Total Locus Length Research Articles

Wearing high-heeled shoes on a side slope makes standing balance unstable

IntroductionMany women wearing high-heeled footwear are at high risk of falls. Past studies have examined the balance on level ground or balance during walking. We measured the standing balance on the ground and side slopes for 18 healthy women. MethodBody sway was evaluated based on the center of pressure (COP) while participants stood on level ground on a side slope. The total locus length as well as rectangular and outer peripheral areas were then measured using a Zebris system. Measurements were compared under bare feet, normal shoe, and high-heeled shoe conditions. ResultsOn level ground, there were no significant differences among the three conditions. On the side slope, the total locus length (TLL), rectangular area (RA) and outer peripheral areas (OPA) were significantly greater for the high-heeled shoes than for the bare feet and normal shoes. Standing on the side slope caused larger body sway than on the level ground, along with a higher risk of falling. DiscussionIn TLL, OPA, and RA, the COP moved outside substantially when participants stood on a slope in high heels than in shoes. High heels were highly unstable for standing on a slope since the ankle joint of one leg is in plantar flexion, the foot is pronated, and the other side is plantarflexed at the ankle with pronation of the foot. ConclusionHigh-heeled shoes significantly alter a person's balance when standing on a side slope, suggesting a high risk of falling.

Physical effects of motion sickness for comfortable VR viewing

AbstractIn accordance with developments in the image technology over recent years, it has become easier to watch 3D video clips. As the viewing of 3D video has become more commonplace, symptoms such as visually induced motion sickness (VIMS) and eye fatigue have been reported. Although various theories regarding the underlying causes of the VIMS have been proposed, these causes have yet to be fully investigated. In a previous study, the background of an image was shown to influence the equilibrium function of a subject viewing a 3D video clip. In this study, the authors investigated the influence of image elements such as the size of the visual field especially in the backgrounds of the projected image and velocity of the visual target speed on the body of a subject viewing a 3D video clips by measuring their body sway, the electrocardiogram signals, and the cerebral blood flow using functional near‐infrared spectroscopy (fNIRS). Our results has indicated that the value of the total locus length is significantly higher while viewing a video clip whose visual fields of backgrounds is not narrowed than that with narrower backgrounds. This suggests that stability in the system to control their posture can be enhanced by reducing the amount of visual information.

Physical Effects of Motion Sickness for Comfortable VR Viewing

In accordance with developments in the image technology over recent years, it has become easier to watch 3D video clips. As the viewing of 3D video has become more commonplace, symptoms such as visually induced motion sickness (VIMS) and eye fatigue have been reported. Although various theories regarding the underlying causes of the VIMS have been proposed, these causes have yet to be fully investigated. In a previous study, the background of an image was shown to influence the equilibrium function of a subject viewing a 3D video clip. In this study, the authors investigated the influence of image elements such as the size of the visual field especially in the backgrounds of the projected image and velocity of the visual target speed on the body of a subject viewing a 3D video clips by measuring their body sway, the electrocardiogram signals, and the cerebral blood flow using functional near-infrared spectroscopy (fNIRS). Our results has indicated that the value of the total locus length is significantly higher while viewing a video clip whose visual fields of backgrounds is not narrowed than that with narrower backgrounds. This suggests that stability in the system to control their posture can be enhanced by reducing the amount of visual information.

Significance of Stabilometry for Assessing Postoperative Body Sway in Patients with Cervical Myelopathy.

