Movement segmentation and visual perturbation increase developmental differences in motor control and learning

We examined the developmental differences in motor control and learning of a two‐segment movement. One hundred and five participants (53 female) were divided into three age groups (7–8 years, 9–10 years and 19–27 years). They performed a two‐segment movement task in four conditions (full vision, fully disturbed vision, disturbed vision in the first movement segment and disturbed vision in the second movement segment). The results for movement accuracy and overall movement time show that children, especially younger children, are more susceptible to visual perturbations than adults. The adults’ movement time in one of the movement segments could be increased by disturbing the vision of the other movement segment. The children's movement time for the second movement segment increased when their vision of the first movement segment was disturbed. Disturbing the vision of the first movement segment decreased the percentage of central control of the second movement in younger children, but not in the other two age groups. The children's normalized jerk was more easily increased by visual perturbations. The children showed greater improvement after practice in the conditions of partial vision disturbance. As the participants’ age increased, practice tended to improve their feedforward motor control rather than their feedback motor control. These results suggest that children's central movement control improves with age and practice. We discuss the theoretical implications and practical significance of the differential effects of visual perturbation and movement segmentation upon motor control and learning from a developmental viewpoint.     

认知任务对直立姿势的视觉控制的影响

为揭示认知任务对直立姿势的视觉控制的影响, 本研究采用双重任务的方法, 要求18名健康的成年被试在4种条件(2认知条件×2视觉条件)下尽力保持直立姿势的稳定。姿势动摇的测量采用头顶拍摄的方法并计算误差均方根、平均速度以及Romberg商数。研究结果显示认知任务和视觉条件之间的交互作用显著, 而且当有认知任务时姿势动摇的Romberg商数显著降低。这些结果说明认知任务抑制了直立姿势控制过程中的视觉加工。     

The Effects of Relaxation and Postural Training on External Perception: Improvement of Visual Acuity, Visual Field, and Hearing Acuity

This study examined the effects of muscular relaxation and postural training on external perception using a visual acuity test, a visual field test, and a hearing acuity test. Eighteen undergraduate students were randomly assigned to experimental and control groups. The experimental group underwent muscular relaxation and postural training. Each subject in this group was administered the tests before and after the training. Each subject in the control group carried out the tests before and after participating in a 30-min conversation with the experimenter. On all three tests, the experimental group improved significantly more than the control group.     

The Impact of Segmental Trunk Support on Posture and Reaching While Sitting in Healthy Adults

The authors investigated postural and arm control in seated reaches while providing trunk support at midribs and pelvic levels in adults. Kinematics and electromyography of the arm and ipsiliateral and contralateral paraspinal muscles were examined before and during reaching. Kinematics remained constant across conditions, but changes were observed in neuromuscular control. With midribs support, the ipsilateral cervical muscle showed either increased anticipatory activity or earlier compensatory muscle responses, suggesting its major role in head stabilization. The baseline activity of bilateral lumbar muscles was enhanced with midribs support, whereas with pelvic support, the activation frequency of paraspinal muscles increased during reaching. The results suggest that segmental trunk support in healthy adults modulates ipsilateral or contralateral paraspinal activity while overall kinematic outputs remain invariant.     

Human Energy Expenditure and Postural Coordination on the Mechanical Horse

The authors investigated and compared the energy expenditure and postural coordination of two groups of healthy subjects on a mechanical horse at 4 increasing oscillation frequencies. Energy expenditure was assessed from the oxygen consumption, respiratory quotient, and heart rate values, and postural coordination was characterized by relative phase computations between subjects (elbow, head, trunk) and horse. The results showed that the postural coordination of the riders was better adapted (i.e., maintenance of in-phase and antiphase) than that of the nonriders, but the energy expenditure remains the same. Likewise, we observed an energy system shifting only for nonriders (from aerobic to lactic anaerobic mode). Finally, cross-correlations showed a link between energy expenditure and postural coordination in the riders (i.e., effectiveness).     

