Anterior-posterior Postural Sway Research Articles

Human balance augmentation via a supernumerary robotic tail.

Humans are intrinsically unstable in quiet stance from a rigid body system viewpoint; however, they maintain balance thanks to neuro-muscular sensory properties whilst still exhibiting postural sway characteristics. This work intro-duces a one-degree-of-freedom supernumerary tail for balance augmentation in the sagittal plane to negate anterior-posterior postural sway. Simulations showed that the tail could success-fully balance a human with impaired ankle stiffness and neural control. Insights into tail design and control were made; namely, to minimise muscular load the tail must have a significant component in the direction of the muscle, mounting location of the tail is significant in maximising inertial properties for balance augmentation and that adaptive control of the tail will be best suited for different loads held by a wearer.

Utility of a Postural Stability/Perceptual Inhibition Dual Task for Identifying Concussion in Adolescents.

Research in the area of dual-task paradigms to assess sport-related concussion (SRC) status is growing, but additional assessment of this paradigm in adolescents is warranted. This case-control study compared 49 adolescent athletes aged 12-20 years with diagnosed SRC to 49 age- and sex-matched controls on visual-spatial discrimination and perceptual inhibition (PIT) reaction time tasks performed while balancing on floor/foam pad conditions. The SRC group completed measures at a single time point between 1 and 10 days postinjury. Primary outcomes were dual-task reaction time, accuracy, and sway. General linear models evaluated differences between groups (P < .05). Logistic regression identified predictors of concussion from outcomes. Area under the curve evaluated discriminative ability of identifying SRC. Results supported significantly higher anterior-posterior (AP) sway values in concussed participants for visual-spatial discrimination and PIT when balancing on the floor (P = .03) and foam pad (P = .03), as well as mediolateral sway values on the floor during visual-spatial discrimination (P = .01). Logistic regression analysis (R2 = .15; P = .001) of all dual-task outcomes identified AP postural sway during the PIT foam dual task as the only significant predictor of concussed status (ß = -2.4; P = .004). Total symptoms (area under the curve = 0.87; P < .001) and AP postural sway on foam (area under the curve = 0.70; P = .001) differentiated concussed from controls. The AP postural sway on foam during a postural stability/PIT dual task can identify concussion in adolescents between 1 and 10 days from injury.

A biomechanical analysis of active vs static office chair designs

The objective of this study was to provide a biomechanical comparison of two different types of active chairs (AC1 & AC2) versus a static chair (NAC). Thirty healthy participants were recruited: fifteen healthy females and fifteen healthy males. Participants worked at a computer workstation (1-h per chair). Equipment included: Pressure pads, Electromyography, Near–Infrared Spectroscopy, and Questionnaires (rate of perceived discomfort, seating discomfort questionnaire and exit survey). A significant increase in anterior–posterior postural sway was found on the seat pan with the use of the AC1. An increase in neuromuscular activity of the external obliques and an increase change in total oxygen index (%TOI) values in the gastrocnemius were also found using the AC1, however the difference was not much higher than the NAC and AC2. Lower discomfort scores in the gluteal area were found with the use of active chair AC1 compared to the NAC. Preliminary findings suggest that having an office chair with a split seat pan design shows potential to yield biomechanical and physiological benefits for the sitter, however further research is needed to better understand the ergonomic benefits of active sitting.

Review of Forward-Head Posture and Vestibular Deficits in Older Adults

Forward-head posture (FHP) is a common postural deviation associated with older age, cervical muscle weakness, poor balance, anteriorly displaced center of mass, increased postural sway and fall risk, impaired cervical proprioception, and possibly vestibular dysfunction. Studies have found increased fall risk in older adults with FHP but have not identified a casual reason for this relationship. This review aims to examine the links between (FHP) and vestibular deficits. While assessment of overall posture, including FHP, is a common component of a physical therapy evaluation, a standardized method of clinical measurement for FHP is lacking. The craniovertebral angle (CVA) appears to be the most reliable method, with FHP defined as less than or equal to 44–53 degrees. Studies where FHP is measured using the CVA appear to be more accurate in identifying associations between this postural deviation and factors that impact postural control in older adults, such as balance and cervical proprioception. Limited studies have found FHP to be associated with duration of clinical symptoms of vestibular disease. FHP also heightens age-related increases in anterior-posterior postural sway. Compelling evidence exists that links FHP with vestibular deficits, increased fall risk, and impaired cervical proprioception. Further research using CVA and a consistent definition of FHP is needed to answer this question and develop clinical practice guidelines.

Using Accelerometers to Record Postural Sway in Adolescents With Concussion: A Cross-Sectional Study.

