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Thomas A. Stoffregen

It is widely assumed that healthy aging includes a decline in the stability of standing body sway. Certainly, the spatial magnitude of postural sway increases with age. However, the interpretation of this effect as a decline in the ability to stabilize posture rests, in part, on assumptions about the nature and definition of stability in stance. In this article, I review data on the control of standing posture in healthy older adults. I focus on a growing list of studies that demonstrate the retention, among healthy older adults, of the ability functionally to modulate postural sway in support of “suprapostural” activities. I address laboratory research, but also field studies carried out in a setting that dramatically challenges the control of stance: life on ships at sea. I argue that it may be possible, and certainly will be useful, to address directly the functional control of stance in older adults.

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Fawaz A. Alwadani, Huaqing Liang and Alexander S. Aruin

The central nervous system assimilates afferent sensory inputs from the visual, proprioceptive, and vestibular systems to maintain a stable bipedal stance ( Ivanenko & Gurfinkel, 2018 ; Massion, 1994 ). When standing still, the vertical projection of the center of gravity rests anteriorly to the

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Semyon M. Slobounov and Karl M. Newell

This study provides a comparative analysis of certain features of upright and inverted stance in collegiate-level competitive gymnastic and diving athletes. A particular focus was the compensatory movement strategies used to maintain inverted stance. The analyses revealed that the motion of the center of pressure was significantly greater in the hand stance as opposed to the upright stance condition. Instability increased over the duration of a 15-s hand stance trial, and it was paralleled by the introduction of a small set of compensatory movement strategies that included enhanced motion at the distal segments of the legs and at the elbow joint. The compensatory movement strategies appeared to be in support of minimizing variability of motion in the head and trunk. The relative contribution of the principal sources of this instability in the hand stance remains to be determined.

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Masakazu Matsuoka, Hiroshi Kunimura and Koichi Hiraoka

Humans respond to translation of the support surface under their feet in stance to maintain the center of pressure within the base of support (see Jacobs et al., 2008 ; Jacobs & Horak, 2007 ; Massion, 1994 ). This response is produced by activity of the limb and trunk muscles ( Horak & Nashner

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Marianne J.R. Gittoes and Cassie Wilson

This study aimed to develop insight into the lower extremity joint coupling motions used in the maximal velocity phase of sprint running. Two-dimensional coordinate data were used to derive sagittal plane joint angle profiles of sprint running trials. Intralimb joint coupling motions were examined using a continuous relative phase (CRP) analysis. The knee-ankle (KA) coupling was more out of phase compared with the hip-knee (HK) coupling across the step phase (mean CRP: KA 89.9° HK 34.2°) and produced a lower within-athlete CRP variability (VCRP) in stance. Touchdown (TD) produced more out-of-phase motions and a larger VCRP than toe-off. A destabilization of the lower extremity coordination pattern was considered necessary at TD to allow for the swing-to-stance transition. The key role that the KA joint motion has in the movement patterns used by healthy athletes in the maximal velocity phase of sprint running was highlighted.

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Patrice R. Rougier, Thibaud Coquard, Thierry Paillard, Clément Ankaoua, Jeanne Dury, Corentin Barthod and Dominic Perennou

statistically significant effect was, however, reported for LU and PD mechanisms between these two feet positions ( Rougier, 2008 ). Our objective in that study was to assess to which extent the postural control strategies, previously reported for characterizing upright stance maintenance with WBA on solid

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Stacy E. Stamm and Loren Z.F. Chiu

When the rear- and forefoot are constrained, calcaneal plantar flexion may occur, deforming the longitudinal arch. Previous research has reported calcaneal motion relative to the tibia or forefoot; these joint rotations may not accurately describe rotation of the calcaneus alone. This investigation: (1) characterized the calcaneus and leg segment and ankle joint rotations during stance in gait, and (2) described the range of calcaneal plantar flexion in different structural arch types. Men (n = 14) and women (n = 16) performed gait in a motion analysis laboratory. From heel strike to heel off, the leg rotated forward while the calcaneus plantar flexed. Before foot flat, calcaneal plantar flexion was greater than forward leg rotation, resulting in ankle plantar flexion. After foot flat, forward leg rotation was greater than calcaneal plantar flexion, resulting in ankle dorsiflexion. Structural arch type was classified using the longitudinal arch angle. The range of calcaneal plantar flexion from foot flat to heel off was small in low (−2° to −8°), moderate in high (−3° to −12°), and large in normal (−2° to −20°) structural arches. Calcaneal plantar flexion in gait during midstance may reflect functional arch characteristics, which vary depending on structural arch type.

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Annick Ledebt, Jules Becher, Janneke Kapper, Rianne M. Rozendaal, Rachel Bakker, Iris C. Leenders and Geert J.P. Savelsbergh

The aim of the present study was to examine the effects of balance training with visual feedback on stance and gait in school-age children with hemiplegic cerebral palsy. Ten participants between 5 and 11 years of age were assigned to either the training or the control group according to an aged-stratified randomization. The training corresponded to three sessions per week during six weeks. Stance and gait parameters, based on force plate data, were assessed three times in both groups: (a) at the beginning of the study (before training); (b) after six weeks; (c) after ten weeks. Spatial and temporal parameters were calculated. The results for stance showed that the training improved the performances on the tasks that were trained. More interesting, the results for gait showed that the walking pattern became more symmetrical after the training.

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Molly B. Johnson and Richard E.A. Van Emmerik

Sensory feedback from the vestibular system and neck muscle stretch receptors is critical for the regulation of postural control. The postural relationship of the head to the trunk is a major factor determining the integration of sensory feedback and can be interfered with by varying head orientation. This study assessed how 60-s of standing with the head neutral, flexed, or extended impacted postural stability during upright stance and during forward lean in 13 healthy participants (26 ±5 years old). During both quiet upright stance and maximal forward lean, head extension increased postural center of pressure (COP) velocity and decreased the COP time-to-contact the anterior stability boundary compared with the head neutral condition. Head flexion did not differ from head neutral for either of the stance conditions. This study demonstrates that interfering with the head-trunk relationship by adopting extended, but not flexed, head orientations interferes with postural control that may impact postural stability during both quiet upright stance and maximal forward lean conditions.

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Erik B. Simonsen, Katrine L. Cappelen, Ragnhild í Skorini, Peter K. Larsen, Tine Alkjær and Poul Dyhre-Poulsen

A hip joint flexor moment in the last half of the stance phase during walking has repeatedly been reported. However, the purpose of this moment remains uncertain and it is unknown how it is generated. Nine male subjects were instructed to walk at 4.5 km/h with their upper body in three different positions: normal, inclined and reclined. Net joint moments were calculated about the hip, knee and ankle joint. The peak hip joint flexor moment during late stance was significantly lower during inclined walking than in the two other conditions. During normal walking the iliacus muscle showed no or very weak activity and first at the transition from stance to swing. When walking reclined, a clear but rather low activity level of the iliacus muscle was seen in the first half of the stance phase, which could contribute to the hip moment. In the inclined condition the iliacus showed much increased activity but only in the swing phase. It is concluded that the hip flexor moment in question is largely generated by passive structures in the form of ligaments resisting hip joint extension.