Motor development research : I. The lessons of history revisited (the 18th to the 20th century)

In 1989, Clark and Whitall asked the question “What is motor development”. They were referring to the study of motor development as an academic research enterprise and answered their question primarily by describing four relatively distinct time periods characterized by changes in focus, theories or concepts and methodology. Their last period was named the process-oriented period (1970-1989). In hindsight, it seems clear that their last period could be divided into two separate historical time periods: the information-processing period (1970-1982) and the dynamical systems period (1982-2000). In the present paper, we briefly revisit the first three periods defined by Clark and Whitall, and expand and elaborate on the two periods from 1970 to the turn of the century. Each period is delineated by key papers and the major changes in focus, theories or concepts and methodology. Major findings about motor development are also described from some papers as a means of showing the progression of knowledge

Age-Related Differences in Kinematics, Kinetics, and Muscle Synergy Patterns Following a Sudden Gait Perturbation: Changes in Movement Strategies and Implications for Fall Prevention Rehabilitation

Falls in older adults are leading causes of fatal and non-fatal injuries, negatively impacting quality of life among those in this demographic. Most elderly falls occur due to unrecoverable limb collapse during balance control in the single-limb support (SLS) phase. To understand why older adults are more susceptible to falls than younger adults, we investigated age-related differences in lower limb kinematics, kinetics, and muscle synergy patterns during SLS, as well as their relationship to postural control strategies. Thirteen older and thirteen younger healthy adults were compared during the SLS phase of balance recovery following an unexpected surface drop perturbation. Compared to younger adults, older adults demonstrated (1) greater trunk flexion, (2) increased hip extension torque and reduced hip abduction torque of the perturbed leg, and (3) higher postural sway. Trunk flexion was correlated with a delayed latency to the start of lateral-to-medial displacement of center of mass from the perturbation onset. The group-specific muscle synergy revealed that older adults exhibited prominent activation of the hip extensors, while younger adults showed prominent activation of the hip abductors. These findings provide insights into targeted balance rehabilitation and indicate ways to improve postural stability and reduce falls in older adults

A Clinically Relevant Method of Analyzing Continuous Change in Robotic Upper Extremity Chronic Stroke Rehabilitation

Background. Robots designed for rehabilitation of the upper extremity after stroke facilitate high rates of repetition during practice of movements and record precise kinematic data, providing a method to investigate motor recovery profiles over time. Objective. To determine how motor recovery profiles during robotic interventions provide insight into improving clinical gains. Methods. A convenience sample (n = 22), from a larger randomized control trial, was taken of chronic stroke participants completing 12 sessions of arm therapy. One group received 60 minutes of robotic therapy (Robot only) and the other group received 45 minutes on the robot plus 15 minutes of translation-to-task practice (Robot + TTT). Movement time was assessed using the robot without powered assistance. Analyses (ANOVA, random coefficient modeling [RCM] with 2-term exponential function) were completed to investigate changes across the intervention, between sessions, and within a session. Results. Significant improvement (P < .05) in movement time across the intervention (pre vs post) was similar between the groups but there were group differences for changes between and within sessions (P < .05). The 2-term exponential function revealed a fast and slow component of learning that described performance across consecutive blocks. The RCM identified individuals who were above or below the marginal model. Conclusions. The expanded analyses indicated that changes across time can occur in different ways but achieve similar goals and may be influenced by individual factors such as initial movement time. These findings will guide decisions regarding treatment planning based on rates of motor relearning during upper extremity stroke robotic interventions

Treadmill exercise activates subcortical neural networks and improves walking after a stroke

BACKGROUND AND PURPOSE: Stroke often impairs gait thereby reducing mobility and fitness and promoting chronic disability. Gait is a complex sensorimotor function controlled by integrated cortical, subcortical, and spinal networks. The mechanisms of gait recovery after stroke are not well understood. This study examines the hypothesis that progressive task-repetitive treadmill exercise (T-EX) improves fitness and gait function in subjects with chronic hemiparetic stroke by inducing adaptations in the brain (plasticity).METHODS: A randomized controlled trial determined the effects of 6-month T-EX (n=37) versus comparable duration stretching (CON, n=34) on walking, aerobic fitness and in a subset (n=15/17) on brain activation measured by functional MRI.RESULTS: T-EX significantly improved treadmill-walking velocity by 51% and cardiovascular fitness by 18% (11% and -3% for CON, respectively; P&lt;0.05). T-EX but not CON affected brain activation during paretic, but not during nonparetic limb movement, showing 72% increased activation in posterior cerebellar lobe and 18% in midbrain (P&lt;0.005). Exercise-mediated improvements in walking velocity correlated with increased activation in cerebellum and midbrain.CONCLUSIONS: T-EX improves walking, fitness and recruits cerebellum-midbrain circuits, likely reflecting neural network plasticity. This neural recruitment is associated with better walking. These findings demonstrate the effectiveness of T-EX rehabilitation in promoting gait recovery of stroke survivors with long-term mobility impairment and provide evidence of neuroplastic mechanisms that could lead to further refinements in these paradigms to improve functional outcomes

Reflections on motor development research across the 20th century : six empirical studies that changed the field

Motor development research has had a rich history over the 20th century with a wide array of scientists contributing to a broad and deep body of literature. Just like the process of development, progress within the field has been non-linear, with rapid periods of growth occurring after the publication of key research articles that changed how we conceptualized and explored motor development. These publications provided new ways to consider developmental issues and, as a result, ignited change in our theoretical and empirical approaches within the field of motor development and the broader field of developmental psychology. In this paper, we outline and discuss six pioneering studies that we consider significant in their impact and in the field's evolution, in order of publication: Halverson, 1931; Wild, 1938; Gibson & Walk, 1960; Connolly, Brown, & Bassett, 1968; Thelen & Fisher, 1982; Thelen & Ulrich, 1991. We have limited this review to empirical papers only. Together, they offer insight into what motor development research is, where it came from, why it matters, and what it has achieved

The developmental effect of concurrent cognitive and locomotor skills: time-sharing from a dynamical perspective

A dynamical systems perspective on neuromuscular behavior was used to predict the effect of concurrent verbal cognition on locomotor skills. Fundamental to this perspective is the distinction between coordination (collective) variables which define the movement's pattern and control variables which specify the overall parameters of the movement (e.g., velocity). Only the latter were predicted to show interference in the dual-task situation. Female subjects ranging from 2.5 years to adults were filmed while running and galloping both with and without concurrent vocal and nonvocal tasks. Cinematographic analysis revealed no interference on the coordination variables across age but some interference on the control variables which increased in the younger age groups. The younger children had problems with initiating two neuromuscular tasks simultaneously but once initiated the coordination was unaffected. The results suggest that the coordination of a gait requires less attention than the setting of control parameters and that the former is in place at an early ag