On the nature of human interlimb coordination.

Movement time varies as a function of amplitude and requirements for precision, according to Fitts' law, but when subjects perform two-handed movements to targets of widely disparate difficulty they do so simultaneously. The hand moving to an "easy" target moves more slowly to accommodate its "difficult" counterpart, yet both hands reach peak velocity and acceleration synchronously. This result suggests that the brain produces simultaneity of action not by controlling each limb independently, but by organizing functional groupings of muscles that are constrained to act as a single unit.

Sex differences in cardiovascular reactivity: effects of the gender relevance of the stressor.

Suggests that sex differences in cardiovascular reactivity (CVR) in past research are a function of differences in cognitive appraisal of stressors as masculine or feminine tasks. In the present study, we examined the role of the gender relevance of the stressor as a mediator of sex differences in CVR. The CVR of male and female college students (n = 95) to the cold pressor test (CPT) was compared under masculine and gender-neutral instructions during an anticipation phase, a stressor phase, and a recovery phase. Men were expected to show greater CVR than women to the masculine CPT but not to the gender-neutral CPT. Results supported this prediction for systolic blood pressure reactivity and heart rate reactivity but not for diastolic blood pressure reactivity. The potential influence of sex differences in appraisal of situations on CVR and coronary heart disease is discussed.

Relationship between mood and blood pressure in the natural environment: an adolescent population.

We examined the relation between psychological variables and blood pressure (BP) as 28 adolescents engaged in their customary activities over a 24-hr period in their natural environment. Each subject had previously participated in a laboratory study of cardiovascular reactivity. During the ambulatory monitoring period, subjects monitored mood state, perceptions of the environment, and ambulatory BP at 30-min intervals. Mood ratings and BP were averaged across the waking hours. Systolic blood pressure (SBP) reactivity to laboratory stressors was significantly correlated with average SBP in the home environment. Ambulatory SBP was positively associated with worried, hostile, depressed, and tense mood ratings as well as perceptions of the environment as hostile, demanding, and noisy. Ambulatory diastolic blood pressure was correlated with hostile, depressed, and upset mood ratings as well as with hostile and demanding perceptions of the environment. In general, average ambulatory BP appeared to be associated with negative emotions and perceptions of the environment.

On the coordination of two-handed movements.

In a set of three experiments, we show that after an auditory "go" signal, subjects simultaneously initiate and terminate two-handed movements to targets of widely disparate difficulty. This is the case when the movements required are (a) lateral and away from the midline of the body (Experiment 1), (b) toward the midline of the body (Experiment 2), and (c) in the forward direction away from the body midline (Experiment 3). Kinematic data obtained from high-speed cinematography (200 frames/sec) point to a tight coordinative coupling between the two hands. Although the hands move at entirely different speeds to different points in space, times to peak velocity and acceleration are almost perfectly synchronous. We believe that the brain produces simultaneity of action as the optimal solution for the two-handed task by organizing functional groupings of muscles (coordinative structures) that are constrained to act as a single unit.

The influence on blood pressure during daily activities of a single session of aerobic exercise.

Previous research has examined the effectiveness of a single session of aerobic exercise in lowering blood pressure responsivity to the subsequent presentation of a nonexercise stressor in the laboratory. This case study was designed to explore the possibility that a single session of aerobic exercise might lower blood pressure for up to 4 hours postexercise as the subject engaged in his usual activities at home and at work. The subject was an untrained, unmedicated, borderline hypertensive who underwent ambulatory blood pressure monitoring as he maintained a normal schedule of activities over a 5-day period. On 2 of the 5 days, the subject exercised at 8:30 AM for 30 minutes at 70% VO2max. Blood pressure readings on days when the subject read for 30 minutes were compared with readings on days when he exercised. He showed an average reduction in systolic blood pressure of 26.4 mm Hg at 2 hours after exercise, 24.2 mm Hg at 4 hours afterward, and 12.2 mm Hg at 9 hours after the exercise. Changes in diastolic blood pressure and heart rate were smaller and less consistent. The authors concluded that the modifying influence of a single session of aerobic exercise on blood pressure responsivity to subsequent laboratory-based stressors may also extend to the natural environment. The discussion addresses theoretical, methodological, and clinical considerations in the use of aerobic exercise to modify excessive blood pressure reactivity.

Sex differences in cardiovascular reactivity as a function of the appraised gender relevance of the stressor.

Previous research suggests that sex differences in cardiovascular reactivity are a function of the gender relevance of the stressor. The authors examined the role of a stressor's gender relevance as a mediator of sex differences in cardiovascular reactivity. The cardiovascular reactivity of 121 male and female college students to the cold-pressor test was compared under feminine- and masculine-relevant stressor instructions. The women were expected to show greater cardiovascular reactivity than the men were to the test relevant to women, whereas the men were expected to show greater cardiovascular reactivity than the women were to the masculine cold-pressor test. Results supported these predictions for systolic blood pressure reactivity, but not heart rate reactivity. Diastolic blood pressure results were mixed. The women showed greater diastolic reactivity than the men did to the feminine-relevant test, but the men did not show greater diastolic reactivity than the women did to the masculine test. The influence of sex differences in cognitive appraisal of situations on cardiovascular reactivity and coronary heart disease is discussed.

