Stephen A. Wallace

Sport competition as a dynamical self-organizing system

The existence of structure in sport competition is implicated in the widespread practice of using the information gathered from a past contest to prepare for a future contest. Based on this reasoning, we previously analysed squash match-play for evidence of signature traits from among the stochastic relations between the various types of shot. The mixed findings from these analyses led us to re-analyse squash match-play as a dynamical system. Here, we extend this line of investigation with some suggestions as to how various sports might be described further within this theoretical framework. We offer some examples of dynamical interactions in dyadic (i.e. one vs one) and team (e.g. many vs many) sports, as well as some predictions from a dynamical systems analysis for these types of sports contests. This paper should serve to initiate further research into the complex interactions that occur in sport competition.

An impulse-timing theory for reciprocal control of muscular activity in rapid, discrete movements.

Much remains to be learned about how agonist and antagonist muscles are controlled during the production of rapid, voluntary movements. In an effort to summarize a wide body of existing knowledge and stimulate future research on this subject, an impulse-timing theory is presented which attempts to predict the activity of reciprocal muscles based on certain characteristics of a movement. The basic tenet of the theory is that variables of movement time, movement distance and inertial load have fairly predictable effects on the underlying muscular activity of the agonist and antagonist muscles during the production of rapid and discrete, voluntary movements. The theory is derived from the kinematic work of Schmidt, Zelaznik, Hawkins, Frank and Quinn (1979) and supporting evidence from studies which have used electromyographic (EMG) recordings of agonist and antagonist muscles during rapid movements. Issues related to synergistic muscle control, central and peripheral control of reciprocal muscle activity, muscle control, and neurological disorder and the relationship between impulse-timing and mass-spring control are discussed in the final section.

Temporal constraints in the control of prehensile movement.

Three experiments were conducted to investigate the control of the manipulation (i.e., finger-thumb aperture) and transportation (i.e., wrist velocity) components in prehensile movement (Jeannerod, 1981, 1984). In all experiments, subjects were seated and instructed to grasp a dowel mounted on a joystick following a discrete movement over a set distance. Thus, the amount of dowel movement following the grasp could be determined. In Experiment 1, the tolerance (i.e., the amount of allowable dowel movement) was manipulated using a computer-generated boundary around the dowel. The results indicated that the transportation component changed dependent on the tolerance condition, and there were trends that maximum aperture was also affected. Experiment 2 manipulated both tolerance and dowel size (i.e., diameter) factorially in a within-subject design. Dowel size affected only the manipulation component, supporting Jeannerods (1981) earlier work, but tolerance clearly influenced both components. Experiment 3 investigated Wing, Turton, and Frasers (1986) proposition that speed of movement influences aperture size. Distance and movement time were combined factorially to produce conditions with different average velocities. Maximum aperture was dependent on the movement time rather than the speed of movement. The relation between the control of the components was examined by using a new method of calculating within-trial correlations between aperture size and wrist velocity in Experiments 2 and 3. The correlations were related to the temporal aspects of the movement with higher correlations in the rapid movement time conditions. Also, the temporal occurrence of maximum aperture remained invariant across the different movement conditions. In general, the results suggest a strong functional linkage between the two components, which may be dependent on the temporal characteristics of the movement.

Preselection in Short-Term Motor Memory.

Recent studies by Jones (1974) have posited that accurate movements in short-term motor memory (STMM) are mediated by the subjects ability to preset effector mechanisms and monitor their efferent output. Three experiments were conducted to examine this hypothesis. Experiment 1 involved comparisons between the reproduction of the end-location and the reproduction of the distance of a preselected movement. The results revealed that preselected location was superior to preselected distance, indicating that the efference attached to movement extent was not primary. Experiment 2 examined whether location cues were primarily encoded independent of the movement presentation mode. The subjects recalled target locations under preselected, constrained, and passive movement conditions. Recall in the preselected condition was superior to that in the constrained and passive conditions, which showed no difference, suggesting that afferent location information per se was not totally responsible for recall accuracy. Experiment 3 examined the processing requirements of preselected, constrained, and passive location information by filling the retention interval with interpolated processing activity. While preselected location was clearly superior, the three conditions were not differentially affected by processing activity. These overall findings were interpreted as contrary to Jones (1974) and pointed to the importance of preselection in short-term motor memory.

Distance and movement time effects on the timing of agonist and antagonist muscles: a test of the impulse-timing theory.