Study DesignProspective study.PurposeTo examine the changes in body sway using stabilometry in patients who underwent cervical laminoplasty for cervical myelopathy.Overview of LiteratureAlthough the patients of cervical myelopathy complain body sway there are few report to examine body sway objectively.MethodsPatients who received treatment for cervical myelopathy between October 2010 and February 2013 were included. Twenty-one patients underwent cervical laminoplasty (myelopathy group). Body sway was assessed using stabilometry, wherein patients stood on a stabilometer with their eyes closed for 30 seconds. The Romberg ratio, outer peripheral area (OPA) with eyes closed (cm2), and total locus length per unit area (L/A) with eyes closed (/cm) were examined. Examinations were performed preoperatively (at baseline) and at 8 weeks postoperatively. Examination results of patients in the myelopathy group were compared with those of 17 healthy individuals (control group). Clinical symptoms were evaluated using the Japanese Orthopaedic Association scale score (JOA score) and the timed up and go (TUG) test.ResultsIn the myelopathy and control groups, the mean baseline Romberg ratio, OPA, and L/A were 2.3±1.2, 8.9±5.5 cm2, and 14.2±5.3/cm and 1.4±1.0, 4.3±2.8 cm2, and 23.7±10.1/cm, respectively. Eight weeks after laminoplasty, only L/A showed significant improvement from baseline in the myelopathy group (23.2±10.1 to 16.8±7.9; p=0.03). The Romberg ratio and OPA showed improvement in the myelopathy group, but the changes were not statistically significant. JOA scores and TUG test results in this group significantly improved from baseline to 8 weeks after laminoplasty (12.7 to 13.4 and 10.8 to 8.0 seconds, respectively; both p<0.05).ConclusionsL/A is a useful parameter for measuring body sway to assess the recovery of body sway after laminoplasty.

Influence of Transcranial Direct Current Stimulation to the Cerebellum on Standing Posture Control.

Damage to the vestibular cerebellum results in dysfunctional standing posture control. Patients with cerebellum dysfunction have a larger sway in the center of gravity while standing compared with healthy subjects. Transcranial direct current stimulation (tDCS) is a noninvasive technique for selectively exciting or inhibiting specific neural structures with potential applications in functional assessment and treatment of neural disorders. However, the specific stimulation parameters for influencing postural control have not been assessed. In this study, we investigated the influence of tDCS when applied over the cerebellum on standing posture control. Sixteen healthy subjects received tDCS (20 min, 2 mA) over the scalp 2 cm below the inion. In Experiment 1, all 16 subjects received tDCS under three stimulus conditions, Sham, Cathodal, and Anodal, in a random order with the second electrode placed on the forehead. In Experiment 2, five subjects received cathodal stimulation only with the second electrode placed over the right buccinator muscle. Center of gravity sway was measured twice for 60 s before and after tDCS in a standing posture with eyes open and legs closed, and average total locus length, locus length per second, rectangular area, and enveloped area were calculated. In Experiment 1, total locus length and locus length per second decreased significantly after cathodal stimulation but not after anodal or sham stimulation, while no tDCS condition influenced rectangular or enveloped areas. In Experiment 2, cathodal tDCS again significantly reduced total locus length and locus length per second but not rectangular and enveloped areas. The effects of tDCS on postural control are polarity-dependent, likely reflecting the selective excitation or inhibition of cerebellar Purkinje cells. Cathodal tDCS to the cerebellum of healthy subjects can alter body sway (velocity).

Relationships Between Toe-Grip Strength and Static and Dynamic Balance During Single-leg Stance

Postural control deficit is considered a factor for lower limb injuries in athletes, such as knee and ankle joint injuries, and in recent years, relationships have been suggested between toe-grip strength and static and dynamic balance. Female athletes have a higher incidence of knee and ankle joint injuries than males, especially in soccer, basketball, and lacrosse. PURPOSE: The purpose of this study was to examine the relationships between toe-grip strength and static and dynamic balance during single-leg stance in female collegiate lacrosse players. METHODS: Thirty-three female collegiate lacrosse players (mean age 19.3 ± 0.9 years, mean height 159.2 ± 5.4 cm, mean weight 55.3 ± 5.1 kg) participated in this study. Static balance was tested using a stabilometer by having participants maintain a single-leg stance for 30 s, with outcome measures including total locus length, total locus length per unit area and per unit time, and circumference and rectangular area of body sway. Dynamic balance was evaluated using three directions on the star excursion balance test (anterior, posteromedial, and posterolateral). Correlations between toe-grip strength and static and dynamic balance were determined using Pearson’s correlation coefficient. The unpaired t-test was used to compare athletes with greater and lesser toe-grip strength. Significance level was p < 0.05. RESULTS: Toe-grip strength of the right foot was significantly negatively correlated with total locus length and total locus length per unit time (r = −0.354, p = 0.043, respectively), and athletes with a strong right-foot toe-grip had significantly shorter total locus length and total locus length per unit time compared with those with a weak one (p = 0.043, respectively). Athletes with a strong left-foot toe-grip had significantly longer normalized anterior reach distance (reach distance divided by leg length and multiplied by 100) on the star excursion balance test compared to those with a weak one (p = 0.020). CONCLUSIONS: This study suggests that toe-grip strength in female collegiate lacrosse players is related to static and dynamic balance ability in the single-leg stance and that its measurement and evaluation may contribute to the prevention of lower limb injuries, such as knee and ankle joint injuries, among female athletes.

