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This paper examined relationships between qualitative (developmental sequences) and quantitative (time) performance in rising from a supine position in early childhood. One hundred twenty two children ranging in age from 3 to 5 years were videotaped for five trials of rising from a supine position. Children’s performance on the supine-to-stand (STS) task was quite variable in terms of both qualitative movement patterns and time (mean = 2.37 s, SD = .60). Results: Component sequences were moderately to strongly correlated with each other (r = .387 to .791). Upper-extremity (r = –.383) and axial (r = –.416) component levels also were inversely correlated with STS time. Results indicated a strong coordinative link between the development of trunk control (i.e., axial movement) and upper-extremity movement levels (r = .791), and together they demonstrated the strongest impact on the ability to rise quickly. These data provide important information relating to a child’s motor development that may have clinical relevance for diagnosis. It provides also a greater understanding on how to improve performance on this task. Future research should examine qualitative and quantitative aspects of STS performance to understand its predictive utility as a lifespan assessment of motor competence and its potential importance as a measure to predict healthrelated variables and functional capability across the lifespan.

We conducted a longitudinal kinematic study of spontaneous arm and leg motions in 4 supine infants at 3, 4½, and 6 months of age. The study addressed two questions: (a) whether there was a longitudinal change in the synchronization of joint rotations at the hips, knees, shoulders, and elbows, indicating that the arms and legs were moving more independently of each other; and (b) whether, during this period, the spatial location of the hands relative to the shoulders was different from that of the feet relative to the hips, indicating that the infants were beginning to use their upper limbs differently than their lower limbs. We found that, in general, the arms and legs were moving more independently of each other by 6 months of age. At the same time, the infants were more likely to hold their hands away from the body in preparation for making contact with an object in the midline, but they brought their feet close to the body to maximize propulsive kicks. Thus, a reorganization of the relative timing of joint rotations appears to be related to the emergence of different arm and leg functions.

Individual body segment actions evolve during throwing skill development. Maximal trunk involvement is typically the last feature of the movement pattern to fully develop. The current study examined developmental levels of trunk action and the associated variability in the throwing motion. The throwing motions of children and adolescents were analyzed via motion capture and trunk actions were classified as exhibiting no rotation (n = 7), blocked rotation (n = 6), or differentiated rotation (n = 11). Results indicated nonrotators exhibited greater variability than blocked-rotators in maximum humeral external rotation and humeral horizontal adduction angles at ball release; nonrotators also demonstrated greater variability than differentiated-rotators on these parameters, in addition to forward trunk tilt and elbow extension angle at ball release. Nonrotators produced more variable peak upper torso and humeral horizontal adduction angular velocities, as well as peak upper torso linear velocity, relative to differentiated-rotators. Blocked-rotators produced more variable peak pelvis, upper torso, and humeral horizontal adduction angular velocities, as well peak pelvis linear velocity, relative to differentiated-rotators. Nonrotators were less consistent relative to blocked- and differentiated-rotators in the time that elapsed from peak pelvis angular velocity to ball release. These results indicate that greater trunk involvement is associated with more consistent movement production.

According to the constrained action hypothesis, an external focus of attention is beneficial for motor learning due to improvements in movement automization. In contrast, an internal focus of attention interferes with automaticity and decreases the effects of motor learning. This study was designed to test the automaticity assumption of the focus of attention effect within a highly skilled population. We examined the effects of attentional focus on kinematics in rope jumping and visual control. Participants practiced the rope-jumping task over five days of acquisition, which was followed by a retention and transfer test. The findings provided evidence that the learning of the task was improved and automaticity was increased by the external focus compared with the internal focus and no attentional (i.e., control condition) conditions. In addition, these findings indicate that visual attention as a function of attentional focus has a stronger relationship with practice performance rather than with motor learning effects.

We investigated the coordination of balance and propulsion processes in learning to ride a unicycle through a principal component analysis (PCA) of the nature and number of functional degrees of freedom (DOF) in the movement coordination patterns. Six participants practiced unicycle riding on an indoor track for 28 sessions over separate days. The movement time and performance outcomes were recorded for each trial and body segment kinematics were collected from the first and every succeeding 4th session. The first appearance of no-hand-support performance varied across participants from the 5th practice session to the 22nd session. The PCA showed that initially in practice the 39 kinematic time series could be represented by 6–9 components that were reduced over practice to 4–7 components. The loadings of the PCA that reflected balance and propulsion processes became more coupled as a function of successfully riding the unicycle. The findings support the proposition that learning to ride the unicycle is a process of making the system more controllable by coordinating balance and propulsion while mastering the redundant DOF.

In this experiment, we investigated the role of practice variability (constant versus variable practice) and practice schedule (random versus blocked practice) on spatial and temporal learning of a speech task as a function of aging. The participants were 80 healthy individuals (40–80 years) with no history of cognitive, sensory, or motor disorders. A median split was performed to divide the participants into older and younger groups. The median split was at 59 years of age, thus placing 40 participants in each age group. The participants were assigned to one of four practice groups and practiced a nonmeaningful phrase for two consecutive days. On the third day, the participants reproduced the speech phrase without practice. Data analysis revealed that older participants involved in constant practice demonstrated superior temporal learning of the speech task over participants on variable practice. Older participants on random practice demonstrated better spatial learning of the speech task than did participants on blocked practice. In contrast, there was no effect of practice conditions on spatial and temporal learning outcomes in the younger group. The findings indicate that practice variability and practice schedule influence different aspects of a complex speech-motor learning task among older adults but not among younger adults.