Reliability of upper extremity kinematics while performing different tasks in individuals with stroke.

Assessments of upper extremity performance typically include qualitative rather than quantitative measures of functional ability. Kinematic analysis is an objective, discriminative measure that quantifies movement biomechanics; however, the use within the poststroke impaired upper extremity is not well established. The purpose of this study was to examine the reliability of upper extremity kinematics in 18 individuals with stroke and 9 healthy controls. Participants performed reaching and grasping tasks over 2 separate days and metrics included movement time, peak velocity, index of curvature, trunk displacement, maximum aperture, and percentage of the movement cycle where maximum aperture occurred. The results showed moderate to high intraclass correlation and low standard error of measurement values for most variables, demonstrating that kinematic analysis may be a feasible and useful tool to quantify upper extremity movement after stroke.

Implicit learning of a motor skill after mild and moderate stroke.

OBJECTIVE: To determine if adults in the subacute phase post moderate or mild stroke could learn a motor task under implicit practice conditions. DESIGN: Non-randomized, between-group design. SETTING: Subjects' homes. SUBJECTS: Sample of convenience of 15 adults with moderate stroke, 22 adults with mild stroke, and 32 age-matched controls. Stroke severity was determined using the Orpington Prognostic Scale. INTERVENTION: Practice of movements to target switches in two conditions, a repeated series and a random series. Practice was organized into a single session of six blocks of 80 trials such that blocks 1 and 2 were the random series, blocks 3 and 4 the repeated series, block 5 the random series, and block 6 the repeated series. Explicit knowledge of the two conditions was not provided. MAIN MEASURES: The mean response time and the coefficient of variation were calculated for each block for each group. RESULTS: Regardless of group, participants had a slower response time when practice was unexpectedly switched from the repeated to random condition. The response time and coefficient of variation for those with moderate stroke were persistently greater than those with mild stroke and controls, who were not different from each other. CONCLUSIONS: Implicit motor learning is preserved in adults with moderate stroke and may be a viable strategy for teaching motor skills in rehabilitation. The clinician should be aware that subjects with moderate stroke, even when performing with the less affected upper extremity, have significantly slower and more variable movements than those with mild stroke and controls.

Implicit learning of a perceptual-motor skill after stroke.

BACKGROUND AND PURPOSE: A motor skill can be learned implicitly, without awareness of what is being learned. The purpose of this study was to examine the ability of adults who had unilateral stroke to learn implicitly a perceptual-motor task. SUBJECTS: Subjects were 47 people who were poststroke and 36 control subjects. METHODS: Participants performed sequences of hand movements in response to target lights in 2 conditions: a patterned sequence and a random sequence. Participants were not given explicit knowledge of the presence of the 2 conditions. Those who had stroke performed with the upper-extremity ipsilateral to the lesion. RESULTS: Subjects who had stroke performed more slowly than control subjects. For both groups, times decreased with practice of the patterned sequence, increased with introduction of the random sequence, and decreased again with reintroduction of the patterned sequence. Group differences persisted in a retention test given the next day of the patterned sequence, and both groups showed decreased times over the course of the retention test. DISCUSSION AND CONCLUSION: People with stroke are able to learn a perceptual-motor task even without explicit instructions regarding the patterned sequence embedded in the task.

Posture effects on grip strength.

OBJECTIVE: To examine whether grip strengths were different when measured in supine and sitting positions. DESIGN: Comparison, convenience sample. SETTING: Community. PARTICIPANTS: Seventy-four healthy adult participants with no history of psychiatric or neurological dysfunction, or upper extremity orthopedic dysfunction after the age of 18. INTERVENTIONS: Participants performed grips with each hand while sitting and standing. Shoulder was adducted and extended, with the elbow flexed, and wrist and forearm in neutral. MAIN OUTCOME MEASURE: The mean of the three trials with each hand in each posture. RESULTS: Men were stronger (49kg) than women (29kg; p < .001). Right hands were stronger (41kg) than left (39kg; p < .001). However, grip strengths while sitting were equivalent to those tested while supine (p > .59). CONCLUSIONS: Using identical upper extremity positions, grip strength is equivalent when tested in the supine and sitting positions. Thus, when determining grip strength, grips measured while the subject is supine can be compared with norms collected while the subject is sitting, provided the upper extremity position is invariant.

