Why We Walk the Way We Do

By using inverse dynamics and forceplate recordings, this study established the principle of oscillating systems and the influence of gravity and body parameters on the programming of the gait parameters, step frequency and length. Calculation of the ratio of the amplitude of the center of mass (CM) and the center of foot pressure (CP) oscillations yielded an equation and established a biomechanical constant, the natural body frequency (NBF). NBF appears to be an absolute invariant parameter, specific to human standing posture and gait in terrestrial gravity, which influences the relative positions of CM and CP and whose value separates the frequency bands of standing posture from those for gait. This equation was tested by using the experimental paradigm of stepping in place and then used in calculating the magnitude of CM oscillations during gait. The biomechanical analysis of the experimental observations allows one to establish the relationships between body parameters and gravity and the central programming of locomotor parameters.     

Influence of Destabilization on the Temporal Characteristics of “Volitional” Stepping

Previous work suggests that there may be fundamental differences between compensatory stepping responses evoked by postural perturbation and visually cued “volitional” stepping (e.g., gait initiation). In contrast to visual cueing, postural destabilization evokes an array of sensory inputs that are intrinsically linked to the mobilization of rapid compensatory responses. The hypothesis examined in this study was that this fundamental difference would lead to distinct changes in the temporal characteristics of the stepping response. Six healthy young adults were instructed to step quickly in response to either visual cueing or anterioposterior platform motion. Both forward and backward stepping responses were characterized, using measures of vertical ground reaction force. A stereotypical temporal patterning of the stepping response occurred in both stimulus conditions and both directions of stepping, and anticipatory postural adjustments were evident in all trials. However, postural destabilization led to a more rapid initiation and execution of the temporal pattern, in comparison with visually cued responses. The most pronounced effect was seen in the duration of the response, which was reduced by a factor of two, with approximately proportional foreshortening of both the preparatory and swing phases. The results suggest that sensory information conveying a state of instability has a distinct influence on the characteristics of a subsequent stepping reaction. The persistence of the anticipatory postural adjustments suggests that the failure to see this element of the response in previous studies may reflect fundamental differences between volitional and unplanned compensatory stepping.     

Immediate and Latent Interlimb Transfer of Gait Stability Adaptation Following Repeated Exposure to Slips

The authors trained 21 participants by using blocked-and-mixed exposure to right-side slips and then caused them to slip unexpectedly on the untrained left side. Authors retested participants with a right slip and a left slip at 1 week, 2 weeks, 1 month, and 4 months. The authors found that preslip stability on the first untrained left slip improved and was significantly greater than that on the first right slip, which probably contributed to the reduction in incidence of falls from ~30% to ~10%. Postslip stability and base of support (BOS) slip velocity were similar to those on the first right slip and much lower than those on the last right slip. Increases in pre- and postslip stabilities and BOS slip velocity during the left slip led to reductions in backward balance loss (BLOB) from ~95% on initial left slip to ~60% and to ~25% on the 1st and 3rd retest sessions, respectively. In contrast, BLOB remained at a constant ~40% level on the right slip of the same retest sessions. The results indicate a partial immediate transfer and a possible latent transfer.     

Comment on “Retention Characteristics of Motor Short-Term Memory Cues”

Marteniuk (1973) used negative results, which may be attributed to a lack of power, to question the adequacy of variable error as a measure of forgetting. He also used these negative results, along with constant error results which were consistent with the Laabs (1971, 1973) model of motor memory, to reject parts of the model related to variable error. Caution is advised when interpreting negative results and interchanging dependent measures.     

Patterns of Human Interlimb Coordination Emerge from the Properties of Non-Linear,Limit Cycle Oscillatory Processes