The Effect Of Tightrope Walking Exercises Once A Week For Two Weeks On Balance Factors

The ability to balance is an important, basic element required to improve actions, such as fall prevention in the elderly, skating, balance beam exercise, and tightrope walking. Validation studies conducted on factors affecting balance are divided in their opinions. PURPOSE: The aim of the present study was to elucidate the effect of tightrope walking exercise, performed for 2 min a week for 2 weeks, on the tightrope walking distance, total locus length, unit locus length, unit area locus length, and environmental area. METHODS: Subjects were 12 healthy males (Age: 23.8 ± 4.6 years, Height: 171.2 ± 5.8 cm, Weight: 65.3 ± 13.3 kg). For balance exercises, we attached a 400 cm-long rope at a height of 30 cm to rack, and tested the setup by traversing the tightrope for 2 min barefoot to ensure that there was no chance of slipping. The rope was flat, 5 cm wide, and 0.2 cm thick. Tightrope walking exercises were performed once a week for 2 weeks. To assess balance, we found the 15-s value for each postural sway item for two- and one-legged standing with the eyes open and closed using a stabilometer. Postural sway items were total locus length, unit locus length, unit area locus length, and environmental area. Numeric values are all expressed as the mean ± the standard deviation and comparisons of the values from before and after the exercise period were processed by the paired t-test. The level of significance was set at p<0.05. RESULTS: Tightrope walking distances increased significantly (p<0.05) from 219 ± 71 cm to 424 ± 210 cm following 2 weeks of tightrope walking exercise. During two-legged standing with the eyes closed, the total locus length and unit locus length significantly decreased (483.0 ± 76.9 mm to 437.8 ± 65.4 mm and 32.2 ± 5.1 mm to 29.2 ± 4.4 mm, p<0.05). During one-legged standing on the right leg with the eyes closed, a significant decrease was observed in both the total locus length and unit locus length (1525.2 ± 384.5 mm to 1168.2 ± 235.3 mm and 101.7 ± 25.6 mm to 77.9 ± 15.7 mm, p<0.05), whereas during one-legged standing on the left leg with the eyes open, unit area locus length significantly decreased (3.8 ± 0.8 mm to 3.0 ± 1.0 mm, p<0.05). CONCLUSIONS: Tightrope walking exercise affected both dynamic balance through tightrope walking and static balance through one-legged standing.

Possibility of Using the Wii Balance Board in Stabilometry

Stabilometry is useful for understanding overall equilibrium function, and is applied as one test of body equilibrium function. It is a simple test in which 60-second recording starts when body sway stabilizes. Objective evaluation is possible by computer analysis of the speed and direction of the sway, enabling diagnosis of a patient’s condition. However, conventional stabilometer are very expensive. Attempts have therefore been made to develop a method of stabilometry using a Wii Balance Board. Wii Balance Boards are available at much lower cost than conventional stabilometers. As an application of stabilometry using the Wii Balance Board, we conducted a stabilometry test with subjects viewing 3D images. In this study, we examined the possibility of stabilometry using a Wii Balance Board. We also examined the effect on equilibrium function of stabilometry done with subjects viewing 3D images. We compared conventional stabilometry and the Wii Balance Board. Among the four types of analysis index, a very high correlation was seen in total locus length between the two instruments. Total locus length was the only analysis index for which a strongly correlation was seen with conventional stabilometer. Therefore, it may be possible to use a Wii Balance Board in place of a conventional stabilometer using total locus length. We also performed stabilometry with subjects viewing a 3D image. The results of stabilometry performed with subjects viewing stereoscopic images suggest that the total locus length may be helpful in visually induced motion sickness. Ke yw ords: Stabilometry, Stabilograms, Romberg’s Posture, Stereoscopic Image

重心動揺計による動的平衡機能検査の試み (Foulage test)&lt;br&gt;&amp;mdash;めまい患者における検討&amp;mdash;

