The uncontrolled manifold approach was used to examine the effect of workspace location on the use of motor abundance to control the hand’s path during reaching. Participants pointed to targets located in the contralateral and ipsilateral workspaces at two different distances. When reaching to all parts of the workspace, the component of joint configuration variance consistent with an identical hand path across trials was significantly higher than the component of joint configuration variance leading to a variable hand path. The relative magnitude of this difference was affected primarily by target orientation and minimally by target distance. The control of hand-path direction when reaching ipsilaterally was associated with more selective use of motor abundance compared to reaching contralaterally. The control of hand-path extent was not affected by target orientation. Biomechanical factors are discussed as possible reasons that lead to the observed selective workspace effects.
Ya-weng Tseng and John P. Scholz
Geetanjali Gera, Sandra Freitas, Mark Latash, Katherine Monahan, Gregor Schöner and John Scholz
This study investigated the use of motor abundance during the transport and placing of objects that required either precise or minimal orientation to the target. Analyses across repetitions of the structure of joint configuration variance relative to the position and orientation constraints were performed using the Uncontrolled Manifold (UCM) approach. Results indicated that the orientation constraint did not affect stability of the hand’s spatial path. Orientation was weakly stabilized during the late transport phase independent of the orientation constraint, indicating no default synergy stabilizing orientation. Stabilization of orientation for conditions most requiring it for successful insertion of the object was present primarily during the adjustment phase. The results support the hypothesis that a major advantage of a control scheme that utilizes motor abundance is the ability to resolve multiple task constraints simultaneously without undue interference among them.
Mark L. Latash
eliminated. This is particularly puzzling given another very well known expression by Bernstein: “repetition without repetition”, implying variable means of performing actions over repetitive trials. The Principle of Abundance and the Uncontrolled Manifold Concept An alternative view at the problem of
Edited by Mark Latash
It is suggested that the famous problem of motor redundancy is inapplicable to human voluntary movements. Such notions as “the elimination of biomechanical degrees of freedom” should not be used in human movement studies. During natural movements, elements within apparently redundant sets are all involved in solving motor tasks. The abundance of elements is a keystone forming the foundation of motor synergies. It allows natural movements to display both flexibility and stability.
Momoko Yamagata, Ali Falaki and Mark L. Latash
, including standing, involve large (abundant, Latash, 2012 ) sets of effectors such as joints and muscles. The principle of abundance ( Gelfand & Latash, 1998 ) views this apparently redundant design of the body as an important mechanism that allows stabilizing different performance variables in a task
Thomas M. Newman, Giampietro L. Vairo and William E. Buckley
incidence of repetitive sprains. Although an abundance of literature exists focusing on the efficacy of braces in preventing ankle sprains in young, healthy, and physically active populations, there is a scarcity of evidence specific to the impact of these apparatuses on functional performance; therefore
Mark L. Latash
The target article presents a review of the neural control of the human hand. The review emphasizes the physical approach to motor control. It focuses on such concepts as equilibrium-point control, control with referent body configurations, uncontrolled manifold hypothesis, principle of abundance, hierarchical control, multidigit synergies, and anticipatory synergy adjustments. Changes in aspects of the hand neural control with age and neurological disorder are discussed. The target article is followed by six commentaries written by Alexander Aruin, Kelly Cole, Monica Perez, Robert Sainburg, Marco Sanello, and Wei Zhang.
Daniel A. Gruber
This article presents a case study of the developments in media gatekeeping in the last 10 years, focusing on the launch of the Tennis Channel and the ascendance of ESPN as the major network for professional tennis in the United States. The U.S. broadcast networks NBC and CBS have ceded the exclusive television rights for 2 of the Grand Slam tournaments (Wimbledon, U.S. Open) to ESPN for the first time in over 40 years. Meanwhile, the Tennis Channel, despite its independence from the media conglomerates, has carved out a niche for fans with its extensive global coverage of tournaments and for advertisers with its lucrative audience demographics. This change in dominance after the broadcast networks reigned for over 4 decades underscores the globalization of the sport and the abundance of early-round tournament matches available to fans. Organizational theories are used to analyze what has occurred and to predict what will happen next for tennis media gatekeeping in the United States.
Russell E. Ward
Durkheim’s discussion on ritual and Goffman’s theoretical work on first impressions are used to predict superior performance among home teams on opening day. Information on opening day game outcomes is compiled and compared with the results of regular season and championship play. The analysis reveals a greater home advantage for teams playing in opening day games than for home teams competing in regular season or championship games. When controlling for the effect of stadium attendance on the home advantage, the opening day home advantage exceeds that of championship competition. The results suggest that ritual activity and concerns for first impression management may be factors that condition home team performance, offering support for the assertion that performance is partly a social product. Further home advantage research can direct attention to cross-cultural differences in the opening day home advantage and focus on qualitative data collection to supplement the current abundance of archival data.
Mark L. Latash
The article offers a way to unite three recent developments in the field of motor control and coordination: (1) The notion of synergies is introduced based on the principle of motor abundance; (2) The uncontrolled manifold hypothesis is described as offering a computational framework to identify and quantify synergies; and (3) The equilibrium-point hypothesis is described for a single muscle, single joint, and multijoint systems. Merging these concepts into a single coherent scheme requires focusing on control variables rather than performance variables. The principle of minimal final action is formulated as the guiding principle within the referent configuration hypothesis. Motor actions are associated with setting two types of variables by a controller, those that ultimately define average performance patterns and those that define associated synergies. Predictions of the suggested scheme are reviewed, such as the phenomenon of anticipatory synergy adjustments, quick actions without changes in synergies, atypical synergies, and changes in synergies with practice. A few models are briefly reviewed.