Decreasing Internal Focus of Attention Improves Postural Control During Quiet Standing in Young Healthy Adults

This experiment was designed to investigate whether and how decreasing the amount of attentional focus invested in postural control could affect bipedal postural control. Twelve participants were asked to stand upright as immobile as possible on a force platform in one control condition and one cognitive condition. In the latter condition, they performed a short-term digit-span memory task. Decreased center-of-gravity displacements and decreased center-of-foot-pressure displacements minus center-of-gravity displacements were observed in the cognitive condition relative to the control condition. These results suggest that shifting the attentional focus away from postural control by executing a concurrent attention-demanding task could increase postural performance and postural efficiency.     

The Relation of Mild Traumatic Brain Injury to Chronic Lapses of Attention

We assessed the extent to which failures in sustained attention were associated with chronic mild traumatic brain injury (mTBI) deficits in cognitive control among college-age young adults with and without a history of sport-related concussion. Participants completed the ImPACT computer-based assessment and a modified flanker task. Results indicated that a history of mTBI, relative to healthy controls, was associated with inferior overall flanker task performance with a greater number of omission errors and more frequent sequentially occurring omission errors. Accordingly, these findings suggest that failures in the ability to maintain attentional vigilance may, in part, underlie mTBI-related cognition deficits.     

Hematological Variations during Aerobic Training of College Women

Abstract

The purpose of this study was to observe the effects of a progressive aerobic training program on hemoglobin concentration (Hb), hematocrit (Hct), red blood cell (RBC) count, mean RBC size (MCV), and mean corpuscular hemoglobin (MCH) of college women (N = 19). Training consisted of jogging (3 × week) one mile per session (Week 1) with a progressive increase in duration to five miles per session (Week 9). Training intensity elicited heart rates between 165–185 beats per minute. Blood samples were taken before training and after approximately two, five, seven, and nine weeks. Maximal oxygen uptake (ml/kg · min^?1) increased significantly during training from 41.2 ± 0.7 ( ± SE) to 44.7 ± 0.7. Initial values of Hb, Hct, RBC count, MCV, and MCH were 14.7 ± 0.13 g/dl, 40.4 ± 0.46%, 4.5 ± 0.5 × 10⁶/mm³, 89.0 ± 1.1/μ³, and 32.4 ± 0.4 μμg respectively. Orthogonal polynominal regression indicated significant decreasing quadratic trends for Hb, Hct, and RBC count, a significant cubic trend for MCV, and no change in MCH during training. Despite the initial trends, values that changed did return to near pretraining levels by the end of the nine-week program. Values for all blood parameters remained within normal ranges throughout the study. These data suggest that although aerobic training of increasing intensity in young women may be accompanied initially by decreases in Hb, Hct, and RBC count and an increase in MCV, these changes are only transitory. If such changes result from RBC destruction rather than hemodilution, the return to hematopoietic balance could impose a draw on body iron stores.     

Premotor and Motor Reaction Time As a Function of Response Complexity

Abstract

Two experiments were conducted to identify the response elements responsible for the complexity effect found by Henry and Rogers (1960). An attempt was made to determine if these elements were affecting the premotor time component of simple reaction time (SRT). If they were, a strong case could be made for the argument that neuromotor programming time was affected because premotor time is a more exact estimate of it than SRT. The results revealed that premotor time was unaffected by a forward change in movement direction, but increased as the number of movement parts increased from one to two and as the demand for movement accuracy increased. Thus, increasing the (1) number of parts and (2) accuracy demands were identified as elements of response complexity which increase programming time and support Henry and Rogers (1960) hypothesis that the time to initiate a response becomes longer as the programming process become more complex.     

Fractionated Reaction Time Responses to Auditory and Electrocutaneous Stimuli

Abstract

It is well documented that simple reaction time (RT) varies inversely with stimulus intensity, but there is disagreement as to which stimulus modality produces the fastest simple RT. An investigation was conducted to equate two stimulus modalities, auditory (A) and electrocutaneous (EC), using varying stimulus intensities in a simple RT protocol. A second investigation was then conducted to examine neuromotor characteristics of stimulus-evoked responses using previously equated A and EC stimuli of varying intensity from the first investigation. Results showed that RT, premotor time (PMT), and motor time (MT) were all inversely related to stimulus intensity, while maximum displacement (MAXD) was directly related to stimulus intensity, and movement time was not affected by stimulus intensity. We conclude that: (a) both central and peripheral components of RT are altered by varying stimulus intensities, and (b) rapid movements are enhanced by increasing stimulus intensity.     

