The Influence of Contraction Types on the Relationship Between the Intended Force and the Actual Force

Abstract

It has been demonstrated that the intended force (subjective estimation of force) does not always match to actual force without external feedback. The purpose of this study was to compare the influence of ballistic and tonic contractions on the relationship between the intended and actual force. Subjects produced isometric force at requested percentages of their MVC (20, 40, 60 and 80%) based on subjective estimation of force under two conditions (tonic and ballistic conditions). The tonic condition was to maintain force production, whereas the ballistic condition was to produce force as fast as possible. As a result, the actual force amplitude, the coefficient of variance and EMG amplitude were larger under the ballistic contraction compared with the tonic condition, even the same intended force levels. These results suggest that different motor unit activity and control systems in the ballistic and tonic contractions could alter the relationship between the intended force and the actual force.     

Muscle Damaging Exercise Affects Isometric Force Fluctuation as well as Intraindividual Variability of Cognitive Function

Healthy untrained men (N = 11) were asked to perform 10 series of 12 repetitions of knee eccentric extension (EE) at 160° per second. Quadriceps muscle torques evoked by electrical stimulation at 20 Hz (P20) and 100 Hz (P100), maximal voluntary isometric contraction torque (MVC), maximal isokinetic concentric torque (IT) at 30° per second, voluntary activation index (VA), simple reaction time (RTs), complex reaction time (RTc), and torque variability at 30% of MVC were measured before EE, immediately after EE, and 60 min and 24 hr after EE. MVC, IT, P20, P100, and VA decreased significantly after EE and remained depressed 24 hr later. Torque variability increased significantly after EE. Average RTs and RTc did not change after EE, whereas intraindividual variability in RTs and RTc increased significantly after EE.     

The Effects of Force and Direction Uncertainty on Choice Reaction Time in an Isometric Force Production Task

The two experiments reported examined the temporal organization of force and direction motor-programming processes in a step-input tracking type task. Both experiments observed a reduction in reaction time in the direction-uncertain conditions compared to the direction-certain ones. Thus it seems as though the direction decision does not have to precede the selection of the proper amount of force. Experiment 2 observed an underadditive interaction between levels of direction uncertainty (certain or uncertain) and levels of force uncertainty (certain or uncertain). This interaction was interpreted as support for a parallel organization of the processes responsible for the programming of force and direction and thus, strongly supports the parallel model of programming recently proposed by Klapp (1977a, b).     

Influence of Strategy on Muscle Activity During Impact Movements

Participants (N = 10) made flexions or extensions about the elbow. Movements either were pointing (i.e., self-terminated) or terminated by impact on a barrier. The author examined how the trajectory and the electromyographic (EMG) patterns varied according to the distance moved, the instruction provided concerning speed, or the type of termination. Variations in kinematics induced by changes in the target distance or the instruction regarding speed were the same for impact and pointing movements. In comparison with a pointing movement of similar distance and speed instruction, an impact movement (a) accelerated longer and reached a higher velocity, (b) had a longer agonist EMG burst, and (c) had a low level of contraction that started slightly after the agonist burst and continued throughout the movement but had little or no antagonist burst. Because the different types of movements required different forces from the muscles, there were systematic, task-specific differences in EMG patterns that reflected task-specific differences in central control. The results of this experiment demonstrate that impact movements share some of the rules used in the control of other tasks, such as pointing and reversing movements. The sharing is not imposed by mechanical or physiological constraints but, rather, represents the imposition of internal constraints.     

The Influence of Color and Demand Characteristics on Muscle Strength and Affective Ratings of the Environment

Demand characteristics may influence claims that the color pink inhibits muscle strength whereas blue increases muscle strength. In Experiment 1, undergraduates (N = 59; 30 women, 29 men) were told either that the experimenters thought pink would increase and blue decrease strength or that blue would increase muscle strength and pink decrease muscle strength. A hand dynamometer assessed grip strength as subjects stared at each of 8 differently colored panels. Results indicated that men viewing the pink or orange panels had higher grip strength under pink-strengthen than under pink-weaken instructions. The reverse relationship was found for men viewing a green panel. For women, the pink-weaken instructions resulted in a higher grip strength than did the pink-strengthen instructions, regardless of actual color present. In Experiment 2, women in a no-instruction control condition had lower grip strength than women given the pink-weaken instructions. For men, the control (no-instruction) condition resulted in higher grip strength than the pink-weaken condition. Results of both studies suggest that men followed overt demand characteristics but that women reacted with increased intensity to any suggestion that a stereotypically feminine pink is associated with weakness.     

