Karl M. Newell
Karl M. Newell
A review and synthesis of the literature on the learning and development of motor skills supports the postulation that whether a motor skill can be deemed fundamental is dependent on the collective presence of three conditions: (i) uniqueness to the movement pattern and/or outcome; (ii) near universality of the functional outcome in the healthy population; (iii) capacity to act as an antecedent influence supporting generalization to a large and broad set of perceptual-motor skills. Within this framework, it is proposed that the infant motor development sequence underpinning upright posture (e.g., sitting, bipedal standing), locomotion (e.g., walking, running), and object-interaction (e.g., grasping) represents the minimum set of fundamental motor skills from which all other skills evolve with over the lifespan. This position is in contrast to the views of many students of motor development and learning who describe numerous skills that typically emerge in the ∼2- to 18-year-old range as fundamental but do not meet the criteria outlined here to be fundamental. It is proposed that these be labeled as core developmental activities having a more restricted but still practically relevant influence on the acquisition of and generalization to other motor skills.
Karl M. Newell
This paper provides reflections on the progress to date and current status of research in kinesiology. The accompanying overview articles in this special issue of Kinesiology Review show that the contemporary disciplinary/professional foci of kinesiology remain, by and large, the same as the initial research and teaching structures of 50 years ago, as outlined in the inaugural overviews. Nevertheless, within this prevailing disciplinary/professional structure, there have been many new developments in movement-related research, including the juxtaposition of novel alignments and integrations of certain specializations of kinesiology. There is general consensus that the quality and quantity of research in kinesiology have advanced substantially, albeit unevenly, on multiple fronts, both within and between the areas of specialization. The research agenda in kinesiology has benefitted from the growing realization of the centrality of human movement and physical activity in contributing to a healthy lifestyle for individuals and societies.
Karl M. Newell
In this paper I discuss briefly some traditional and contemporary issues that challenge the academic structure of the field of Kinesiology. These include the long-standing polemics of the profession-discipline debate and the fragmentation of the academic content knowledge, together with the more recent challenges of education or health as the umbrella construct and the relation of kinesiology to physical and occupational therapy. It appears that the essence of our persistent problems remains, but it is augmented with related and more contemporary issues. Thus, these continue to be challenging times in kinesiology, as they are for higher education in general, reinforcing the long-held notion that change is the one constant.
Karl M. Newell and Steven Morrison
This paper presents a framework for an evolving dynamical landscape of movement forms and their stability over the lifespan. It is proposed that the complexity and dimensionality of movement forms can expand and contract on a number of growth/decay time scales of change including those of adaptation, development, and learning. The expansion and contraction is reflected in: (1) the range of potential movement forms of the individual in developmental time; and (2) the dimensionality and complexity of any single movement form at a moment of observation given the confluence of individual, environmental, and task constraints. It is postulated that practice, exercise, and fatigue also coalesce to change the time scales of complexity and dimension of movement forms.
Xiaogang Hu and Karl M. Newell
The purpose of this study was to investigate the mechanisms contributing to the different scaling functions between force and force variability in continuous and discrete isometric forces. Muscle forces were simulated with the Fuglevand et al. (1993) model of motor unit recruitment and rate coding, and a range of recruitment and firing properties were manipulated. The influence of time-to-peak force on the discrete force variability was also examined. The results revealed that the peak firing rate, the synchrony between motoneurons, and the recruitment range contributed to the different variability functions in continuous and discrete forces. The shorter time-to-peak force led to higher variability in the peak force. The findings show that the model can produce the distinct properties of the force variability scaling functions in continuous and discrete forces. The simulation results provide preliminary insight into the neuromuscular mechanisms of the different force variability functions in continuous and discrete isometric forces.
Karl M. Newell and Paola Cesari
Smeets and Brenner provide a very clear and useful statement of the work that has been stimulated by Jeannerod's 1984 paper but seem more concerned about the viability of model fitting than model assumptions. The theoretical and practical limitations of viewing “grasping as nothing more than pointing” are noted. We reemphasize the importance in prehension of the union of the hand with the object in the act of realizing a task goal.
Steven Morrison and Karl M. Newell
The relation between limb stiffness and postural tremor in the upper arm was investigated during a pointing task. The task goal was to minimize the amount of motion (tremor) at the index finger under levels of increasing limb stiffness. This study investigated the influence of increasing limb stiffness on the pattern of intra- and interlimb dynamics. The frequency profile of the tremor for all limb segments across all conditions displayed two peaks, one between 2-4 Hz and another between 8-12 Hz. A third, higher frequency component (20-22 Hz) was present in the index finger. Increasing limb stiffness through voluntary co-contraction of antagonistic muscle pairs effectively constrained the segments of the upper limb to increasingly operate as a single biomechanical degree of freedom. Higher levels of limb stiffness typically led to an increase in the frequency and power of the 2-4 and 8-12 Hz peaks. There was also a decrease in the frequency of the 20-22 Hz component of finger tremor. The act of reducing the effective degrees of freedom in joint space through voluntarily stiffening of the upper limbs also resulted in decreased performance as determined by an increase in finger tremor. In the preferred, natural level of limb stiffness, specific intralimb segment relations were observed but there was no significant interlimb coupling. The intralimb segment correlations were characterized by compensatory (out of phase) coupling between the upper arm/forearm and hand/index finger segment pairs of each limb that were organized about the action of the wrist joint. Increasing the degree of limb stiffness led to a decrease in the level of intralimb coupling. The findings suggest that the most efficient mechanism for reducing tremor at the periphery is that of compensatory coupling between relevant intralimb segments with a low level of limb stiffness.
Paola Cesari and Karl M. Newell
Karl M. Newell and Gareth Irwin
This paper examines the influence of task and skill level constraints on the generality of proximal–distal control for within-limb movement coordination. Analysis and synthesis of the experimental findings leads to the proposition that proximal–distal is one of several within-limb patterns of coordination, including: the reverse distal–proximal sequence, simultaneous activation of segments, and other sequence variations of this. The probability of particular patterns occurring is induced by task constraints and skill level of the individual, together with their evolving biomechanical consequences, including: open/closed chain, absorption/propulsion of force, magnitude of momentum, and accuracy/timing. We develop the theoretical perspective that classes of task constraints induce particular types of neuromechanical organization to within-arm or within-leg segment coordination. In this task constraint framework, proximal–distal within-limb organization is a particular rather than a general case for within-limb coordination. The limitations of anatomically-based accounts of directional change for within-limb organization are discussed with reference to a general functional degrees of freedom task constraint framework for movement coordination and control.