Lower Extremity Position Influence on the Postural Stability Index Registered by the Biodex Stability System (original) (raw)

Influence of knee position on the postural stability index registered by the Biodex Stability System

Gait & Posture, 2008

The importance of knee position for bodily stability is described by some authors, however Biodex Stability System (BSS) trials have not been used to assess the reliability and effects of different knee positions. The purposes of this study were to test the reliability of BSS indices using two knee positions in the measurement protocol (either permitting slight knee flexion or maintaining them locked in total extension) and to compare the BSS indices between these two knee positions. The measurements were taken of the Overall Stability Index (OSI), Anterior–Posterior Stability Index (APSI) and Medial–Lateral Stability Index (MLSI) during a 30 s protocol which gradually and automatically increased in difficulty among 21 healthy female subjects (22.8 ± 1.0 years old). The subjects performed four trials which, without visual feedback, permitted knee flexion as well as four trials which did not, in a randomized order. The first two trials in each set were used for familiarization only. Permitting slight flexion yielded better reliability results (OSI Intra-class Correlation Coefficient [ICC] = 0.93, APSI ICC = 0.90, MLSI ICC = 0.89) than maintaining the knee in total extension (OSI ICC = 0.88, APSI ICC = 0.87, MLSI ICC = 0.79), with good agreement in the Bland and Altman test. Moreover, permitted knee flexion in BSS presented better balance stability values for OSI (P = 0.001) and APSI (P = 0.024), however the MLSI did not present significant difference between positions (P = 0.345).

Postural stability index is a more valid measure of stability than equilibrium score

The Journal of Rehabilitation Research and Development, 2005

Researchers, therapists, and physicians often use equilibrium score (ES) from the Sensory Organization Test, a key test in the NeuroCom EquiTest System (a dynamic posturography system) to assess stability. ES reflects the overall coordination of the visual, proprioceptive, and vestibular systems for maintaining standing posture. In our earlier article, we proposed a new measure of anterior-posterior (A-P) postural stability called the Postural Stability Index (PSI), which accounts for more biomechanical aspects than ES. This article showed that PSI provides a clinically important adjunct to ES. In the present article, we show that PSI can provide an acceptable index even if a person falls during the trial, whereas ES assigns a zero score for any fall. We also show that PSI decreases as ankle stiffness increases, which is intuitive, while ES exhibits the opposite behavior. Ankle stiffness is generally recognized as an indicator of postural stability. These results suggest that PSI is a more valid measure of A-P stability than ES.

Effects of pronated and supinated foot postures on static and dynamic postural stability

Journal of athletic training, 2005

Context: The foot is the most distal segment in the lower extremity chain and represents a relatively small base of support on which the body maintains balance (particularly in single-leg stance). Although it seems reasonable that even minor biomechanical alterations in the support surface may influence postural-control strategies, the implications of a hypermobile or hypomobile foot on balance have received little attention to date.Objective: To determine if supinated and pronated foot types influence measures of static and dynamic balance.Design: Participants were assigned to 1 of 3 groups depending on foot type, as defined by navicular-drop measures: pronated (≥10 mm), neutral (5–9 mm), or supinated (≤4 mm). Measures of static and dynamic balance were obtained for each participant and compared across groups.Setting: Sports medicine and athletic training research laboratory.Patients or Other Participants: Sixteen individuals with pronated (navicular drop = 13.0 ± 3.7 mm), neutral (navicular drop = 6.2 ± 1.1 mm), or supinated (navicular drop = 2.2 ± 1.7 mm) foot postures volunteered to participate in the study.Main Outcome Measure(s): We used the Chattecx Balance System to measure center of balance, stability index, and postural sway during static single-limb stance under eyes-open and eyes-closed conditions. Center of balance was defined as the point on the foot at which the body weight was equally distributed between the medial-lateral and anterior-posterior quadrants and was recorded in centimeters. Stability index was defined as the mean deviation in sway around the center of balance. Postural sway was expressed as the maximum sway distance recorded (cm) in the medial-lateral and anterior-posterior directions. The Star Excursion Balance Test was used to measure dynamic balance, which was reported as the reach distance (cm) in each of the 8 directions tested. The average of 3 trials of each measure was calculated and normalized to the subject's height.Results: We found no difference in center of balance or postural sway as a function of foot type. The stability index was greater in pronators than in supinators, but neither group was different from those with neutral foot types. Dynamic reach differed among groups but only in some directions. Generally, pronators reached farther in the anterior and anterior medial directions and supinators reached farther in the posterior and posterio-lateral directions. In the lateral direction, supinators reached farther than pronators but not farther than neutrals.Conclusions: Our results suggest that postural stability is affected by foot type under both static and dynamic conditions. These differences appear to be related to structural differences as opposed to differences in peripheral input. These effects should be considered when clinicians use such balance measures to assess injury deficits and recovery.

Misalignment of the knees: Does it affect human stance stability

Journal of Bodywork and Movement Therapies, 2011

Introduction: Data describing the relationships between postural alignment and stance stability are scarce and controversial. Objective: The aim of this study was to evaluate the effects of sensory disturbances on knee alignment in upright stance and the effects of knee hyperextension on stance stability. Method: Kinetic and kinematic data of 23 healthy adult women were collected while quietly standing in four sensory conditions. Kinematic data: knee angle (dependent variables) variations were analyzed across sensory conditions. Kinetic data: as subjects with hyperextended knees showed a clear tendency to flex their knees as balance challenge increased, center of pressure (COP) parameters (dependent variables) were analyzed in each sensory condition among trial sub-groups: Aligned-Trials (knee angle < 180 ), Hyperextended-Trials (>180 ) and Adjusted-Trials (>180 initially, turned <180 under challenging conditions). Results: Differences were found in mean velocity of COP in two conditions showing that knee alignment can affect stance stability. Conclusion: Knee hyperextension is a transient condition changing under postural challenges. Knee hyperextension affected postural control as mean velocity was the highest in the hyperextended group in natural standing sensory condition and lowest with sensory disturbance. ª

