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Purpose：Mouthguards are used by athletes to help improve athletic performance. This study examined the effects of changes in occlusal condition with a mouthguard. Method：The subjects were junior reinforcement designated archery athletes，（18 years old, 3 females）who were tested on a Balance Master. The balancing indices measured included sway velocity（SV）and limits of stability（LOS）. Results：The difference in sway velocity parameters decreased after wearing a mouthguard for 2 months, whereas the movement velocity increased after wearing for 2 months. Endo Point Excursion and Maximum Excursion approached the target point when wearing a mouthguard. Conclusions：It is thought that these results were because the feeling of strangeness had decreased after wearing a mouthguard for 2 months. [ABSTRACT FROM AUTHOR]

Background Limited research exists on the effects of both high and low frequency whole body vibration (WBV) on individuals with subacute lateral ankle sprains. Hypothesis/Purpose To examine the difference in the effects of high and low frequency WBV on limits of stability (LOS) in adults with a subacute ankle sprain. It was hypothesized that WBV would improve effects on outcome variables for LOS as a component of dynamic balance. Study Design Quasi-experimental, pretest-posttest design. Methods Fifteen participants ages 19-27 years (Mean age 22±2.36) with either a Grade I or Grade II lateral ankle sprain received WBV in bilateral stance under three randomized conditions (high frequency-25 Hz, low frequency-6 Hz, and control, which consisted of bilateral stance with machine off) for six minutes over three sessions (one time per week). The LOS test, consisting of 5 variables, were assessed using the NeuroCom® Balance Manager-SMART EquiTest® (Natus Medical Incorporated, Pleasanton, CA) at baseline and after the intervention period. The participants completed a practice LOS test and then had a six-minute standing rest break. After the rest break, they completed the pre-LOS (baseline) test. Intervention was administered using the Galileo® Med L Chip Research (Novotec Medical GmbH, Pforzheim, Germany) for six minutes for the appropriate condition of either high or low frequency WBV or control. Data analysis was performed using 2-Way (2x3) Repeated Measures ANOVAs with additional post hoc testing as needed. Results Significant interactions were found for reaction time (RT), movement velocity (MVL), and maximal excursion (MXE) composite scores with a decrease in RT of 0.117 seconds (p=0.022) between control and high frequency conditions during the post LOS. For composite MVL, an increase of 0.547 degrees/second (p=0.002) between pre- and post-high frequency WBV occurred. For composite MXE, an increase of 2.13% p=0.031 (when comparing pre- and post-high frequency WBV. Conclusion Findings suggest that a single session of high frequency WBV in individuals with a subacute lateral ankle sprain may result in improvement in several components of postural stability. WBV is a quick intervention that could be implemented in physical therapy clinics, athletic training rooms, and workout facilities to improve an individual's LOS as a component of dynamic balance one to eight weeks post lateral ankle sprain. [ABSTRACT FROM AUTHOR]

Abstract Objective To assess whether variables from a postural control test relate to and predict falls efficacy in prosthesis users. Design Twelve-month within- and between-participants repeated measures design. Participants performed the limits of stability (LOS) test protocol at study baseline and at 6-month follow-up. Participants also completed the Falls Efficacy Scale-International (FES-I) questionnaire, reflecting the fear of falling, and reported the number of falls monthly between study baseline and 6-month follow-up, and additionally at 9- and 12-month follow-ups. Setting University biomechanics laboratories. Participants Participants (N=24) included a group of active unilateral transtibial prosthesis users of primarily traumatic etiology (n=12) with at least 1 year of prosthetic experience and age- and sex-matched control participants (n=12). Interventions Not applicable. Main Outcome Measures Postural control variables derived from center of pressure data obtained during the LOS test, which was performed on and reported by the Neurocom Pro Balance Master, namely reaction time, movement velocity (MVL), endpoint excursion (EPE), maximum excursion (MXE), and directional control (DCL). Number of falls and total FES-I scores. Results During the study period, the prosthesis users group had higher FES-I scores (U =33.5, P =.02), but experienced a similar number of falls, compared to the control group. Increased FES-I scores were associated with decreased EPE (r = −0.73, P=.02), MXE (r = −0.83, P<.01) and MVL (r = −0.7, P=.03) in the prosthesis users group, and DCL (r = −0.82, P<.01) in the control group, all in the backward direction. Conclusions Study baseline measures of postural control, in the backward direction only, are related to and potentially predictive of subsequent 6-month FES-I scores in relatively mobile and experienced prosthesis users. [ABSTRACT FROM AUTHOR]