We previously reported on preparatory study for a new dynamic equilibrium examination, the “Foulage test” using normal subjects. This is a unique stepping test on a stabilometer, keeping both toes constantly in contact with the plate and lifting up only the heels alternately, BPM 120, 60 seconds, 120 steps, with eyes open and closed. The total locus length (L) and the environed area (A) are measured. We found a new equilibrium parameter FT (=120A/L). In order to evaluate how FT can measure body sway, we applied this examination to patients with dizziness. Two hundred forty six patients, 60 men, 186 women, 14 to 87 years old, mean of age was 59.2, were tested. According to the sway level, patients were classified into 4 groups from stable “level 0” to almost falling “level 3”. We analyzed FT and sway level of each group. FT increased gradually (p<0.05 Steel-Dwass test) concomitantly with the sway level. This study may establish the Foulage test as a possible new dynamic equilibrium examination.

Standing Balance on the Ground —The Influence of Flatfeet and Insoles

[Purpose] The aim of this study was to determine whether insoles change standing balance on the ground in normal and flat-footed subjects. [Subjects] Twenty subjects with flatfeet and 20 subjects with normal feet were included in this study. [Methods] Body sway was evaluated based on the center of pressure while subjects stood on the ground. Body sway was measured during upright standing with the feet 10 cm apart for 30 seconds. The total locus length and the area of body sway were then measured using a zebris system. Measurements were made under three sets of conditions: using BMZ insoles, which supported the cuboid; using Superfeet insoles, which supported the medial longitudinal arch; and with no insoles. [Results] The 3 insole conditions were compared. On level ground, the total locus length for the Superfeet insole was significantly less than those for the BMZ insole and no insole. [Conclusion] On level ground, Superfeet feet insoles were effective in stabilizing standing balance in both flat-footed and normal-footed subjects.

Evaluation of Body Sway in a Seated Posture after Alcohol Ingestion with an Aim to Evaluate Motion Sickness Caused by Three-Dimensional Images

A few studies have evaluated swaying motion of the body in the seated posture; however, these studies did not evaluate motion sickness caused by watching movies, traveling, etc. This study aimed to analyze stabilograms recorded while the individuals were seated. Stabilometry was performed on 7 healthy male subjects (age, 21–22 years) in the seated position 5 min before, and at 5-min intervals from 5 to 60 min after alcohol load. Alcohol caused a decrease in the cerebellar equilibrium function that controls the vestibulospinal reflex. We adjusted the degree of simulative effect on the human equilibrium function. The stabilograms of the test subjects were analyzed according to the area of sway, total locus length, and total locus length per unit area. We found that significant alcohol-induced changes in the sway values in the seated posture were similar to those in the upright posture.

Study of stabilometry during standing upright in patients with spinocerebellar degeneration: Appearance and significance of the dominant peak-frequency of 3Hz in body sway

Appearance of the dominant peak-frequency in body sways during standing was retrospectively investigated in patients with spinocerebellar degeneration (SCD). Subjects tested were 25 patients with SCD (16 men and 9 women, ranging in age from 25 to 80; mean 55.8±15.4 yr). The disease types comprised SCA3 (n=5), SCA 6 (n=3), MSA-C (n=12), and an unknown type (n=5). Stabilometry was performed in each patient, who was asked to stand upright with a closed stance, with eyes open and eyes closed, using Anima's stabilometer G6100. The sampling time was 50 ms (20Hz) and the correcting time was 60 s. The peak-frequency was measured based on the power spectrum using the maximum entropy method (MEM). Total locus length, envelope area and velocity-vector of movement of the center of foot-pressure were also measured.The first or main peak appeared in a low frequency range between 0.10 and 0.59Hz in most of the cases with eyes open and eyes closed. It was detected in the lateral direction in 24 patients of the total number (96.0%) and in the anterior-posterior direction in 22 patients of the total (88.0%).The body sway of a frequency of 3Hz was detected in 4 patients (16.0%). Among them, the peak in the lateral direction was observed in 2 (8.0%) with eyes open or closed (one with SCA 6 and one with an unknown disease type). The peak in the anterior-posterior direction was detected in 3 (12.0%) with eyes open or closed (one each with SCA 6, MSA-C and an unknown disease type); in these subjects, the values of the total locus length divided by envelope area were more than 40.The dominant peak-frequency of 3Hz in body sways during standing did not frequently appear in patients with SCD, but it is suggested to be one of characteristic balance disorders in the disease.