How forearm position affects grip strength.

OBJECTIVE: Several studies have indicated that changing body positions results in altered grip strengths. Although one might expect that grip strength would be influenced by the position of the forearm during gripping due to the biomechanical properties of the forearm and hand muscles, no investigations of this variable have been undertaken. METHOD: This study examined the effect on grip strength of moving the forearm among supinated, neutral, and pronated positions while maintaining the standard position recommended by the American Society of Hand Therapists. The mean of three grip trials in each position was recorded for each of 106 subjects. RESULTS: Grips in forearm supination were the strongest, followed by grips in the neutral position. Grips in pronation were the weakest. CONCLUSIONS: The changes in grip strength observed with variations in forearm position further support the necessity of a standard position for testing grip strength. The knowledge of how changes in body position affect the strength of the grip can be used to design environments and tools to maximize biomechanical abilities.

Typicality effects in artificial categories: is there a hemisphere difference?

In category classification tasks, typicality effects are usually found: accuracy and reaction time depend upon distance from a prototype. In this study, subjects learned either verbal or nonverbal dot pattern categories, followed by a lateralized classification task. Comparable typicality effects were found in both reaction time and accuracy across visual fields for both verbal and nonverbal categories. Both hemispheres appeared to use a similarity-to-prototype matching strategy in classification. This indicates that merely having a verbal label does not differentiate classification in the two hemispheres.

What the passenger contributes to passenger comfort.

An individual's reaction to a vehicle environment depends not only on the physical inputs but also on the characteristics of the individual. Surveys of airline passengers were conducted on board regularly scheduled commuter flights. Sex of the respondent and attitude toward flying were found to have import nt influences on passenger comfort. Individual differences were also found regarding (1) perceptions of environmental variables, (2) the importance of factors as determinants of comfort, and (3) the ease of and frequency of performing activities in flight.

Models of human reaction to vehicle environments.

Models for predicting human comfort responses to environmental variables are presented for diverse vehicles. Air mode studies reveal that comfort is a function of vertical and transverse accelerations, noise levels and seat factors, as well as manoeuvre conditions. Comfort models for ground-based vehicles involve roll rates and noise levels.

Concorde: ride quality and passenger reactions.

On four Concorde flights, recordings of environmental characteristics during flight were made and questionnaires were distributed to passengers to assess their reactions during and 24 h after their flight. The Concorde users were mostly traveling for business reasons. Most respondents were flying the Concorde for the first time. Passengers were satisfied with the Concorde, found it comfortable, and were able to perform a variety of activities in flight. On the day after their flight, respondents felt good, rested, and active. They reported less jet lag as a result of their Concorde flight than they had previously experienced on other transatlantic flights. Most respondents are likely to use the Concorde again.

Recognition thresholds as a function of word length.

Several experiments investigated the effect of word length on recognition thresholds for both familiar English words and unfamiliar pseudowords, the thresholds measured both with and without a stimulus mask. For familiar English words, length had no effect either with or without a mask. For unfamiliar pseudowords, length had a dramatic effect both with and without a mask.

Ride Quality Evaluation II: Modelling of Airline Passenger Comfort.

Quantitative environmental and subjective data obtained aboard commercial airlines are used to model passenger reaction. Several models for comfort are compared. The manner in which the overall response to the flight environment depends on the time history is examined and the variability about the mean response discussed. The relationship to passenger satisfaction is presented giving a quantitative means of relating the physical environment to passenger acceptance. The proposed models give aircraft designers and operators a method by which they may seek to maximize passenger comfort and therefore satisfaction.