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Cyril Burdet and Patrice Rougier

To question the relation between uni- and bipedal postural skills, 21 subjects were required to stand on a force platform through uni- and bipedal conditions. These two protocols are commonly used paradigms to assess the balance capacities of healthy and disabled patients. The recorded displacements of the center of pressure (CP) were decomposed along mediolateral and anteroposterior axes and assessed through variance positions and parameters obtained from fractional Brownian motion (fBm) modeling to determine the nature and the spatiotemporal organization of the successive controlling mechanisms. The variances underline the relative independence of the two tasks. Nevertheless, as highlighted by the fBm framework, postural correction is initiated for the unipedal stance after shorter time delays and longer covered distances. When compared to bipedal standing, one of the main characteristics of unipedal standing is to induce better-controlled CP trajectories, as deduced from the scaling regimes computed from the fBm modeling. Lastly, the control of the CP trajectories during the shortest time intervals along the anteroposterior axis appears identical for both uni- and bipedal conditions. Unipedal and bipedal standing controls should thus be viewed as two complementary tasks, each providing specific and complementary insights into the postural control organization.

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James L. Croft, Vinzenz von Tscharner and Ronald F. Zernicke

Compliant surfaces are used to challenge postural stability, but assessments are frequently limited to summary measures of center of pressure that do not provide insights into the temporal dynamics of motor coordination. Here, we measured center-of-pressure changes on three surfaces (solid, foam, and air-filled disc) and quantified the relative timing of changes in joint angles and muscle activity with respect to center-of-pressure changes. Nine active male subjects (20–30 years old) performed ten 30-s trials of unipedal stance on each of the three surfaces. Sway range, mean sway, mean sway velocity, path length, and fitted ellipse area increased, monotonically, from solid surface to foam to air-filled disc. The number of significant cross-correlations was greater for the compliant surfaces compared with the solid surface. Muscle activity preceded changes in center-of-pressure displacement, with the type of surface affecting the magnitude of the lead in the mediolateral direction. Center of pressure was more constrained on less stable surfaces and in the mediolateral direction.

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Nooranida Arifin, Noor Azuan Abu Osman and Wan Abu Bakar Wan Abas

The measurements of postural balance often involve measurement error, which affects the analysis and interpretation of the outcomes. In most of the existing clinical rehabilitation research, the ability to produce reliable measures is a prerequisite for an accurate assessment of an intervention after a period of time. Although clinical balance assessment has been performed in previous study, none has determined the intrarater test-retest reliability of static and dynamic stability indexes during dominant single stance. In this study, one rater examined 20 healthy university students (female = 12, male = 8) in two sessions separated by 7 day intervals. Three stability indexes—the overall stability index (OSI), anterior/posterior stability index (APSI), and medial/lateral stability index (MLSI) in static and dynamic conditions—were measured during single dominant stance. Intraclass correlation coefficient (ICC), standard error measurement (SEM) and 95% confidence interval (95% CI) were calculated. Test-retest ICCs for OSI, APSI, and MLSI were 0.85, 0.78, and 0.84 during static condition and were 0.77, 0.77, and 0.65 during dynamic condition, respectively. We concluded that the postural stability assessment using Biodex stability system demonstrates good-to-excellent test-retest reliability over a 1 week time interval.

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Pedro Paulo Deprá, Avelino Amado and Richard E.A. van Emmerik

, the participant was instructed to accurately track the moving target with the head-mounted laser pointer. Each target condition was performed under a unipedal (preferred leg) and bipedal standing posture in a randomized order. For each postural condition, there were four blocked trials taking 60 s

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Victor Spiandor Beretta, Fabio Augusto Barbieri, Diego Orcioli-Silva, Paulo Cezar Rocha dos Santos, Lucas Simieli, Rodrigo Vitório and Lilian Teresa Bucken Gobbi

predictor of falls in people with PD, principally during challenging postural tasks (unipedal and tandem adapted standing). Materials and Methods Participants In total, 28 people with PD (18 men) were selected from a specialized PD center in São Paulo, Brazil, to participate in this study (Table  1 ). The

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Gemma V. Espí-López, Pilar Serra-Añó, David Cobo-Pascual, Manuel Zarzoso, Luis Suso-Martí, Ferran Cuenca-Martínez and Marta Inglés

distance (in centimeters) was recorded on the data collection sheet. The average of the 3 repetitions was used for subsequent analysis. This test has shown an excellent intrarater reliability (intraclass correlation coefficient = .85–.91). 22 Static Balance Static balance was assessed by the unipedal

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Kyung-Min Kim, Christopher D. Ingersoll and Jay Hertel

Context:

Focal ankle-joint cooling (FAJC) has been shown to increase Hoffmann (H) reflex amplitudes of select leg muscles while subjects lie prone, but it is unknown whether the neurophysiological cooling effects persist in standing.