An Evaluation of New Indices of Postural Sway in Patients with Knee Osteoarthritis

Journal of Babol University of Medical Sciences, 2017

BACKGROUND AND OBJECTIVE: Reduced joint proprioception plays an important role in the initiation and progression of the knee osteoarthritis. The present study aims to evaluate postural sway in three different positions and analyze its trends using relative indices. METHODS: This cross-sectional study was conducted among 34 patients with knee osteoarthritis and 12 healthy people using selective sampling and convenience sampling. In order to evaluate the static equilibrium indices, patients were asked to sit on the force plate in three positions; Comfort Double Leg Standing (CDLS), Romberg Standing (RS) and Near Tandem Standing (NTS). The relative values of RS and NTS were used to determine the changes in postural sway in RS and NTS positions relative to CDLS. FINDINGS: In CDLS position, the range and the standard deviation of lateral position in patients (0.019±0.010 and 0.003±0.001, respectively) was lower than healthy people (0.051±0.039 and 0.012±0.010, respectively). In this position, the displacement range in the anterior-posterior direction in patients (0.110±0.029) was also lower than healthy people (0.130±0.027). In RS position, standard deviation and the velocity of center of pressure displacement in the patients group (0.016±0.006 and 0.012±0.004, respectively) was significantly higher than healthy people (0.012±0.003 and 0.009±0.002, respectively). On the contrary, the ratio of RS and NTS values was higher in patients group. CONCLUSION: Results of the study demonstrated that patients with more difficult positions (RS, NTS) have more sways than those with CDLS, especially in the lateral direction. Therefore, balancing and strengthening exercises are especially important in the lateral direction and in challenging situations.

Development of Postural Stability Index to Distinguish Different Stability States

Entropy, 2019

A key factor for fall prevention involves understanding the pathophysiology of stability. This study proposes the postural stability index (PSI), which is a novel measure to quantify different stability states on healthy subjects. The results of the x-, y-, and z-axes of the acceleration signals were analyzed from 10 healthy young adults and 10 healthy older adults under three conditions as follows: Normal walking, walking with obstacles, and fall-like motions. The ensemble empirical mode decomposition (EEMD) was used to reconstruct the acceleration signal data. Wearable accelerometers were located on the ankles and knees of the subjects. The PSI indicated a decreasing trend of its values from normal walking to the fall-like motions. Free-walking data were used to determine the stability based on the PSI. The segmented free-walking data indicated changes in the stability states that suggested that the PSI is potentially helpful in quantifying gait stability.

Correlation of Static and Dynamic Balance with Knee Proprioception in Normals

International Journal of Physiotherapy and Research

Background: Human balance depends on coordinated integration of sensory input from somatosensory, vestibular and visual systems. Proprioception includes 3 components: sense of position, sense of movement and sense of force. Most of the injuries have the potential to decrease proprioception and subsequently balance. It is important to understand the relation between proprioception and balance in young adults. Thus this study aimed at co-relating static and dynamic balance with knee proprioception in Normals. Purpose of the study: To understand the correlation of balance with knee proprioception. Materials and Methods: Young asymptomatic adults (N=50),equal males (n=25) and females (n=25) between the age group of 18-30 years (mean age=21.2) were assessed for knee joint proprioception at 60 0 using universal goniometer, static balance using Balance Error Scoring System(BESS) and dynamic balance using Star excursion balance test (SEBT). Result: There is a weak negative correlation [r =-0.3161(rt) and r =-0.1599(lt)] of knee joint proprioception error with dynamic balance and a weak positive correlation [r = 0.3358(rt) and r = 0.2912(lt)] of knee joint proprioception error with static balance error. Conclusion: The study concludes that lesser the knee joint proprioception error better is the dynamic balance. And lesser the knee joint proprioception error lesser is the static balance error.

Assessing Static Postural Stability with Balance Error in Female Participants

lower limb muscle fatigue may impair the proprioceptive and kinesthetic properties of joints altering conscious joint awareness. the purpose of this study was to examine the effect of plantar flexor muscle fatigue on postural control. twenty-two female physical education students 21.00 ± 4.36 years old, with no history of injury in the last 6 months or pathology to either lower extremity volunteered to participate in this study. postural stability was measured using Bess; consisting of 6 conditions: double-leg stance, single-leg stance, and tandem stance which were performed on a firm surface and on a foam surface with the eyes closed. errors were counted during each 20-second trial. participants performed calf muscle fatiguing exercises on their dominant leg and used their other leg for control. their body sway was measured by them standing on one leg prior and following these fatiguing exercises. During the plantar flexor muscle fatigue protocol, the participants stood upright supporting on a raised surface with the front place of the sole on their dominate leg and were instructed to conduct as many concentric-eccentric ankle plantar flexor contractions

Postural stability in adults under 30 years of age

2015

Introduction. The aim of the present study is to determine the standard values of parameters describing postural stability: COP area, COP length and lower limbs loading symmetry index (SI). Material and Methods. 60 students of physiotherapy from the University School of Physical Education in Poznan participated in the study. In the case of 29 students, contraindications to participating in the study were identified. Ultimately, 31 participants were selected to take 30-second tests performed while standing on both feet, with and without visual control. Results. The standard values of the COP length parameter were determined. In the test with visual control, 6.5% of participants achieved high and very high scores. 87% achieved average scores. In the test without visual control, 9.7% of participants achieved high and very high scores, while 80.6% attained average scores. The SI index had a normal distribution. It showed that most people put the weight onto their left lower limb, both w...