Exercise Focused on Multiarticular Movement to Improve Muscle Activity During Gait and Single-leg Standing for Participants with Hip Osteoarthritis by Using Electromyogram and Three-dimensional Motion Analysis

[Purpose] We investigated how two types of exercise affect walking and single-leg standing in people with hip osteoarthritis (OA) using surface electromyogram (EMG) and three-dimensional (3D) motion analysis system. [Subjects and Methods] Participants were 18 female diagnosed as having hip OA. We defined hip abduction movement with a tube band wrapped around the thigh as monoarticular- (Mono-) group and the group using resisted joint extension with rotation movement as multiarticular- (Multi-) group. EMG measured the activity of the gluteus maximus (GMax) and gluteus medius (GMed) of affected side during 10 meters gait and single-leg standing on affected side. 3D motion analysis calculated the total locus length (TL) of anterior superior iliac spine (ASIS) of affected side during single-leg standing. These results were analyzed by t-test. [Results] After each exercise, %IEMG of GMax in Mono-group showed a significant decrease during the stance phase. In Multi group, GMax and GMed were significantly increased during the stance phase, whereas GMax was significantly decreased during the swing phase. TL during single-leg standing in Multi group decreased significantly. [Conclusion] These results indicate that exercise focusing on multiarticular movement improves muscle activity and stability in relation to daily activities.

アルコール摂取時の重心動揺における決定論性の評価

Equilibrium function in the cerebellum (vestibulo-cerebellar system) is deteriorated by medicinal actions (MAs). In the Romberg posture, the center of gravity, which was measured every 50 msec by stabilometry, appeared to shift with alcohol ingestion. In the previous study, a locus in the center of gravity (statokinesigram) was converted to a value of statistical indices such as area of sway, total locus length, and locus length per unit area, although these indices could not always distinguish between the statokinesigrams sampled from 7 healthy young males presenting with and without MAs. This measurement was made with an AMTI force plate. In this study, a statistical index “translation error” was estimated in a d-dimensional embedding space in order to compare statokinesigrams recorded before and after the ingestion of doubly diluted brandy in 30 s (1≤d≤10). We succeeded in validating a stochastic differential equation as a mathematical model of the body sway. The randomness in the model was preserved after alcohol intake and significantly increased in the medial/lateral direction. Visual information referred by the control system of standing posture might be regarded as an external forcing associated with the MA. This method is considered to be useful to diagnose the disorders of the vestibulo-cerebellar system.

Influence of Teeth Clenching on the Bodily Equilibrium against Striking Weight Impact

Purpose: The purpose of this study was to elucidate the influence of teeth clenching on the head posture and body sway during an impact lord to the greater trochanter of the femur.Methods: The sternocleidomastoid muscle activities, head posture, and the total locus length of head movement and body sway during and in the absence of a striking weight impact under the resting position of the mandible and during 50% and 100% voluntary maximal clenching were analyzed.Results: 1) The activity of the sternocleidomastoid muscles increased with the teeth clenching force, and the increase was greater during a striking weight impact than that in the absence of a striking weight impact. 2) The decrease in the lateral bending and rotation angles of the neck observed during a striking weight impact was greater under the voluntary teeth clenching conditions as compared with that under the resting position of the mandible. 3) The total locus length of the head movement and body sway were shorter under the voluntary teeth clenching conditions as compared with that under the resting position of the mandible. 4) In contrast to the observations under the resting position of the mandible during a striking weight impact, the ratio of the total locus length of the head movement to that of the body sway under the voluntary teeth clenching during a striking weight impact decreased to the level noted under the resting position of the mandible in the absence of a striking weight impact.Conclusion: The results of this study suggest that teeth clenching stabilizes the head in cooperation with the activities of the sternocleidomastoid muscles, and prevents excessive head movement and body sway during a striking weight impact.