The Type A belief system: relationships to hostility, social support, and life stress.

Certain core beliefs may underlie the Type A behavior pattern, predisposing individuals to health problems and impaired interpersonal relationships. Previous studies have revealed that the Type A Cognitive Questionnaire (TACQ), a self-report measure reflecting these beliefs, is indeed related to emotional distress. The current study assessed the TACQ's relationship to aspects of the interpersonal environment, including perceived social support and stressful events. It also investigated the TACQ's relationship to subtypes of hostility (ie, cynicism and paranoid alienation). Subjects were 111 college undergraduate volunteers. As hypothesized, the TACQ was significantly related to poor quality of social support and to greater perceived life stress. The TACQ appeared more strongly related to cynicism than to paranoid alienation. Findings were generally more pronounced for males. The discussion suggests that Type A beliefs may predispose individuals to health problems through impaired interactions with their interpersonal environment.

Virtual design prototyping applied to medical facilities.

Over the past five years, MITRE has developed rapid 3D modeling and immersive environment capabilities that supports the application of virtual environment technology to many traditional and non-traditional domains [1]. This paper provides background information on these capabilities and describes the application of this technology to the experimental design prototyping of operating rooms of the future and to the design and retrofit of existing or proposed medical facilities. These capabilities employ contemporary commercial hardware and software and exploit stereoscopic projection displays and headsets. A unique user interface facilitates object manipulation within these immersive environments and addresses two key areas: 1) Visualization of the contents on the model server or library in a catalog form; and 2) Natural interaction and immersion of the user with the visualized catalog and selected visualized objects in a 3D synthetic environment. A brief discussion of two developing applications of this technology will be presented. In one application example, the modeling environment can be used to synthesize physical replicas (potentially full stereo scale) of actual surgical rooms used for training of medical personnel. Alternatively, it can be employed as the infrastructure for a new form of collaborative interactive visualization, namely, telesurgery. In another example, the rapid modeling capability provides designers, architects and medical personnel with a means of rapidly developing synthetic renderings of (potentially interactive and remotely operative) proposed medical facilities prior to construction. We also discuss key issues needing to be resolved for successful model interchange.

Immediate core buildup of endodontically treated teeth: the rest of the seal.

One primary objective of endodontic therapy is to establish an adequate seal with the root canal filling material. The placement of an immediate amalgam buildup at obturation, in conjunction with rubber dam isolation, allows an endodontic seal to be extended from the foramen to the cavosurface margin. As a result of this immediate buildup, the length of the seal and the longevity of the endodontic treatment are presumably extended. This article describes an effective means of performing the immediate core buildup of endodontically treated teeth.

Visualization at supercomputing centers: the tale of little big iron and the three skinny guys.

Supercomputing centers are unique resources that aim to enable scientific knowledge discovery by employing large computational resources-the "Big Iron." Design, acquisition, installation, and management of the Big Iron are carefully planned and monitored. Because these Big Iron systems produce a tsunami of data, it's natural to colocate the visualization and analysis infrastructure. This infrastructure consists of hardware (Little Iron) and staff (Skinny Guys). Our collective experience suggests that design, acquisition, installation, and management of the Little Iron and Skinny Guys doesn't receive the same level of treatment as that of the Big Iron. This article explores the following questions about the Little Iron: How should we size the Little Iron to adequately support visualization and analysis of data coming off the Big Iron? What sort of capabilities must it have? Related questions concern the size of visualization support staff: How big should a visualization program be-that is, how many Skinny Guys should it have? What should the staff do? How much of the visualization should be provided as a support service, and how much should applications scientists be expected to do on their own?

Mass and velocity: control parameters for throwing patterns.

The purpose of this study was to determine if change in segmental mass and increases in throwing velocity act as control parameters to alter throwing patterns. Twenty participants were categorized into four levels of throwing pattern. Each participant was required to make 10 throws at various velocities within 8 conditions. Conditions resulted from combinations of altered mass of the arm, forearm, and hand. Quantitative and qualitative analyses indicated that changes in segmental mass and release velocity either increased or decreased levels of throwing pattern depending on the initial throwing level. It was concluded that mass and velocity may be control parameters which instigate changes in throwing patterns.

Changes in limb striking pattern: effects of speed and accuracy.

