Perception-action coupling in children with and without DCD: Frequency locking between task-relevant auditory signals and motor responses in a dual-motor task.

BACKGROUND: The current research examines the relationship between perceptual and motor processes, known as perception-action or sensorimotor coupling, and the potential differences in perception-action coupling among children with and without Developmental Coordination Disorder (DCD) and adults in a gross-motor co-ordination task (clapping while marching) when a task-relevant driving sensory signal is present. METHODS: Ten children with DCD (7.32 + 0.23 years), eight typically developing (TD) children who were age-, gender- and racially/ethnically matched (6.91 + 0.24 years) and 10 college-aged adults were participants in this study. Participants clapped and marched to an auditory beat at four different frequencies: 0.8, 1.2,1.6 and 2.0 Hz. The relative timing measures of mean relative phase (MRP) and variability of relative phase (VRP) were calculated and compared using 3 (group) x 4 (frequency) x 2 (limb) anovas. Qualitatively, participants were assessed for the presence of absolute coupling (100% + 15% MRP). RESULTS: Statistically significant differences in MRP occurred for coupling, frequency and group, and post hoc analysis indicated that the adult group differed from both the DCD and TD groups, who did not differ from each other. In VRP, there were significant main effects for coupling and group, and a significant interaction between group and frequency, with post hoc analysis indicating the DCD group to be different from the TD and adult groups. Qualitatively, both the adult and TD groups increased in the number of participants who adopt absolute coupling as frequency increases. In contrast, the DCD participants adopt this absolute coupling far less frequently overall; in fact, the number of participants adopting this pattern decreases as frequency increases. CONCLUSIONS: These results indicate that children with DCD have difficulties with both the co-ordination and the control of their perception-action coupling for this particular task.

Individual differences and similarities in the stability, timing consistency, and natural frequency of rhythmic coordinated actions.

Under preferred speed conditions, 15 adults undertook bimanual in-phase and antiphase tapping, clapping, galloping, galloping while clapping, and crawling on their hands and feet. We measured stability of interlimb coordination (standard deviation of mean interlimb relative phasing), single limb timing consistency (coefficient of variation of mean single limb cycle durations), and natural limb frequency. Pearson product-moment correlations among tasks established that only the natural limb frequencies were significantly correlated (specifically among gross motor actions in which larger contributions of inertial loads contribute to natural frequencies). Intraclass correlations were high for tasks, meaning that within each task, all participants performed similarly. Thus, only frequency has a tendency to show a common time-based process within a participant, but common time-based processes exist between participants.

From walking to running: applying a dynamical systems approach to the development of locomotor skills.

Developmental transitions of complex systems may be studied by selecting (collective) variables that constrain the degrees of freedom for each developmental state. In a dynamical systems approach, the transitions from state to state are engendered through the scaling of contributing subsystems (control parameters). In this study, the locomotor skills of walking and running were compared in newly running infants by observing several likely collective variables including relative stance, estimated pathway of center of mass, and segmental/joint action. 4 children were filmed longitudinally at 5.5, 7.5, and 9.5 months of independent walking and then at 3 years of age. 3 trials per gait were selected for single stride analysis and compared with data from 4 adults. In general, the proposed collective variables showed transitional forms over the first few months of running, indicating a relatively continuous change between the 2 gait forms. Coordination of the knee joint was very similar between gaits and across age, but the ankle joint was less consistent for both gaits in the infants. Relative stance and stride length data indicated that the children could not generate vertical and horizontal displacement. These findings echo those found in newly walking infants and suggest that similar rate-limiting parameters are present for both gaits.

A comparison of two criterion-referenced standard setting procedures for sports skills testing.

The application of criterion-referenced (CR) standard setting procedures in physical education has been limited to the examinee-centered model known as criterion groups. Alternative examinee-centered approaches are available but have not been applied in sport skills testing. The purpose of this study was to compare two examinee-centered models for setting performance standards for a sport skills test battery. CR performance standards were determined for the tennis skills test battery published in Tennis skills test manual (Hensley, 1989) using the borderline group (BG) (Livingston & Zieky, 1982) and criterion groups (CG) (Berk, 1976) models. The comparison of these two methods demonstrated that the CG method consistently produced performance standards that were lower than the BG method. In one instance the BG method produced a standard that was clearly unreasonable. Estimates of CR reliability for the CG standards (.76 less than or equal to P less than or equal to .93; .52 less than or equal to Kq less than or equal to .86) were higher than BG estimates (.55 less than or equal to P less than or equal to .84; .11 less than or equal to Kq less than or equal to .68). Although each method has strengths, neither is without problems. Results from this study suggest these two methods might be combined to minimize the problems associated with each. This combined method should produce standards with improved accuracy, validity, and reliability.