The impact of a child bike seat and trailer on the objective overtaking behaviour of motorized vehicles passing cyclists

IntroductionThe lateral clearance distance of a motorized vehicle while overtaking a cyclist is a key indicator of safety. This lateral clearance distance has never been measured for cyclists transporting a child. Therefore the aim of this study was to investigate the behaviour of motorized vehicles in overtaking cyclists with and without a child on the same bicycle.MethodsThe lateral clearance distance of the overtaking manoeuvres of motorized vehicles was measured using an instrumented bicycle when performing 19 cycling trips on one single road with two different types of cycling infrastructure (a bike lane and shared lane marking) in the Brussels Capital Region (Belgium). Mixed effect regression was used to examine the effect of cycling condition (cyclist without a child [control], cyclist with a child bike seat and cyclist with a child bike trailer) and secondary independent variables (i.e. cycling infrastructure, peak traffic hours and traffic density) on the lateral clearance distance.ResultsThe mean lateral clearance distance in ‘cyclists without child’ was significantly smaller (117.3 cm) than in ‘cyclists with child’ (128.8 cm) (95%CI [7.2;15.9]). Looking at ‘morning peak traffic hours’ (i.e. 7:00 to 9:00 a.m.) a cyclist with child bike seat was overtaken at greater lateral clearance distances than a cyclist with a child bike trailer or a cyclist without child (p=0.041). Furthermore, the percentage of passing manoeuvres under 100 cm was significantly higher in ‘cyclist without child’ (35.3%) in comparison to ‘cyclist with child bike seat’ (21.8%) and ‘cyclist with child bike trailer’ (21.8%) (Chi2=29.19, p<0.001). No significant differences were found between a shared lane marking and bike lane.ConclusionDrivers of motorized vehicles do adapt their overtaking manoeuvre when they overtake cyclists transporting a child, keeping greater and therefore safer lateral clearance distances. In morning peak traffic hours and/or crowded circumstances the child bike seat can be considered as the safest way to transport a child in terms of lateral clearance distance. In general, with 25.3% overtaking manoeuvres under 100cm, police should monitor compliance with the traffic rules with regard to cyclists, and motorists should be more aware of the overtaking traffic rules.     

Effects of A Dual-Task Intervention in Postural Control and Cognitive Performance in Adolescents

Abstract

The aim was to assess dual- versus single-task training for motor performance and cognitive performance in adolescents. Two experiments were performed. In the first, 30 adolescents were randomized to three groups to determine the effect of dual-task difficulty on postural control: α-scaling and root mean square (RMS). In the second, 20 adolescents were randomized to two groups to determine the effect of dual-task practice to improve working memory. RMS in the post-test was lower than the pre-test in both dual-task groups, while α-scaling was lower in post-test than pre-test only in the high-difficulty dual-task group. A practice effect was observed on the percentage of correct answers only in the dual-task group (p?=?0.035). Thus, dual-task training could enhance motor and cognitive performance more than single-task training.     

Attention focus and self-touch in toddlers: The moderating effect of attachment security

The superior self-regulation and attention-regulation abilities of securely attached children have been repeatedly demonstrated. However, the mechanisms that allow securely attached children to exhibit higher levels of attention focus than insecurely attached (anxious-ambivalent and anxious-avoidant) children need to be explored. One possible mechanism that has been hypothesized to play a role in focusing attention is self-touch. Previous research has shown that 10-year-old children exhibit more bilateral self-touch (i.e., both hands are simultaneously moving onto each other or on the body, and both hands are in contact with each other or with the body), but not lateral self-touch (i.e., one hand is moving on the other hand or on the body, and the hand is in contact with the other hand or with the body), when they focus attention on a task. Because bilateral coordination is still developing during childhood, we expected that lateral self-touch, instead of bilateral self-touch, may be associated with attention focus for toddlers. The objectives of the present study were to examine whether securely attached toddlers exhibit more self-touch, particularly lateral self-touch, while they focus on a task than while they do not focus on a task. We expected to find that the association between lateral self-touch and attention focus is not as strong for insecurely attached toddlers. Data from forty-nine mother-child dyads were employed for analyses. The attachment classification of the children was determined using the Strange Situation. The duration of attention focus and self-touch behavior during a reading task were coded. An association between lateral self-touch and attention focus was found for children of all attachment classifications. This association was particularly strong for securely attached children. We discuss the possibility that securely attached toddlers may use lateral self-touch to regulate attention.     

Effects of Visual Manipulation in Sit-to-Stand Movement in Children With Cerebral Palsy

The authors sought to verify the effects of vision on sit-to-stand (STS) movement performance by means of postural sway in children with cerebral palsy (CP) and typical children (TC). Participants were 42 TC and 21 children with CP. STS movement was assessed with eyes open and with eyes closed. Area and velocity of center of pressure sway were analyzed in each of the 3 STS phases. We observed greater postural sway during STS movement with eyes closed. Children with CP presented greater postural sway than TC did. Both groups exhibited greater postural instability with absence of vision expressing the role of vision to keep postural stability. Moreover, the greater postural instability was observed in children with CP.