The experiment examined the effects of movement time (MT) and distance on the timing at electromyographic (EMG) activity from an agonist and antagonist muscle during rapid, discrete elbow movements in the horizontal plane. According to impulse-timing theory (Wallace, 1981) MT, not distance moved, should have a pronounced effect on the timing of EMG activity (duration of initial agonist and antagonist burst and time to onset of initial antagonist burst). The levels of MT were 100 and 160 msec and the levels of distance were 27 degrees and 45 degrees of elbow flexion. In general support of impulse-timing theory, the results of the three EMG timing measures showed that MT had a more pronounced effect on these measures than distance. In addition, the timing of EMG activity in relation to total MT remained fairly consistent across the four MT-distance conditions.

Temporal constraints in reaching and grasping behavior

Abstract Under specific task conditions, many types of human movement behavior such as speech, locomotion and handwriting exhibit a temporal constraint on the many potential degrees of freedom in the form of relative timing among movement components. In the present experiments, we show evidence of temporal constraints in the control of adult prehensile movement independent of transport duration (experiment 1) and initial conditions (experiment 2). In both experiments, subjects were required to reach and grasp a dowel, mounted vertically on a joystick over a distance of 23 cm. Using light emitting diodes (LEDs) placed on the subjects finger, thumb and forearm, individual LED trajectories were captured on film and later kinematically analyzed. In experiment 1, transport duration varied from 300 to 800 ms and in experiment 2, initial conditions were manipulated by requiring subjects to adopt different initial grip postures. Regardless of these manipulations, little change was observed in the temporal occurrence of maximum aperture and onset of grip closure relative to overall movement duration. Functional coupling between fingers and forearm was indicated by high, within-trial co-variation between aperture size and forearm velocity. These results provide further evidence for a temporal constraint on the individual components of prehensile action.

Decision and response times as a function of movement difficulty in preschool children

WALLACE, STEPHEN A.; NEWELL, KARL M.; and WADE, MICHAEL G. Decision and Response Times as a Function of Movement Difficulty in Preschool Children. CHILD DEVELOPMENT, 1978, 49, 509-512. This experiment determined whether the motor control of preschool children is affected by the amplitude and tolerance of movement. Using the Fitts paradigm, the reaction time (RT) and movement time (MT) to executive movements varying in difficulty were examined over 4 consecutive practice days. Results showed that the amplitude and tolerance of movement did not affect the RT required to initiate movement. However, MT was greatly affected by these variables in a manner predicted by Fittss Law. Also, the difficulty of movement appeared to affect MT of preschool children to a greater degree than that found previously with adults. Information-processing differences between children and adults were used as a tentative explanation for these results.

Conscious Mechanisms in Movement

Publisher Summary This chapter describes the conscious mechanisms in movement. It discusses a diverse body of theory and data that have one feature in common, namely, what is called the preselection effect. There can be no question regarding the generality of the preselection effect—the evidence speaks for itself. The superior reproduction accuracy of preselected movement has been demonstrated with slow to moderate paced movements, rapid movements, and semicontinuous movements . Preselection is at the heart of what is often termed volition—it is a much maligned concept that has been shunned by experimental psychologists in the past. The chapter provides an overview on a particular philosophical position on how the psychology of movement might proceed. It discusses the psychological conceptualizations of behavior, including information-processing models.

Kicking performance in relation to balance ability over the support leg

Balance control is presumed to be a fundamental constraint on the organization of skilled movement. The current experiment explored whether single-leg balance ability predicted kicking performance on the other leg. Thirty-eight participants ranging widely in skill kicked a soccer ball with the right and left legs for maximum accuracy and velocity and performed single-leg balance on a force plate for 30 s with the right and left legs. Significant correlations between single-leg balance and kicking accuracy, but not velocity, were found. Left leg balance was more highly correlated than right leg balance with right (dominant) leg kicking accuracy. However, the same pattern of relations was not seen between single-leg balance and left (non-dominant) leg kicking accuracy. These findings provide preliminary support for the importance of balance ability in kicking performance. The importance of balance in the production of athletic skills is discussed and additional experimental paradigms are suggested that might further our knowledge in this area.

An empirical note on attaining a spatial target after distorting the initial conditions of movement via muscle vibration.

Can ones limb be accurately positioned to a spatial location without a veridical estimate of the initial conditions of movement? The experiment reported here examined this question by distorting perception of a limbs starting position via muscle vibration. Subjects executed rapid flexion movements under no-vibration, contralateral arm vibration, and ipsilateral arm vibration conditions. Vibration was applied to the biceps for 10 sec prior to the start of a reproduction movement. The results showed that vibration on the ipsilateral arm caused a significant increase in reproduction error, relative to the no-vibration and contralateral-vibration conditions. This finding provides additional evidence that accurate knowledge about the initial conditions of movement is a necessary component in positioning a limb.