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P.R. Rougier, S. Berger, S. Barral and O. Rachet

To assess the postural strategies developed over the first 2 months following surgery by ACL patients during rehabilitation and highlight the sensory-motor impairment recovery, 21 patients were measured at three timeframes. Three two-legged standing conditions were assessed: with the eyes open, with the eyes closed either wearing or not wearing a knee orthosis. The results indicate that the weight-bearing asymmetry, initially observed (i.e., 56–44% of body-weight), disappeared progressively during rehabilitation (51–49%). The comparison of the plantar center-of-pressure displacements under both sound and operated legs demonstrated noticeable differences that also tended to decrease but without reaching a matched behavior during the last measures. These effects were seen in both eyes open and eyes closed conditions with the greatest effects in the latter condition. Wearing a knee orthosis inferred no particular changes in the postural control behaviors. These data could be used as benchmarks for highlighting the effects on undisturbed postural control of various surgery techniques and/or rehabilitation protocols.

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Sébastien Viel, Marianne Vaugoyeau and Christine Assaiante

In the current study, we adopted the hypothesis that the body scheme disturbances occurring during adolescence might lead subjects to transiently neglect proprioceptive information and that adolescents might rely more strongly on vision to control their orientation and stabilize their body. To check this point, we asked adolescents 14–15 years to maintain vertical stance while very slow sinusoidal oscillations in the frontal plane were applied to the supporting platform at 0.01 Hz (below the detection threshold of the semicircular canal system) and at 0.06 Hz (above) with the eyes open and closed. Two postural components, orientation and segmental stabilization, were analyzed at the head, shoulder, trunk, and pelvis levels. At the lowest frequency without vision, the performances of adolescents were much less efficient than those of adults. Moreover, this study showed that vision plays a predominant role in adolescents’ control of orientation and body stabilization. At 0.06 Hz without vision, a clearcut difference was observed between the strategies used by girls and boys; specifically, the maturation of the segmental stabilization processes was found to be more advanced in girls than in boys. However, no such difference was observed at 0.01 Hz. Lastly, comparisons between the data obtained in adolescents and those previously obtained in young adults (Vaugoyeau, Viel, Amblard, Azulay, & Assaiante, 2008) clearly show that adolescents use different postural strategies and that they are not yet capable of reaching comparable postural performance levels to those observed in adults. Because adolescents were not able to use the proprioceptive information available to improve their postural control, we concluded that they showed a maturational lag in comparison with adults. This suggests that the mechanisms underlying postural control are still maturing during adolescence, which might constitute a transient period of proprioceptive neglect in sensory integration of postural control.

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Sean Clark, Peter W. Iltis, Crystal J. Anthony and Andrea Toews

Despite widespread use of the functional-reach (FR) and limits-of-stability (LOS) tests, comparisons of postural strategies and postural limits for these tests have not been previously reported. The purpose of this study was to compare postural strategies as determined by cross-correlation analyses of trunk and lower leg angular displacements and postural limits as assessed by maximum center-of-gravity (COG) excursions as older adults at low fall risk completed the FR and LOS tests. Fourteen older adults completed three FR and LOS trials while standing on a Balance Master® force platform. Results indicated that despite relatively similar instructions to reach or lean as far as possible without losing balance or altering the base of support, their performance differed with regard to postural strategies employed and maximum COG excursions produced. These findings suggest that because of differences in task constraints, FR and LOS tests should not be used interchangeably.

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Patrice Rougier, Dalila Belaid, Sylvie Cantalloube, Delphine Lamotte and Jacques Deschamps

To assess the postural strategies developed by patients after total hip arthroplasty (THA), 14 patients were measured 12 days after surgery. The respective role played by both sound and prosthetic legs and the compensatory mechanisms were assessed through a separate measure of the center-of-pressure (CP) trajectories under each foot. The movements of the center-of-gravity (CG) were estimated from those of the resultant CP to determine postural performance. The postural behavior was compared with those of a group of age-matched healthy subjects required to adopt a slightly asymmetrical weight distribution. Patient results indicate greater movements for both plantar and resultant CP displacements, principally along the antero-posterior (AP) axis, a decreased contribution of the hip mechanisms in the production of CP displacements along the medio-lateral (ML) axis, greater resultant CP and CG movements along the AP axis and increased differences between CP and CG along both ML and AP axes. The postural specificity of the THA patients appears to be due to a global sensorimotor impairment that alters the control of the loading-unloading mechanism at the hip level.