Variation of Isometric Response Force in the Rat

Hungry, unrestrained rats (N = 7) were rewarded for pressing a response beam in excess of 11 different force requirements. Changes in peak force production as a function of peak force requirement were examined by analyses of the first four moments of distributions of peak response forces: constant error, the within-subject standard deviation, skewness, and kurtosis. Results were similar to those previously obtained with human subjects: Constant error was positive at low and negative at high force requirements, the within-subject standard deviation increased as a negatively accelerating function of force requirement, and skewness and kurtosis were positive at low force requirements and decreased to negative values at the highest increments. Additional analyses of response kinetics indicated that rats, like humans, meet increasing force requirements by altering the rate of rise of force. The performance similarities suggest that common processes are engaged by the human and rat motor control systems to solve the problem of generating forces that are appropriate to the prevailing environmental constraints.     

Variation of Isometric Response Force in the Rat

Hungry, unrestrained rats (N = 7) were rewarded for pressing a response beam in excess of 11 different force requirements. Changes in peak force production as a function of peak force requirement were examined by analyses of the first four moments of distributions of peak response forces: constant error, the within-subject standard deviation, skewness, and kurtosis. Results were similar to those previously obtained with human subjects: Constant error was positive at low and negative at high force requirements, the within-subject standard deviation increased as a negatively accelerating function of force requirement, and skewness and kurtosis were positive at low force requirements and decreased to negative values at the highest increments. Additional analyses of response kinetics indicated that rats, like humans, meet increasing force requirements by altering the rate of rise of force. The performance similarities suggest that common processes are engaged by the human and rat motor control systems to solve the problem of generating forces that are appropriate to the prevailing environmental constraints.     

The Influence of Individual Attitudes on Construction of an Attitude Scale

Summary

The importance of talkativeness or the relative frequency of contributing to task interaction was examined as a factor which determines person perception. Both the quality and frequency of comments made in a two-person interaction were controlled by using experimental confederates who performed prescribed roles. Quantity but not quality of task contributions was significantly related to the attribution of creativity, and influence over others.     

眼外肌Pulley研究进展及分析

随着影像学、形态学、计算机等多学科在眼科的应用,眼外肌Pulley得以被发现并被应用于临床研究.眼外肌Pulley的应用使临床眼球运动Listing法则,前庭眼反射及双眼集合运动理论得到了较为全面的解释.在众多学科的研究基础上,眼外肌Pulley对某些复杂斜视的发病机制有了新的解释并对其临床治疗提供了新的手术方法.     

Influence of accommodation on the viewing of an optical illusion

This study demonstrates the role of microfluctuations of accommodation in the viewing of the concentric ring illusion. Four experiments were carried out. Experiment I consisted of changing the distance between the illusion and the eyes but retaining visual angle, luminance and pupil size constant. In Experiment II, the accommodation of the eyes is paralysed by a cycloplegic. In Experiment III, the illusion is shown to a monocular aphakic and in Experiment IV, the exposure time is varied between 1/100 and 5 sec. Furthermore, a series of observations compared the concentric ring illusion seen with both eyes simultaneously. The evidence provided by the results of these experiments plus others discussed provide evidence that the concentric ring illusion is caused by the microfluctuations of accommodation.     

The Effects of Progressive Muscle Relaxation on the Behavior of Autistic Adolescents:

Five autistic adolescents were trained in the use of progressive muscle relaxation to determine the effects of the relaxation training on task-oriented, disruptive, and stereotypic behavior, in a structured academic session. Each academic session was 12 minutes in length. Prior to each session, the children engaged in one of two activities with the relaxation trainer for 10 minutes, i.e., the practice at relaxation or a Simon-says game. Measures of disruption, on-task, and academic rate were gathered in the 12-minute academic session. In addition, a relaxation checklist was used to determine the extent to which the child was relaxed in the relaxation sessions. The results gave little evidence of differential effects as a consequence of the relaxation procedures on any of the dependent measures. The addition of relaxation cues during academic sessions failed to produce any change in the children's behaviors.     

The Finite Model Property for the Implicational Fragment of IPC Without Exchange and Contraction

The aim of this paper is to show that the implicational fragment BKof the intuitionistic propositional calculus (IPC) without the rules of exchange and contraction has the finite model property with respect to the quasivariety of left residuation algebras (its equivalent algebraic semantics). It follows that the variety generated by all left residuation algebras is generated by the finite left residuation algebras. We also establish that BKhas the finite model property with respect to a class of structures that constitute a Kripke-style relational semantics for it. The results settle a question of Ono and Komori [OK85]. This revised version was published online in June 2006 with corrections to the Cover Date.     