This study investigated the changes in an arm striking pattern as a result of practice and the effects of speed and accuracy requirements on such changes. The task was to strike a baseball-size foam ball from a batting tee adjusted to the height of each subject's iliac crest. Ten righthanded subjects, initially displaying an inefficient striking pattern, volunteered for this study. All subjects performed the task according to the following conditions: (1) speed, (2) accuracy, and (3) speed and accuracy. Each subject completed 10 trials in each condition (randomly ordered) for five consecutive days. A high-speed camera (64 fps) was used to photograph subjects' striking patterns for each condition over the 5-day period. Analysis of variance of joint angles at arm reversal and contact and velocity of hand relative to the glenohumeral axis at contact revealed that subjects initially constrained limb segments to act in a unitary fashion; then, with practice, a more efficient pattern was developed. The requirement of speed was found to enhance a change in limb configuration, whereas the requirement of accuracy, and subsequent reduction in speed, impeded the development of a more efficient striking pattern. Analysis of radial error revealed no differences in accuracies to the target by either condition or day of practice. A graphic analysis of segmental angular momentum versus relative time showed that joint angle changes allowed subjects to transfer angular momentum and thereby increase the velocity of the hand at contact.

Rhythmicity, ritual, and motor performance: a study of free throw shooting in basketball.

The purpose of this study was to determine the importance of timing during an auto-communicative ritual to successful performance. Eight members of a university varsity basketball team served as subjects for this study. Each subject performed 15 free throws in each of four different conditions. Condition 1 required subjects to use their standard free throw ritual prior to shooting. Condition 2 required subjects to maintain the relative timing of ritual behaviors but reduce the absolute time of the ritual by one-half. Condition 3 required that relative timing be maintained but that the absolute time of the ritual be doubled. Condition 4 required the same behaviors and the same absolute time as the standard ritual but that the relative time of the ritual be altered. Data were collected with a 16-mm high-speed camera. Types of behaviors, timing aspects of the ritual, successful attempts, and shot mechanics were dependent measures. Analysis of variance (ANOVA) of dependent measures and Fisher's scores from correlation coefficients of dependent measures indicate that relative timing of behaviors (rhythmicity) is more important to success than the absolute time of rituals. Behaviors most important to free throw success are those that may be totally controlled by the subject and yet remain stable with changing conditions.

Rhythmicity and preperformance ritual: stabilizing a flexible system.

The purpose of this study was to determine: (a) if preperformance behaviors display a consistent rhythm across disparate activities; and (b) the relationship of periodicity for such preperformance routines to successful performance. Seven male volunteers were subjects for this study. Each subject had an established ritual for golf putt, basketball free throw, and tennis serve. Data were collected with a motion-analysis system and video camera while the subjects performed each activity. Dependent measures were types of preperformance behaviors, absolute timing of behaviors, relative timing of behaviors, differences in relative times across activities, and successful performance, and mechanical variables related to performance. Analysis of variance (Subject x Activity) indicated significant main effects and interactions for absolute and relative timing of behaviors. Significant correlations were determined to exist between relative time and success, and differences were found between relative times across activity and successful performance. It was concluded that rituals result from endogenous rhythms and that stable periodicity of behaviors across activities promotes successful performance.

Ritual and free-throw shooting in basketball.

The purpose of this study was to determine the nature and effect of certain highly patterned behaviours utilized prior to free-throw shooting in basketball. Ten female basketball players comprising the varsity squad of Texas Christian University, Fort Worth, Texas, USA served as subjects for this study. Subjects were filmed with a high-speed camera and monitored for heart rate during the performance of 10 free throws in each of two conditions: ritual and non-ritual. For the ritual condition, subjects were given unlimited time and freedom of movement prior to each free-throw attempt. For the non-ritual condition, subjects were not restricted by time, but were instructed to shoot the ball without utilizing any movements other than those required to project the ball to the goal. Dependent measures were characteristics of behaviours, physiological changes measured by heart rates, mechanical data (speed, height and angle of release), and number of successful attempts. Condition x trials analyses of variance and low standard deviation concerning characteristics of behaviours indicated that the idiosyncratic behaviours prior to free-throw shooting were rituals of the auto-communicative type. Results indicated no significant difference between conditions for free-throw success. However, partial correlation between dependent measures and successful free-throw attempts indicated that duration of behaviours was most crucial to free-throw shooting success.

Covariation of mood and blood pressure during daily activities.

The relationship between blood pressure (BP) and self-reported mood states was examined for 49 subjects in their natural environment. Subjects performed their usual activities during a 2-day period and recorded their BP using a semiautomated BP monitor at predetermined intervals. Adjective checklists describing mood states and perceptions of the environment as stressful were completed concurrent with each BP measurement. A correlational analysis of average BP and average mood state ratings was performed along with a paired t-test analysis of mood states associated with high versus low BP. The results show that holding anger in correlated positively with average SBP and negatively with average HR. Neither anger arousal nor the expression of anger arousal was able to distinguish between high and low BP readings. The Type A adjective cluster discriminated between high and low SBP as well as between high and low HR readings. The cluster of negative moods also discriminated between high and low SBP. Perceptions of the environment as hostile and demanding discriminated high versus low SBP and high versus low DBP. The discussion focuses upon the value of repeated-measures designs in examining mood/BP relationships as individuals ambulate in their natural environment.