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Patrice R. Rougier and Samir Boudrahem

Past studies have emphasized the beneficial effect of additional visual feedback (VFB) on the capacity of healthy adults to decrease the amplitudes of the center-of-pressure minus center-of-gravity (CP-CGv) movements. To better assess these capacities, 56 subjects were asked to stand still on a force platform and to use the visual information provided. Dependency coefficients, based on their capacity to lower their CP-CGv movements and therefore relax their lower limb muscles, as well as parameters aimed at characterizing their postural strategies were measured across VFB conditions including (1) CP displacements in real time (VFBCP0), (2) CP displacements with a 600-ms delay (VFBCP600), and (3) CP-CGv displacements with a 600-ms delay (VFBCP-CG600). A non-VFB condition (eyes open) was also included. Several linear correlations were used to specify the relation between subjects’ capacity to relax, compared with the VFBCP0 condition, across the three remaining conditions. The data highlight the complementary nature of the VFB conditions and establish the postural control behaviors necessary to use these VFB protocols efficiently.

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Rodolfo B. Parreira, Marcela C. Boer, Lucas Rabello, Viviane de Souza P. Costa, Eros de Oliveira Jr. and Rubens A. da Silva

The aim of this study was to evaluate the changes in center of pressure (COP) movement in four time intervals (5, 10, 15 and 30 s) during a one-leg stance test performed by young and elderly adults. Twelve young adults (mean 20 years) and 12 elderly subjects (mean 68 years) participated in this study. The subjects performed three 30 s trials of an eyes open one-leg stance test on a force platform, in which the COP parameter was computed at four points in time from same original COP signal. Significant differences were found between the young and elderly adults (P < .007) only at the 10, 15 and 30 s intervals. For both groups, COP changes were significantly different between the 5 s time interval and other intervals (10, 15 and 30 s). In conclusion, these results pointed out that age-related difference in COP changes were time dependent. This suggests that the use of longer durations increases the possibility of distinguishing more subtle differences in postural strategy among different groups of subjects.

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Xavier García-Massó, Adrià Marco-Ahulló, Israel Villarrasa-Sapiña, Julio Álvarez-Pitti and Jose-Luis Bermejo

; McGraw, McClenaghan, Williams, Dickerson, & Ward, 2000 ; Menegoni et al., 2009 ; Mignardot, Olivier, Promayon, & Nougier, 2010 ; Villarrasa-Sapiña et al., 2016 ). During childhood, the development of the central nervous system and the acquisition of new postural strategies improve postural stability

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Alberto Pardo-Ibáñez, Jose L. Bermejo, Sergio Gandia, Julien Maitre, Israel Villarrasa-Sapiña, Isaac Estevan and Xavier Garcia-Masso

joints are highly and positively correlated with stability ( Onambele, Narici, & Maganaris, 2006 ). Second, another explanation could be linked to the changes in the postural strategies of older adolescents, as they may have changed their strategy to use a more efficient one than younger participants

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Daniel Hamacher, Dennis Hamacher, Roy Müller, Lutz Schega and Astrid Zech

) decreasing fall risk. At the same time, the mean height of MTC decreased, which in turn would increase the risk of stumbling. This means that our results indicate that when researchers aim to classify participants into one of the two posture strategies, different motor parameters can lead to different

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Isaac Estevan, Sergio Gandia, Israel Villarrasa-Sapiña, José Luis Bermejo and Xavier García-Massó

but require a minimum amount of attention not only in children but also in adolescents/young adults ( Palluel, Nougier, & Olivier, 2010 ; Remaud, Boyas, Caron, & Bilodeau, 2012 ). During childhood, the development of the central nervous system and the acquisition of new postural strategies improve