The Effect of Paired Muscle Stimulation on Preparation for Movement

Paired muscle stimulation is used clinically to facilitate the performance of motor tasks for individuals with motor dysfunction. However, the optimal temporal relationship between stimuli for enhancing movement remains unknown. We hypothesized that synchronous, muscle stimulation would increase the extent to which stimulated muscles are concurrently prepared for movement. We validated a measure of muscle-specific changes in corticomotor excitability prior to movement. We used this measure to examine the preparation of the first dorsal interosseous (FDI), abductor digiti minimi (ADM), abductor pollicis brevis (APB) muscles prior to voluntary muscle contractions before and after paired muscle stimulation at four interstimulus intervals (0, 5, 10, and 75 ms). Paired muscle stimulation increased premovement excitability in the stimulated FDI, but not in the ADM muscle. Interstimulus interval was not a significant factor in determining efficacy of the protocol. Paired stimulation, therefore, did not result in a functional association being formed between the stimulated muscles. Somatosensory potentials evoked by the muscle stimuli were small compared to those commonly elicited by stimulation of peripheral nerves, suggesting that the lack of functional association formation between muscles may be due to the small magnitude of afferent volleys from the stimulated muscles, particularly the ADM, reaching the cortex.     

The Effects of Competition on the Decision Quality of Diverse and Nondiverse Groups

Research has validated that intragroup cooperation, rather than competition, produces more positive group interaction and interpersonal acceptance which leads to better performance. The unique values of culturally diverse group members, however, may influence group processes and performance if these group members respond differently to situational cues. Research on the interaction between cultural diversity and competitive team situations would benefit organizations that employ an increasingly diverse work force. The primary purpose of this study is to explore the effects of cultural diversity on group performance and group processes by comparing culturally diverse and culturally nondiverse groups under conditions of intergroup competition and noncompetition. This experiment was conducted using 500 upper-level undergraduate students enrolled in a principles of management course at a large university in the southwestern United States. The results of this experiment indicate that the competitive nondiverse groups performed better than did the noncompetitive diverse groups in terms of quality of performance. Results also suggest that both the culturally diverse and culturally nondiverse groups outperformed their best individual members' scores when they were matched with competitive situations that enhanced their innate group processing styles. Organizations can increase their effectiveness by appreciating that diverse and nondiverse groups respond differently under conditions of competition and noncompetition.     

The Effects of Cooperation and Competition on Ingroup-Outgroup Bias1

A matrix game format was employed in a 2 × 2 design to study the effects of within group cooperation and competition under conditions of success and failure on subjects' subsequent treatment of own group and outgroup persons. Subjects in two-person groups either succeeded or failed at a cooperative or competitive game and then awarded points (worth money) to themselves, their partner, and two other people. A review of the relevant literature suggested that ingroup-outgroup bias would be greater after successful competition than after unsuccessful competition. The results supported this hypothesis. It was also found that subjects in the Cooperation-Failure condition displayed greater ingroup-outgroup bias than subjects in the Cooperation-Success condition. A qualification of the previous research supporting a positive relationship between group cohesiveness and ingroup-outgroup bias was suggested on the basis of the results.     

The Causal Efficiency of the Passage of Time

Does mere passage of time have causal powers? Are properties like ??being n days past?? causally efficient? A pervasive intuition among metaphysicians seems to be that they don??t. Events and/or objects change, and they cause or are caused by other events and/or objects; but one does not see how just the mere passage of time could cause any difference in the world. In this paper, I shall discuss a case where it seems that mere passage of time does have causal powers: Sydney Shoemaker??s (1969) possible world where temporal vacua (allegedly) take place. I shall argue that Shoemaker??s thought-experiment doesn??t really aim at teaching us that there can be time without change, but rather that if such a scenario is plausible at all (as I think it is) it provides us with good reasons to think that mere passage of time can be directly causally efficient.     

Influence of numerical magnitudes on the free choice of an object position

The link between numerical magnitude and mechanisms of spatial orienting has been underlined in an increasing number of studies. Similarly, the relationship between numerical magnitude and grasping actions has started to be investigated. The present study focuses on the influence of numerical magnitude processing in the free choice of the position of an object. Participants were presented with a digit (1-9 without 5) and were required to decide whether it was smaller or larger than 5. Then, they had to grasp a small cube and change its position before vocally responding "higher" or "lower". Results showed that in the initial phase of the grasp movement, the grip aperture was modulated by the numerical magnitude. Moreover, participants shifted the position of the cube more leftward with smaller digits compared with larger ones, and they tended to position the object closer to themselves with smaller digits compared with larger ones. These results extend the previous findings indicating that the processing of magnitude is tightly related to the mechanisms of spatial orienting that subserve action execution.     

工作记忆内容对不同学业水平学生自上而下注意控制的影响

该研究采用视觉搜索任务范式,以小学五年级学优生与学困生为被试,探讨了工作记忆内容对不同学业水平学生自上而下注意控制的影响。结果发现:(1)学优生与学困生的自上而下注意控制能力存在显著差异,学优生的反应时显著短于学困生;(2)工作记忆内容影响自上而下注意控制,靶相关信息能促进对靶刺激的搜索,而靶无关信息却会干扰对靶刺激的搜索。