8 weeks. [Results] Step length increased significantly, and the average sway speed and Timed Up and Go time significantly decreased in both groups. A comparison of sway length after the intervention between the two groups revealed that the virtual reality game exercise resulted in a reduction than the ball exercise. [Conclusion] The results of this study indicated that the virtual reality game exercise may improve balance and gait of elderly individuals in communities.

Stability of daily home-based measures of postural control over an 8-week period in highly functioning older adults.

The focus of this study was to monitor daily objective measures of standing postural control over an 8-week period, recorded in a person's home, in a population of healthy older adults. Establishing natural patterns of variation in the day-to-day signal, occurring in the relative absence of functional decline or disease, would enable us to determine thresholds for changes in postural control from baseline that could be considered clinically important. Eighteen community-dwelling older adults (3 M, 15 F, 72 ± 6 years) participated in a home-based trial where each day they were asked to complete a technology-enabled routine consisting of a short questionnaire, as well as a quiet standing balance trial. Centre of pressure (COP) excursions were calculated over the course of each daily balance trial to generate variables such as postural sway length and mean sway frequency. The data demonstrated large differences between subjects in centre of pressure measures (coefficients of variation ranging 37-107 %, depending on the variable). Each participant also exhibited variations in their day-to-day trials (e.g. coefficients of variation across 8 weeks ranging ~17-56 %, within person for mean COP distance). Inter- and intra-subject differences were not strongly related to functional tests, suggesting that these variations were not necessarily aberrant movement patterns, but are seemingly representative of natural movement variability. The idea of applying a group-focused approach at an individual level may result in misclassifying important changes for a particular individual. Early detection of deterioration can only be achieved through the creation of individual trajectories for each person, that are inherently self referential.

Comparison of postural control between healthy subjects and individuals with nonspecific low back pain during exposure to visual stimulus

Background Low back pain (LBP) is a common clinical problem. Many researchers have demonstrated that LBP disorders have difference in sensory strategies for postural control. Optokinetic stimulation (OKS) of optic flow has been widely applied to study its effect on vision, but has not been applied to LBP. Here we used OKS on different surfaces to investigate the characteristics of chronic nonspecific LBP (CNLBP) posture control, so as to provide new theoretical and experimental data for further recognizing CNLBP and enriching its treatment. Methods Fifteen individuals with CNLBP (age range 25–40 years) and 15 age and gender-matched control subjects were recruited. Each subject, while standing on a stable or soft surface, was exposed to random-dot patterns projected on a large screen, with the dots displaying expansion (+) and contraction (-) and velocities including 80°, 40°, and 20° per second. The visual stimulus used a “stimuli-interval” pattern. The peak velocity, different phases’ standard deviation (SD) of the anterior-posterior centre of pressure (COP) displacements and the total length of the medial-lateral COP sway (LML) for stable surface and soft surface were recorded by force platform. Results The main effect of surface on all parameters was significant, while the main effect of group and OKS showed no significance with the exception of peak velocity (F(3,95)=3.6, P=0.01) and A2 (F(5,140)=9.34, P &lt;0.01) for which the effect of OKS was significant. The interactions of group by OKS of A2 (F(5,140)=3.65, P &lt;0.01) and group by surface by OKS (F(5,140)=2.83, P=0.02), and surface by OKS of A1 and A3 (P &lt;0.05) were significant. It was reported that significantly more SD in amplitude in the T2 phase was seen in persons with CNLBP when confronting the + 40 stimuli on the soft surface (P &lt;0.05) compared to healthy individuals. Conclusions There was no significance between persons with CNLBP and healthy people when using the stable surface. Subjects with LBP showed decreased efficiency of postural adjustment when exposed to more complicated tasks and environments, especially OKS in the expansion direction, and displayed a visual-dependent phenomenon. This result suggested that the treatment of abnormal motor patterns in people with LBP should take the properties of task and environment into account.

Impaired postural balance in the morning in patients with knee osteoarthritis

Postural balance (PB) is frequently used as an outcome measure in clinical and research settings when assessing patients with knee osteoarthritis (OA). Pain and stiffness is known to affect PB, and is elevated in the morning and evening in OA patients. The aim of this study was to explore if time-of-day affects PB control in knee OA patients.Centre Of Pressure (COP) excursion was measured (100Hz) by force plate technique at selected time-points (9.00 a.m., 12.30 p.m. and 4.00 p.m.) during a single day in 32 knee OA patients aged 66.0 (10.3) years. A rigorous protocol was followed to ensure comparable testing conditions across time-points. PB control was quantified by the COP variables: velocity moment (mm2/s), total sway area (mm2), total sway length (mm) and confidence ellipse area (mm2).A two-way mixed-effects model showed that PB significantly improved between 9.00 a.m. and 12.30 p.m. in three out of four COP variables. The observed improvement was 11.9% (p=0.011) for velocity moment, 12.2% (p=0.011) for total sway area and 9.4% (p<0.001) for total sway length.PB appears to be impaired in the morning relative to midday in knee OA patients. Thus, it is recommended that time of assessment is standardized between sessions when assessing PB in clinical and research settings in knee OA patients.

The influence of peripheral neuropathy, gender, and obesity on the postural stability of patients with type 2 diabetes mellitus.

