Locomotor body scheme

The concept of body schema has been introduced and widely discussed in the literature to explain various clinical observations and distortions in the body and space representation. Here we address the role of body schema related information in multi-joint limb motion. The processing of proprioceptive information may differ significantly in static and dynamic conditions since in the latter case the control system may employ specific dynamic rules and constraints. Accordingly, the perception of movement, e.g., estimation of step length and walking distance, may rely on a priori knowledge about intrinsic dynamics of limb segment motion and inherent relationships between gait parameters and body proportions. The findings are discussed in the general framework of space and body movement representation and suggest the existence of a dynamic locomotor body schema used for controlling step length and path estimation.     

Processes of anticipatory postural adjustment and step movement of gait initiation

The purpose of this study was to elucidate whether the anticipatory postural adjustment (APA) and focal step movement of gait initiation are produced as a single process or different processes and whether the APA receives an inhibitory drive from the ongoing stop process of gait initiation. Healthy humans initiated gait in response to a first visual cue that instructed the initial swing leg. In some trials, a switch or stop cue was also provided after the first cue. When the stop cue was provided, participants withheld gait initiation. When the switch cue was provided, participants immediately switched the initial swing leg. In both the stop and switch tasks, the APA in response to the first cue, represented by the S1 period of the displacement of the center of pressure, appeared in more than half of the trials in which the withholding of gait initiation or switching of the initial swing leg was successfully completed. These findings indicate that the APA and focal step movement of gait initiation are produced as a dual process. In trials in which the APA in response to the first cue appeared, the amplitude and duration of the APA were decreased when the participants switched the initial swing leg or withheld gait initiation. This finding indicates that the ongoing stop process of gait initiation produces an inhibitory drive over the APA. The decreases in the amplitude and duration of the APA during the switching of the initial swing leg were similar to those during the withholding of gait initiation; moreover, the decreases during the switching of the initial swing leg were positively correlated with the decreases during the withholding of gait initiation. Thus, the stop processes during switching the initial swing leg and withholding gait initiation likely share a common inhibitory mechanism over the APA.     

CD_4~+ CD_(25)~+调节性T细胞在妊娠与分娩中的作用

近代生殖免疫学研究认为,正常妊娠维持有赖于母胎免疫耐受的形成,耐受一旦失调,就可能妊娠失败,发生如流产,妊娠期高血压疾病,胎膜早破,分娩发动等。近几年来,国内外学者逐渐认识到CD4+CD25+调节性T细胞在妊娠中的重要作用并进行系列研究。本文就目前CD4+CD25+调节性T细胞在妊娠与分娩中的作用作一综述。     

Human walk-to-run transition in the context of the behaviour of complex systems

This study had two main aims: 1) to investigate if the walk-to-run (WR-) transition occurs when the speed of locomotion is kept constant below the WR-transition speed (speed clamp) and the stride rate is increased monotonously using a metronome and 2) to investigate if diversion of attention and awareness from the locomotion process influences the position of the WR-transition in stride rate, stride length, and locomotion speed (SrSlLs) space.Eighteen healthy individuals (13 men and 5 women) were recruited (age: 23.9 ± 1.5 years, height: 1.77 ± 0.10 m and body mass: 77.3 ± 12.8 kg). Stride-by-stride stride rates, stride lengths, locomotion speeds, and duty factors were determined on a treadmill in 4 different tests: 1) reference WR-transition, 2) preferred walking speed, 3) dual-task test including arithmetic calculations and 4) four speed clamp bouts with different initial velocities.Walk-to-run transitions were elicited in all participants in the speed clamp bouts. When the stride rate ramp was clamped at preferred walking speed the WR-transition stride rate was not significantly different from the WR-transition stride rate during the reference test (t = 2.2, p = 0.312). However, in the SrSlLs space the speed clamp WR-transitions all deviated from the position of the reference WR-transition. Additionally, it was demonstrated that intensive attentional diversion using a dual-task paradigm had very little influence on the position of the WR-transition in the SrSlLs space.It is argued that these observations can be explained in the context of the behavior of complex systems.     