To investigate the magnitude of postural sway induced by different balance tasks in adolescents with concussion and to examine the associations of postural sway with concussion symptoms. Cross-sectional study. Fifty-six adolescents (20 girls, 36 boys) between 13 and 17 years of age who sustained a concussion within the past 44 days and were still symptomatic. Anterior-posterior postural sway was measured using an accelerometer attached to the participant's lower back while he or she performed 6 static-balance tasks that varied the visual input, type of surface, and foot stance. Participants self-reported symptoms that occurred at the time of the concussion (eg, dizziness, confusion, amnesia) as well as at the time of balance testing (eg, eye and head movement-induced dizziness). The normalized path length of postural sway during the different balance tasks was greater with the eyes closed (mean = 19.3 mG/s) compared with the eyes open (mean = 12.4 mG/s; P < .001). Furthermore, sway while standing with the feet together on a foam surface (mean = 17.9 mG/s) or while tandem standing on a firm surface (mean = 19.4 mG/s) was greater than sway while standing with the feet together on a firm surface (mean = 10.3 mG/s; P < .001). Greater sway was associated with dizziness and confusion reported at the time of injury ( P < .05). Dizziness and headache symptoms at rest were positively correlated with sway ( P < .05). Using accelerometers to measure postural sway during different challenging balance conditions in adolescents with concussion may provide an objective means of quantifying balance impairments in clinical environments. Furthermore, the association of these measurements with symptoms suggests a need to account for symptom severity at the time of testing.

Trunk forward flexion mobility in reference to postural sway in women after delivery: A prospective longitudinal comparison between early pregnancy and 2- and 6-month postpartum follow-ups

BackgroundIt has been documented that pregnancy-related increased connective tissue laxity may persist postpartum; however, it is still unclear for how long. This longitudinal study aimed to compare total trunk forward flexion mobility in women between their first trimester of pregnancy and at 2- and 6-month postpartum follow-ups. We also searched for a correlation between women's trunk flexibility and their postural stability in the sagittal plane. MethodsSeventeen healthy women participated in the study. Data were collected at their 7–12 weeks gestation appointments and at 6–10 and 25–28 weeks postpartum. At each session, the women performed a finger floor distance test, and data were collected on their waist circumference and BMI. The women's center of foot pressure mean velocity in the anterior-posterior direction was computed from 30-s long quiet-standing trials on a stationary force plate. FindingsTotal trunk forward flexion mobility was significantly higher at 2 and 6 months postpartum compared to that in early pregnancy (P < 0.05). At 6 months postpartum, a moderate negative correlation between finger floor distance test values and their anterior-posterior center of foot pressure mean velocity was observed (r = −0.6, P < 0.05). InterpretationIncreased total trunk flexibility may be present in women 6 months postpartum. During that period, women with higher trunk flexibility may be more likely to present higher anterior-posterior postural sway velocity in quiet standing.

Changes in gait and posture as factors of dynamic stability during walking in pregnancy

Changes in gait and postural control during pregnancy may lead to increased fall rates during walking relative to non-pregnant women. Due to lack of empirical evidence on balance and postural control in dynamic conditions, the primary aim of this study was investigate the changes in gait and postural control as factors of stability during walking. Gait and posture of thirty-five (35) pregnant women (27 ± 6.1 years) were analysed at self-selected walking speed, and at different stage of pregnancy. The results indicate that although the gait kinematics did not differ between the trimesters, significant associations were noted between the step width, the lateral trunk lean, and the medio-lateral deviations in centre of gravity and centre of pressure. In contrast to the static conditions, anterior-posterior postural sway is not present during walking, whereas the lateral trunk lean is the primary factor women use in pregnancy to keep the centre of gravity closer to the base of support. Postural changes and those in gait kinematics were largely affected by the relative mass gain, rather than the absolute mass. Considering the importance of relative mass gain, more attention during healthy pregnancy should be given to monitoring the timing of onset of musculoskeletal changes, and design of antenatal exercise programs targeting core strength and pelvic stability.

Postural Stability of Patients with Schizophrenia during Challenging Sensory Conditions: Implication of Sensory Integration for Postural Control.

Postural dysfunctions are prevalent in patients with schizophrenia and affect their daily life and ability to work. In addition, sensory functions and sensory integration that are crucial for postural control are also compromised. This study intended to examine how patients with schizophrenia coordinate multiple sensory systems to maintain postural stability in dynamic sensory conditions. Twenty-nine patients with schizophrenia and 32 control subjects were recruited. Postural stability of the participants was examined in six sensory conditions of different level of congruency of multiple sensory information, which was based on combinations of correct, removed, or conflicting sensory inputs from visual, somatosensory, and vestibular systems. The excursion of the center of pressure was measured by posturography. Equilibrium scores were derived to indicate the range of anterior-posterior (AP) postural sway, and sensory ratios were calculated to explore ability to use sensory information to maintain balance. The overall AP postural sway was significantly larger for patients with schizophrenia compared to the controls [patients (69.62±8.99); controls (76.53±7.47); t1,59 = -3.28, p<0.001]. The results of mixed-model ANOVAs showed a significant interaction between the group and sensory conditions [F5,295 = 5.55, p<0.001]. Further analysis indicated that AP postural sway was significantly larger for patients compared to the controls in conditions containing unreliable somatosensory information either with visual deprivation or with conflicting visual information. Sensory ratios were not significantly different between groups, although small and non-significant difference in inefficiency to utilize vestibular information was also noted. No significant correlations were found between postural stability and clinical characteristics. To sum up, patients with schizophrenia showed increased postural sway and a higher rate of falls during challenging sensory conditions, which was independent of clinical characteristics. Patients further demonstrated similar pattern and level of utilizing sensory information to maintain balance compared to the controls.