Distribution of Practice in Motor Skill Acquisition: Different Effects for Discrete and Continuous Tasks

Abstract

Research on the benefits of distributed practice for the acquisition and retention of motor skills has a long history. The majority of this research has involved skill acquisition of continuous tasks. However, there is some evidence to suggest that distribution of practice effects are quite different for discrete tasks than for continuous tasks. In the present study, we used a single task, formed discrete and continuous versions of the task, and examined how acquisition and retention were affected by the length of inter-trial interval. The basic task was a movement timing task that involved either one timing estimate per trial (the “discrete” version) or twenty successive estimates per trial (the “continuous” version). Separate groups of subjects learned one version of the task under either distributed (25 s inter-trial intervals) or massed (0.5 s inter-trial intervals) practice conditions. Both massed and distributed retention trials were performed on the same version of the task according to a double transfer design. The results confirmed the apparent disparity: Acquisition and retention were facilitated by distributed practice on the continuous task, but by massed practice on the discrete task. These results were discussed in terms of the role of the inter-trial interval in discrete and continuous tasks.     

Precision of Knowledge of Results: Consideration of the Accuracy Requirements Imposed by the Task

Abstract

To investigate whether spatial assimilation effects are due to premovement control processes or postinitiation feedback processes, surface EMG recordings were made from two agonists and one antagonist during both single and dual movements involving the upper limb(s). In the single condition, subjects (N=7) made 25 Short (20°) and 25 Long (60°) reversal movements using levers in the sagittal plane, in 195 ms to reversal. In the dual condition, both Short and Long movements were performed simultaneously for 75 trials, the last 25 of which were without knowledge of results. Subjects overshot the Short target in the dual condition, showing spatial assimilation effects. Overshooting was associated with increased peak EMG in the initial (premovement) agonist burst, supporting the notion that spatial assimilation effects are modulated via premovement control processes.     

The continuous nature of timing reprogramming in an interceptive task

The time course of movement timing reprogramming was examined in a task requiring temporal coincidence of the conclusion of a forehand drive with the arrival of a moving luminous target at the end of an electronic trackway. The moving target departed from one end of the trackway at a constant velocity of 2?m ^. s^?1, and for a part of the trials its velocity was increased to 3?m ^. s^?1. Target velocity was modified at different moments during stimulus displacement, producing times-to-arrival after velocity increment (TAVIs) from 100 to 600?ms. The effect of specific practice on movement reprogramming was also examined. The results showed early adjustments to the action (TAVIs = 100?–?200?ms) that seemed to be stereotyped, while feedback-based corrections were implemented only at TAVIs of 300?ms or longer. Temporal accuracy was progressively increased as longer TAVIs were provided up to 600?ms. Skill training led to an overall increment of temporal accuracy, but no effect of specific practice was found. The results indicate that timing reprogramming in interceptive actions is a continuous process limited mainly by intrinsic factors: latency to initiate more effective adjustments to the action, and rate-of-movement timing reprogramming.     

A Test of Schmidt's Schema Theory of Discrete Motor Skill Learning

Abstract

Schmidt's (1975) schema theory was tested with subjects who had to emit a rapid aiming response while wearing prism glasses. The glasses enabled them to view the target, but not their responding limb or the outcome of the movement. The problem was to determine the effect of (a) training with variable target practice, and (b) experiencing visual displacement information of the target, prior to training, on performance in transfer to a novel target distance. A 2 × 2 (type of practice × displacement information) factorial design was used, in which four groups of 15 male college subjects performed 60 training trials with verbal knowledge of results. The groups with variable target practice had less error on initial transfer to the novel target and throughout transfer than the groups with nonvariable target practice. No evidence was found to indicate that rate of learning for a novel target distance during transfer in the absence of KR is a positive function of the variability of target practice in training. Nor was any effect found for experiencing visual displacement information on performance in transfer.     

The Effects of Age and Number of Demonstrations on Modeling of Form and Performance

Abstract

This study was designed to investigate the effects of age and number of demonstrations on both form (strategy employed) and physical performance on a Bachman ladder-balance task. College age (n = 60) and elementary age females (n = 60) were compared under four modeling conditions consisting of no, four, eight, and 12 demonstrations in an Age Group × Demonstration Group (2 × 4) MANOVA. Results indicated that college age students had higher performance and form scores than elementary age students. Only form differentiated the four demonstration groups. Participants receiving 12 demonstrations had higher form scores than the control participants. Form scores were analyzed in a discriminant function analysis to determine which of five form components differentiated the four demonstration groups. Results also revealed that climbing quickly was the component of form that differentiated the groups the most. It was concluded that matching form by the learner may be a more effective measure of modeling effects rather than inferring modeling from performance, especially in the initial stages of learning. In addition, it appears that the number of demonstrations needed to create modeling effects is task specific and dependent on the length of the practice period.