Walking breaks can reduce prolonged standing induced low back pain

Standing is commonly recommended to reduce sedentary behavior in the workplace; however, constrained prolonged standing has also been linked to musculoskeletal symptoms, such as low back pain (LBP). Light physical activity breaks, such as walking, may change lumbar spine posture enough to reduce LBP during standing. This study assessed the effectiveness of inserting 5-minute walking breaks every 25 min for reducing prolonged standing-induced LBP development. Nineteen participants completed two bouts of standing lasting 2 h – one with a 5-minute walking break every 25 min and one with no breaks. Pain measures were completed throughout the trial to categorize participants as pain developers (PDs) or non-pain developers (non-PDs). Lumbar region kinematics angle and range of motion were measured continuously. In standing, 58% (11/19) of participants were PDs, compared to just 26% when walking breaks were inserted. Seventy-three percent (8/11) were categorized as non-PDs with walking breaks. Median lumbar flexion increased during walking compared to standing. Lumbar region range of motion in the coronal and transverse planes also increased during walking. The intermittent lumbar flexion may help decrease LBP during prolonged standing. These results demonstrate that walking breaks may help promote lumbar movement and reduce prolonged standing-induced LBP.     

The Relation Between Childhood Proactive and Reactive Aggression and Substance Use Initiation

The current study examined whether proactive and reactive aggression were associated with the risk for initiation of substance use from fourth to ninth grade in a sample of 126 aggressive children (66% male). In addition, the study examined whether these functions of aggression increased risk for initiation via peer delinquency and peer rejection. Proactive aggression was marginally significantly directly associated with risk for initiation of alcohol use and indirectly associated with risk for initiation of marijuana and tobacco use through peer delinquency. Reactive aggression was associated with increased risk for initiation of tobacco and marijuana use through a complex chain that included both peer rejection and peer delinquency. However, high levels of reactive aggression that did not lead to peer rejection were negatively associated with risk for initiation of tobacco and marijuana use. Implications for intervention are discussed.

The intergenerational transmission of implicit and explicit attitudes toward smoking: Predicting adolescent smoking initiation

This study examined the intergenerational transmission of implicit and explicit attitudes toward smoking, as well as the role of these attitudes in adolescents’ smoking initiation. There was evidence of intergenerational transmission of implicit attitudes. Mothers who had more positive implicit attitudes had children with more positive implicit attitudes. In turn, these positive implicit attitudes of adolescents predicted their smoking initiation 18-months later. Moreover, these effects were obtained above and beyond the effects of explicit attitudes. These findings provide the first evidence that the intergenerational transmission of implicit cognition may play a role in the intergenerational transmission of an addictive behavior.     

DEFINING CHILD NONCOMPLIANCE: AN EXAMINATION OF TEMPORAL PARAMETERS

This study examined compliance parameters for 53 clinic-referred and nonreferred children, ages 2 to 10 years. Although there were significant differences between the referred and nonreferred samples for percentage compliance, there were no significant differences between the referred and nonreferred samples in terms of initiation or completion latencies. The average initiation latency was 5.92 s, whereas 98% of the sample initiated compliance within 14 s. Younger children did take longer to complete tasks. Results suggest that the use of short latencies in defining noncompliance may represent overly conservative criteria.     

A biomechanical analysis of the 'high guard' position of arms during walking in toddlers

In this study, we investigated biomechanical contributions of the high guard position of the arms observed only in a subgroup of toddlers at very early stages of gait development. Six healthy toddlers who showed this peculiar arm posture were involved in this study. They participated in two data collection sessions (1 month apart). We used three-dimensional analysis of arm posture during gait to estimate the changes in forces and torques generated by the arms and acting on the upper trunk segment. Across visits, toddlers’ increase in walking speeds coincided with lowering arm postures. Despite the apparent trend of changes in arm posture in this group of toddlers, the interaction between arm posture and upper trunk position created a variety of changes in forces and torques among individuals. Findings of this study exhibited an example of the exploration of dynamics by toddlers in the early stage of gait development.