Effects of air bottle design on postural control of firefighters

The purpose of this study was to investigate the effect of firefighter's self-contained breathing apparatus (SCBA) air bottle design and vision on postural control of firefighters. Twenty-four firefighters were tested using four 30-minute SCBA bottle designs that varied by mass and size. Postural sway measures were collected using a forceplate under two visual conditions (eyes open and closed) and two stance conditions (quiet and perturbed stances). For perturbed stance, a mild backward impulsive pull at the waist was applied. In addition to examining center of pressure postural sway measures for both stance conditions, a robustness measure was assessed for the perturbation condition. The results suggest that wearing heavy bottles significantly increased excursion and randomness of postural sway only in medial-lateral direction but not in anterior-posterior direction. This result may be due to stiffening of plantar-flexor muscles. A significant interaction was obtained between SCBA bottle design and vision in anterior-posterior postural sway, suggesting that wearing heavy and large SCBA air bottles can significantly threaten postural stability in AP direction in the absence of vision. SCBA bottle should be redesigned with reduced weight, smaller height, and COM closer to the body of the firefighters. Firefighters should also widen their stance width when wearing heavy PPE with SCBA.

The development of an accelerometer-based measure of human upright static anterior-posterior postural sway under various sensory conditions: Test–retest reliability, scoring and preliminary validity of the Balance Accelerometry Measure (BAM)

Accelerometers are being used to assess postural control in adults, but there is little to support their reliability and validity. To estimate the test-retest reliability of the balance accelerometry measure (BAM) and to describe the known-groups validity of the BAM composite score. Two measures of standing postural sway were taken across six sensory (vision/stance surface) and motor stance (feet together or tandem) positions from eighteen patients with vestibular disorders and 84 healthy subjects. Test-retest reliability for postural sway was estimated across all conditions using intraclass correlation coefficient (ICC). A composite measure of sway standardized to young healthy subjects on eyes open firm surface stance was compared between groups. Test-retest reliability of postural sway was good (ICC ⩾ 0.74) under all sensory conditions except eyes closed/tandem stance, which was slight to poor. Analysis of the receiver operating characteristic curve for composite scores indicated significant accuracy at identification of subjects in the vestibular/balance disorder groups. Composite standard scores equal or greater than 21.1 identified subjects with vestibular disorders with an accuracy of 72% sensitivity and 68% specificity. The BAM displays good-excellent reliability for five of six sensory-motor conditions. The composite score appears to differentiate healthy from subjects with vestibular disorders.

Children's postural sway in response to low- and high-frequency visual information for oscillation.

Two experiments examined postural responses of 3- to 6-year-old children to visual information for oscillation. In Experiment 1, children saw oscillations of the surround, with these movements ranging in frequency between 0.2 and 0.8 Hz. Analyses of anterior-posterior postural sway revealed that, similar to previous developmental investigations, the frequency of sway matched the frequency of oscillations. Analyses of sway amplitude and timing, however, revealed patterns of results more in keeping with research on adults. Experiment 2 extended these findings, presenting oscillations in which the frequency changed during the trial. Analyses of anterior-posterior sway revealed that sway frequency matched both speeds of movement. In contrast, amplitude and timing measures were again in line with adult data. These results suggest that the postural sway of children contains both adultlike and nonadult-like parameters of balance control.

Characteristics of postural instability induced by ischemic blocking of leg afferents.

After minimizing proprioceptive input from the legs by ischemia without degradation of muscle force and excluding visual stabilization by eye closure, a characteristic anterior-posterior postural sway around 1 Hz was observed in three normal subjects. This is similar to the instability seen in two tabes dorsalis patients. From the spectral analysis of head and hip movements, displacements of the center of force and of ankle angle as well as from EMG recordings of the anterior tibial and gastrocnemius muscle it is concluded that the oscillations around 1 Hz are due to the long latency and high threshold of vestibularly induced leg muscle discharges (200-300 ms) arriving in the counterbalancing phase of the trunk, which causes an overshoot in body sway.