Objective:

To assess the effects of FAJC on H-reflexes of the soleus and fibularis longus during 3 body positions (prone, bipedal, and unipedal stances) in individuals with and without chronic ankle instability (CAI).

Design:

Crossover.

Setting:

Laboratory.

Participants:

15 young adults with CAI (9 male, 6 female) and 15 healthy controls.

Intervention:

All subjects received both FAJC and sham treatments on separate days in a randomized order. FAJC was accomplished by applying a 1.5-L plastic bag filled with crushed ice to the ankle for 20 min. Sham treatment involved room-temperature candy corn.

Main Outcome Measures:

Maximum amplitudes of H-reflexes and motor (M) waves were recorded while subjects lay prone and then stood in quiet bipedal and unipedal stances before and immediately after each treatment. Primary outcome measures were Hmax:Mmax ratios for the soleus and fibularis longus. Three-factor (group × treatment condition × time) repeated-measures ANOVAs and Fisher LSD tests were performed for statistical analyses.

Results:

Significant interactions of treatment condition by time for prone Hmax:Mmax ratios were found in the soleus (P = .001) and fibularis longus (P = .003). In both muscles, prone Hmax:Mmax ratios moderately increased after FAJC but not after sham treatment. The CAI and healthy groups responded similarly to FAJC. In contrast, there were no significant interactions or main effects in the bipedal and unipedal stances in either muscle (P > .05).

Conclusions:

FAJC moderately increased H-reflex amplitudes of the soleus and fibularis longus while subjects were prone but not during bipedal or unipedal standing. These results were not different between groups with and without CAI.

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Kyung-Min Kim, Joo-Sung Kim and Dustin R. Grooms

Context: Patients with somatosensory deficits have been found to rely more on visual feedback for postural control. However, current balance tests may be limited in identifying increased visual dependence (sensory reweighting to the visual system), as options are typically limited to eyes open or closed conditions with no progressions between. Objective: To assess the capability of stroboscopic glasses to induce sensory reweighting of visual input during single-leg balance. Design:Descriptive Setting: Laboratory Participants: 18 healthy subjects without vision or balance disorders or lower extremity injury history (9 females; age = 22.1 ± 2.1 y; height = 169.8 ± 8.5 cm; mass = 66.5 ± 10.6 kg) participated. Interventions: Subjects performed 3 trials of unipedal stance for 10 s with eyes open (EO) and closed (EC), and with stroboscopic vision (SV) that was completed with specialized eyewear that intermittently cycled between opaque and transparent for 100 ms at a time. Balance tasks were performed on firm and foam surfaces, with the order randomized. Main Outcome Measures: Ten center-of-pressure parameters were computed. Results: Separate ANOVAs with repeated measures found significant differences between the 3 visual conditions on both firm (P-values =< .001) and foam (P-values =< .001 to .005) surfaces for all measures. For trials on firm surface, almost all measures showed that balance with SV was significantly impaired relative to EO, but less impaired than EC. On the foam surface, almost all postural stability measures demonstrated significant impairments with SV compared with EO, but the impairment with SV was similar to EC. Conclusions:SV impairment of single-leg balance was large on the firm surface, but not to the same degree as EC. However, the foam surface disruption to somatosensory processing and sensory reweighting to vision lead to greater disruptive effects of SV to the same level as EC. This indicates that when the somatosensory system is perturbed even a moderate decrease in visual feedback (SV) may induce an EC level impairment to postural control during single-leg stance.

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Original Research Movement Variability and Muscle Activity Relative to Center of Pressure during Unipedal Stance on Solid and Compliant Surfaces James L. Croft * Vinzenz von Tscharner * Ronald F. Zernicke * 10 2008 12 4 283 295 10.1123/mcj.12.4.283 Effects of Object Size on Intralimb and

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23 1 52 62 10.1123/jab.23.1.52 Analysis of Center-of-Pressure Data during Unipedal and Bipedal Standing Using Fractional Brownian Motion Modeling Cyril Burdet * Patrice Rougier * 2 2007 23 1 63 69 10.1123/jab.23.1.63 Measurements of Wrist and Finger Postures: A Comparison of Goniometric and