The present article represents an initial attempt to offer a principled solution to a fundamental problem of movement identified by Bernstein (1967), namely, how the degrees of freedom of the motor system are regulated. Conventional views of movement control focus on motor programs or closed-loop devices and have little or nothing to say on this matter. As an appropriate conceptual framework we offer Iberall and his colleagues’ physical theory of homeokinetics first elaborated for movement by Kugler, Kelso, and Turvey (1980). Homeokinetic theory characterizes biological systems as ensembles of non-linear, limit cycle oscillatory processes coupled and mutually entrained at all levels of organization. Patterns of interlimb coordination may be predicted from the properties of non-linear, limit cycle oscillators. In a set of experiments and formal demonstrations we show that cyclical, two-handed movements maintain fixed amplitude and frequency (a stable limit cycle organization) under the following conditions: (a) when brief and constantly applied load perturbations are imposed on one hand or the other, (b) regardless of the presence or absence of fixed mechanical constraints, and (c) in the face of a range of external driving frequencies from a visual source. In addition, we observe a tight phasic relationship between the hands before and after perturbations (quantified by cross-correlation techniques), a tendency of one limb to entrain the other (mutual entrainment) and that limbs cycling at different frequencies reveal non-arbitrary, sub-harmonic relationships (small integer, subharmonic entrainment). In short, all the above patterns of interlimb coordination fall out of a non-linear oscillatory design. Discussion focuses on the compatibility of these results with past and present neurobiological work, and the theoretical insights into problems of movement offered by homeokinetic physics. Among these are, we think, the beginnings of a principled solution to the degrees of freedom problem, and the tentative claim that coordination and control are emergent consequences of dynamical interactions among non-linear, limit cycle oscillatory processes.     

Creativity,chaos, and self‐renewal in human systems

The research findings from the psychology of creativity are shown to be of considerable relevance to the study of self‐organization and self‐renewal in human systems. The characteristics of the creative person, and the nature of the creative process, particularly as they have been elaborated by Barron, are shown to be remarkably congruent with recent findings and theoretical elaborations by Abraham, Jantsch, Laszlo, Prigogine, and others in the fields of evolutionary and chaos theory. The broader social implications of chaos and evolutionary theories are fleshed out through an understanding of their characteristics in creative human systems.     

Educating Evolutionary Co-Leadership to Embody a Radically New Development Paradigm

The purpose here is to explore why and how to develop an emerging form of integral leadership—called evolutionary co-leadership—that is responsibly dedicated to the co-evolution of life and humanity on Planet Earth. After offering some fresh distinctions about leadership, this article calls for a shift to a radically new development paradigm, and identifies key qualities and practices of evolutionary co-leadership. It then shares some views on the multiplying effects of an integral approach to co-leadership development—in the context of transforming education—and concludes with some avenues to disseminate this emerging leadership form, mainly to deal constructively with what Barbara Marx Hubbard (2001) calls the current “birthing pains” of a new civilization.     

Predicting early emotion knowledge development among children of colour living in historically disinvested neighbourhoods: consideration of child pre-academic abilities,self-regulation,peer relations and parental education

ABSTRACT

Emotion knowledge, the ability to accurately perceive and label emotions, predicts higher quality peer relations, higher social competence, higher academic achievement, and fewer behaviour problems. Less is known, however, about predictors of early development of emotion knowledge. This study examines emotion knowledge development among children attending pre-Kindergarten and Kindergarten programmes in high-poverty urban schools. The study considers child pre-academic abilities, self-regulation, peer relations and parental education as predictors of emotion knowledge development over two years. The sample (n?=?1034) of children living in historically disinvested neighbourhoods was primarily Black (85%) and low-income (～61%). The sample was part of a longitudinal follow-up study of a cluster (school) randomised controlled trial in ten public elementary schools. Children’s emotion knowledge was assessed with a series of tasks three times over a two-year period. At baseline, parents and teachers reported on peer relations, children completed a test of pre-academic abilities, independent observers rated child self-regulation, and parents reported on their educational attainment. Results demonstrate that emotion knowledge increases over time, and pre-academic abilities, self-regulation, peer relations, and parent education independently predict children’s emotion knowledge. This study highlights multiple factors that predict emotion knowledge among primarily Black children living in historically disinvested neighbourhoods.     

Effects of a Peer Engagement Program on Socially Withdrawn Children with a History of Maltreatment

Children with a history of child maltreatment often have limited social interactions with other children and adults. This study examined the effects of a Peer Engagement Program, consisting of peer mentoring and social skills training with positive reinforcement, in three children with low levels of oral and social interaction. A multiple baseline, single-subject research design was used to test whether introduction of the intervention was associated with increased, directly observed oral interaction and engagement in social activities with peers and adults. The Child Behavior Checklist (CBCL) and the Social Skills Rating Scale (SSRS) were administered before and after intervention. All children showed increased levels of oral and social interaction and improved scores on the SSRS and the CBCL.     

Authors' Response to Lutzker's Evaluation

No abstract available for this article.