The effects of mid-flight whole-body and trunk rotation on landing mechanics: implications for anterior cruciate ligament injuries

ABSTRACT

The purpose was to quantify the effects of mid-flight whole-body and trunk rotation on knee mechanics in a double-leg landing. Eighteen male and 20 female participants completed a jump-landing-jump task in five conditions: no rotation, testing leg ipsilateral or contralateral (WBRC) to the whole-body rotation direction, and testing leg ipsilateral (TRI) or contralateral to the trunk rotation direction. The WBRC and TRI conditions demonstrated decreased knee flexion and increased knee abduction angles at initial contact (2.6 > Cohen’s dz > 0.3) and increased peak vertical ground reaction forces and knee adduction moments during the 100 ms after landing (1.7 > Cohen’s dz > 0.3). The TRI condition also showed the greatest knee internal rotation angles at initial contact and peak knee abduction and internal rotation angles and peak knee extension moments during the 100 ms after landing (2.0 > Cohen’s dz > 0.5). Whole-body rotation increased contralateral knee loading because of its primary role in decelerating medial-lateral velocities. Trunk rotation resulted in the greatest knee loading for the ipsilateral knee due to weight shifting and mechanical coupling between the trunk and lower extremities. These findings may help understand altered trunk motion in anterior cruciate ligament injuries.     

Classroom justice: Perceptions of fairness as a predictor of student motivation,learning, and aggression

The present study examined the relationship between students’ perceptions of distributive and procedural justice in a college course and student motivation concerning the course, affective learning in the course, and aggression toward the course instructor. Although student perceptions of both distributive and procedural justice were positively correlated with student motivation and affective learning and negatively correlated with student aggression toward the course instructor, multiple regression analyses indicated that only perceptions of procedural justice predicted the three criterion variables at a statistically significant level while distributive justice perceptions did not. Implications and suggestions for future research in classroom justice are offered.     

New Counselor Educators’ Scholarly Productivity: Supportive and Discouraging Environments

Eighteen new counselor educators shared in‐depth reports of their efforts to establish an early record of scholarly productivity, critical to their success in academe. Analyses of their experiences using consensual qualitative research methods revealed components of both highly positive and highly discouraging program environments and their impact on participants’ research goals.     

Differential reactions to assertive and communicative acts of toddler boys and girls

34 children were observed in infant play groups. 2 sets of infant behaviors were coded: assertive acts and attempts to communicate with adults. No sex differences were observed at 13 to 14 months in any of these behaviors. However, adults attended to girls' assertive behaviors far less of the time than to boys' assertive behaviors. They attended more to girls' less intense communication attempts and to boys' more intense attempts. When 29 of the same children were observed in toddler play groups no more than 11 months later, there were sex differences in behavior. Boys were more assertive; girls talked to teachers more. Teachers no longer differentiated their responses to boys and girls. Peers reacted more to boys' assertive behavior than to girls.' We hypothesized that caregivers may use stereotypes to guide their reactions to infants because infant behavior is ambiguous. For the toddlers, behavior had become more defined, and caregivers reacted to the behaviors. By using the sex stereotype to guide their reactions to younger children, the caregivers may have perpetuated the stereotype.     

Solving Bernstein's Problem: A Proposal for the Development of Coordinated Movement by Selection

In recent years, many established concepts in the theory of human motor development have undergone profound change, and our knowledge has increased greatly. Nevertheless, some outstanding problems remain unsolved. A central problem concerns the redundancy of effective movements, first pointed out by N. A. Bernstein. The human motor system is mechanically complex and can make use of large number of degrees of freedom. The controlled operation of such a system requires a reduction of mechanical redundancy, effectively by reducing the number of degrees of freedom. More recent work has shown that this problem is hard to solve explicitly by computing solutions to the equations of motion of the system. Equally challenging to traditional computational approaches is the fact the motor systems show remarkable adaptability and flexibility in the presence of changing biomechanical properties of motor organs during development and when faced with different environmental conditions or tasks. Solutions to these problems would have a large impact on a variety of issues in child development. In this article, we stress the importance of the somatic selection of neuronal groups in maps for the progressive transformation of a primary movement repertoire into a set of motor synergies and adaptive action patterns. We present results from computer simulations of a simple motor system that works according to such selectional principles. This approach suggests a provisional solution to Bernstein's problem and provides new parameters to guide experimental approaches to the development of sensorimotor coordination.     

Quantifying Qualitative Scholarship: A Fool’s Errand or a Methodological Necessity?

This paper describes our efforts to systematically generate knowledge from ethnographic and other qualitative scholarship as a way of bridging intellectual gaps found in quantitative research. We ground this scholarly endeavor in the study of gangs, which has a lengthy history in the field of criminology, yet lacks a coherent, coordinated, and comparative understanding of gang dynamics, behavior, and impacts. We discuss the importance of acknowledging the multiple and mixed methodologies used in gang scholarship and detail the inductive, deductive, and iterative process that helped us (1) develop a comprehensive coding instrument for coding a range of qualitative works, (2) establish the instrument’s inter-rater reliability, and (3) remain cognizant and reflexive about the strengths of both quantitative and qualitative research. Finally, we share the critical yet informative challenges we faced throughout the project and conclude with reflections on why the project was unsuccessful in the way we originally envisioned.     

What’s in a name: dimensions of social learning in teacher groups

Induced by a literature review, this paper presents a framework of dimensions and indicators highlighting the underpinning aspects and values of social learning within teacher groups. Notions of social networks, communities of practice and learning teams were taken as the main perspectives to influence this social learning framework. The review exercise resulted in four dimensions: (1) practice, (2) domain and value creation, (3) collective identity and (4) organization. The indicators corresponding to these dimensions serve as the foundation for understanding social learning in practice. The framework of dimensions and indicators can be of assistance for researchers as well as teacher groups that aim to assess their views on social learning and analyse whether these views fit the learning goals of the group or that adjustments are required. In this way, learning processes within groups of teachers can be improved.     

Exploring Trajectories of Young Mothers’ Parenting Stress in Early Childhood: Associations with Protective Factors and Psychological Vulnerabilities

SYNOPSIS

Objective . Most parents manage some degree of parenting stress without serious concerns, but young mothers experience parenting stress at higher levels than adult mothers; high parenting stress is problematic due to its association with children’s socioemotional and behavior problems and the increased likelihood of maltreatment. Understanding the circumstances that precipitate or mitigate parents’ stress can have lasting impacts for child well-being. Extant research fails to account for both longitudinal and individual variation in young mothers’ parenting stress, leading to equivocal findings about the nature of mothers’ parenting stress trajectories across early childhood. Design . The present study used growth mixture modeling (GMM) to model the trajectories of 544 first-time young mothers’ parenting stress from children’s infancy to school-age. We considered how protective factors (i.e., social support) and psychological vulnerabilities (i.e., depression) experienced during the transition to parenthood were associated with parenting stress trajectories and variation within trajectories when children were of school-age. Results . GMM identified three trajectories of parenting stress: “low stable”, “high increasing”, and “high decreasing.” Protective factors were related to low and decreasing patterns of parenting stress, whereas psychological vulnerabilities were associated with higher parenting stress patterns. Conclusions . This study has implications for programs and services that help young mothers cope with the demands of parenting and reduce parenting stress.