Aim. To assess the influence of peripheral neuropathy, gender, and obesity on the postural stability of patients with type 2 diabetes mellitus. Methods. 151 patients with no history of otology, neurology, or orthopaedic or balance disorders accepted to participate in the study. After a clinical interview and neuropathy assessment, postural stability was evaluated by static posturography (eyes open/closed on hard/soft surface) and the “Up & Go” test. Results. During static posturography, on hard surface, the length of sway was related to peripheral neuropathy, gender, age, and obesity; on soft surface, the length of sway was related to peripheral neuropathy, gender, and age, the influence of neuropathy was larger in males than in females, and closing the eyes increased further the difference between genders. The mean time to perform the “Up & Go” test was 11.6 ± 2.2 sec, with influence of peripheral neuropathy, gender, and age. Conclusion. In order to preserve the control of static upright posture during conditions with deficient sensory input, male patients with type 2 diabetes mellitus with no history of balance disorders may be more vulnerable than females, and obesity may decrease the static postural control in both males and females.

The Effects of Pilates Mat Exercise on the Balance Ability of Elderly Females

[Purpose] The purpose of this study was to examine the effects of Pilates exercise on a mat and balance exercise on an unstable base of support for trunk stability on the balance ability of elderly females. [Subjects and Methods] Forty elderly women aged 65 or older were equally assigned to a Pilates mat exercise (PME) group and an unstable support surface exercise (USSE) group. They conducted exercise three times per week for 12 weeks for 40 minutes each time. In order to examine balance, sway length and the speed of the center of foot pressure were measured for one minute, and in order to examine dynamic balance, the Timed Up and Go (TUG) test was conducted. [Results] After the intervention, sway length, sway speed, and TUG significantly decreased in both groups. A comparison of sway speed after the intervention between the two groups revealed that the PME group showed larger decreases than the USSE group. [Conclusion] PME and USSE elicited significant effects on the static and dynamic balance of elderly female subjects, suggesting that those exercises are effective at enhancing the balance ability of this group of subjects. However, the Pilates mat exercise is regarded as being safer than exercise on an unstable base of support.

Influence of pilates mat and apparatus exercises on pain and balance of businesswomen with chronic low back pain.

[Purpose] The purpose of this study was to examine the influence of mat Pilates and apparatus Pilates on pain and static balance of businesswomen with chronic back pain. [Subjects and Methods] Participants were randomly allocated to Pilates mat exercises (PME) or Pilates apparatus exercise (PAE), and performed the appropriate Pilates exercises 3 days per week for 8 weeks. In order to measure the improvement in the participants’ static balance ability as a result of the exercise, the sway length and sway velocity of the subjects were measured before and after the experiment while the subjects stood on a Balance Performance Monitor (BPM) facing the front wall for 30 seconds with their eyes open. The visual analogue scale (VAS) was used to measure the degree of pain. [Results] The VAS score, sway length, and sway velocity of both groups decreased significantly after the experiment, but the PME group showed a greater decrease than the PAE group. [Conclusion] PME showed greater improvement in pain level and balance compared with PAE in this research. Since the subjects of this study were patients with low back pain, PME is assumed to have been more suitable and effective because it uses body weight to strengthen core muscles rather than heavier apparatuses as in PAE.

The Effect of Trunk Stabilization Exercises Using a Sling on the Balance of Patients with Hemiplegia

[Purpose] The purpose of this study was to examine the effects of trunk stabilization exercise using a saing on the balance ability of patients with hemiplegia. [Subjects] Forty patients with hemiplegia resulting from stroke were divided into a sling exercise group (SEG, n=20) and a mat exercise group (MEG, n=20). [Methods] The SEG conducted the trunk stabilization exercise using a sling, and the MEG performed the trunk stabilization exercise on a mat. [Results] The balance ability of both groups significantly improved. Although there were no significant differences between the groups, the SEG showed a greater reduction in the sway area (SA) and the sway length (SL) of the center of the pressure compared to the MEG. [Conclusion] We recommend trunk stabilization exercise using a sling as a clinical intervention to improve the balance ability of patients with hemiplegia.

Relationship between Mental Rotation of Body Parts and Postural Stability during Quiet Stance

Abstract The present study was designed to investigate a relationship between the ability to quickly perform a mental rotation (MR) task using body (particularly foot) stimuli and postural stability during unipedal and bipedal quiet stance. Twenty-four healthy young adults participated in this study to measure reaction times for the MR (stimuli: foot, hand, and car), postural sway values during unipedal and bipedal standings, and lower extremity functions. Results showed significant correlations between the reaction time for the MR of the foot stimuli (but not for hand and car stimuli) and some of postural sway values (total length of sway and mean velocity in the anterior–posterior direction) during unipedal standing (but not for bipedal standing). Consistently, participants who performed the MR task quickly showed significantly smaller sway values during unipedal standing than those who performed the task slowly. These findings suggest that the ability to mentally imagine the foot movement is likely to relate to postural stability, while involving a challenging postural task, such as unipedal standing. The reaction time for the MR of foot stimuli was also correlated with two-point discrimination (TPD) distance on the plantar skin. Given that the TPD distance not only represents cutaneous acuity but also reflects participants’ body image relating to their feet, MR performance may have been related to postural stability because both involve cognitive processes used for both motor imagery and motor execution of the foot movement.