Balance impairment, frequent in Multiple Sclerosis patients (MS), is difficult to detect promptly with routine clinical examination. Computerized platforms can measure subtle deficit but, given the complexity of postural system, multiple tests should be adopted. To evaluate whether platform was more sensitive than Romberg Test (RT) in detecting balance abnormalities, we 1) chose a battery of posturographic tests, 2) collected normative data from 58 healthy subjects 3) applied the tests to Clinically Isolated Syndrome (n=42) and minimally impaired MS (n=76). Subjects underwent 3 trials of quiet standing with eyes open and closed (modified Clinical Test of Sensory Interaction on Balance, mCTSIB) and 4 trials of voluntary anterior and lateral maximal leaning on right and left sides (Limits of Stability, LOS), giving 10 postural indexes. For every subject, the best trials were selected for subsequent analysis. Normative values were established in a range from 1st to 99th percentile, defining balance impairment by the presence of at least 2 indexes out of range. Even adopting the above mentioned strict definition of balance impairment, the forceplate resulted more sensitive than RT, detecting abnormalities in 25% of patients, while RT was abnormal in 7% only. In RT-negative patients with 1-year follow-up (n =67) the detection of a single abnormal index was able to predict a subsequent onset of symptomatic balance impairment. The proposed procedure is quick, easy to perform and can improve the assessment of the clinical course of MS, from a pre-clinical stage up to medium degree of disability. [ABSTRACT FROM AUTHOR]

Background: Stability and balance are fundamental during static and dynamic activities. The effects of wearing rocker bottom sole (RBS) shoes on the limits of stability (LOS) and adaptation to wearing RBS shoes need to be investigated. The objectives of this study were to evaluate the LOS when wearing RBS shoes, and to evaluate if people improve their stability while wearing RBS shoes over time. Methods: Eleven female subjects with no lower extremity impairments participated in the study. The LOS were tested at baseline and weeks 3 and 6 using a Neurocom SMART EquiTest equipment. Center of pressure (CoP) was determined using force plates, and tbe center of gravity (CoG) position was estimated from the CoP measures and subjects' anthropometry. Subjects performed a series of tasks that involved leaning in different directions so as to move the vertical projection of their CoG. End-point excursions of the CoG floor projection were calculated as a percentage of the distance between the starting position and the target. Considering the body as an inverted pendulum, we recorded the average angular velocity of the inverted pendulum during the movements and quantified directional control as a percentage of movement toward versus away from the target. Shoe types were compared using paired t tests, and sessions were compared using repeated measures ANOVA. Results: The angular velocities of the inverted pendulum (ie, CoG velocity) were not significantly different between shoe conditions in the front and back directions at baseline (4 ± 3 with RBS vs 5 ± 2 deg/sec with regular shoes, and 4 ± I vs 6 ± 4 deg/sec). Front directional control of the CoG was significantly worse with RBS shoes at weeks 3 and 6 (P < .015). Front end-point excursions were also lower with RBS shoes both at baseline and week 6 (P < .014). There were no significant changes over time. Conclusion: The findings indicate that the LOS were negatively affected by wearing RBS shoes and that people do not improve their stability while wearing these shoes even after a 6-week period of use. Clinical Relevance: This study shows that wearing RBS shoes increase instability and the instability remains even after wearing these shoes for six weeks. [ABSTRACT FROM AUTHOR]

Limits of stability are a well-known and practical way of looking into the problem of parametric resonance. In the present paper an in-depth analysis of parametric rolling is presented employing the concept of limits of stability as a tool for improved understanding and assessment of the complex dynamics embedded in the problem of non-linearly coupled parametric rolling in extreme regular seas. A third-order coupled mathematical model is considered. The coupled modes of heave, roll, and pitch are contemplated. By means of the analysis of the linear variational equation derived from the extended third-order model, the appearance of super-harmonics and increased rigidity - proportional to wave amplitude squared - due to third-order terms is demonstrated. The mathematical model is then cast in the form of a Hill's equation. Two important new aspects are addressed: the possible appearance of upper limits to the unstable area of the diagram; and the computation of numerical limits of stability. These new limits are compared with the analytical results. Subsequently, by computing the bifurcation diagrams, the dependence of the limits of stability on the initial conditions is shown. Finally, the basins of attraction corresponding to two internal regions of the domain of unstable motions are computed. [ABSTRACT FROM AUTHOR]