前庭神経炎の長期経過に関与する因子の検討

We previously reported that platform stabilometry was effective in evaluating the condition of patients with vestibular neuritis. In the present study, we increased the patient population (n = 31) and followed them up for long-term (253.5 +/- 36.5 days after admission) to determine factors influencing prognosis. We examined the stability of patients with vestibular neuritis using platform stabilometry at 5 time points: P1, (5.3 +/- 0.7 days after admission); P2, (22.2 +/- 1.2 days); P3, (73.2 +/- 2.5 days); P4, (159.2 +/- 9.2 days); and P5, (258.3 +/- 23.5 days). For some elements--the total length of locus and the area of surroundings with open or closed eyes--the total length of locus with open eyes decreased significantly (P<0.05) following disease amelioration. Important factors for improving elements of platform stabilometry in patients with vestibular neuritis were age, presence of upper respiratory infection, and the duration of nystagmus.

重心動揺における幾何学的な指標の物理学的意味 アルコール摂取時の解析

In this paper, we report our development of an analytical index on stabilometry to diagnose a decrease in the cerebellar equilibrium function controlling vestibulo-spinal reflex. We measured the sway of the center-of-gravity of the body with a stabilometer for seven healthy men aged 19 to 26 years, and also recorded statokinesigrams after alcoholic intake. We propose classification of these statokinesigrams under two groups, statokinesigrams before the intake and after it. Suzuki et al. (1996) standardized indices, area of sway, total locus length and other parameters, on stabilometry, however, it was difficult to classify statokinesigrams with those indices. Here, we introduce a new index, sparse density, into stabilometry. We show that sparse density is a useful and stable index for classification in accordance with non-parametric statistics. Although we expected a similar effect on the circulatory system by the alcoholic load, variation of these indices was more complex than the variation derived from the organs for the recovery from the standpoint of time. We also analyzed data by paying attention to the force acting on them, which generated the statokinesigrams. We especially turned our attention to singular points where statistically tiny or huge forces are exerted. We could pursue the sparse density with sum of local force that acted on the center-of-gravity. We concluded that sparse density depends upon the function for the control of the center-of-gravity of the body.

高齢者の重心動揺および頭部動揺の加齢変化

To evaluate quantitatively the chronological changes in equilibrium function in elderly persons, we investigated head movement (H. M. ) and movement of the body's center of gravity (M. C. G. ), using a cephalograph to record H. M., a strain-gauge platform to record M. C. G. and a technical computer. Seventy-five healthy subjects aged 30 to 91 years were instructed to stand with feet close together on the platform with eyes open and then with eyes closed for periods of 60 seconds each. The results were as follows:1) The area and total length of locus traced by H. M. increased with age. Both were significantly greater in subjects older than 50 years of age than in younger adults under 40 years.2) The area and total length of locus traced by M. C. G. also increased with age. Measurements were significantly greater in subjects older than 70 years of age than in younger adults under 40years.3) The ratio of the anteroposterior component to the lateral component in H. M. did not differ between the age groups. This ratio for the M. C. G. with eyes open was however, significantly greater in subjects older than 70 years of age than in younger adults.4) The ratio of the total length of locus traced by H. M. to that of M. C. G. did not differ among the age groups.5) The ratio of the total length of locus traced by H. M. and M. C. G. with eyes closed to that with eyes open did not differ among the age groups. These results suggest that the body sway of the elderly is not only larger than that of younger adults, but is also fundamentally different in nature.

重心動揺検査 単位面積軌跡長の意義 健常者における検討

The purpose of this study is to make clear the significance of locus length per unit area (total locus length/ area of sway, L/A) as a parameter of stabilometry. We examined 100 healthy subjects aged 6 to 73 years. The subject stands on a stabilometer with eyes open or closed, and the sway of the center of gravity of the body is recorded for one minute. The pattern and area of sway, total locus length, L/A, Romberg's coefficient and power spectrum are recorded, and the L/A and other parameters are correlated.1) The L/A with eyes closed was low in those less than 20 years of age, higher at age 20 to 50. After age 60, these were some individual differences.2) The values of L/A with eyes closed were similar to those with eyes open.3) The L/A showed a negative correlation with the area of sway and the RMS.4) The L/A was not related to total locus length or Romberg's coefficient.5) Subjects with a high L/A had a high density power spectrum at 2-5 Hz.These findings show that L/A is a parameter of the fine control of standing posture by proprioceptive reflexes. The L/A is useful in the examination of the regulation of stan-ding posture.