Effect of increased load on scapular kinematics during manual wheelchair propulsion in individuals with paraplegia and tetraplegia

Repetitive loading of the upper extremity musculature during activities like wheelchair propulsion can lead to fatigue of surrounding musculature causing irregular segment kinematics. The goal of this study was to determine the effect of increase in load on the kinematics of the scapula in users with paraplegia and tetraplegia. Data were collected on 18 participants (11 with paraplegia and 7 with tetraplegia) using an electromagnetic motion tracking system (100Hz) and force sensing pushrim (200Hz). The participants propelled under no load and loaded conditions at their customary propulsion velocity. On average a 60N increase in force was elicited with the experimental protocol. Users with tetraplegia showed significant increases (p<.05) in the rate of change of scapular angles in the upward/downward rotation and the retraction/protraction direction under the loaded conditions, whereas users with paraplegia only showed difference in the retraction/protraction rotation direction. Overall both user populations moved towards position of increased downward rotation, anterior tilt and protraction with increase in load hence increasing the risk of impingement. This experiment adds depth to our understanding of dynamic scapular kinematics during wheelchair propulsion under different loading conditions and differences in scapular control between users with paraplegia and tetraplegia.     

Three-dimensional kinematics of the scapula and trunk,and associated scapular muscle timing in individuals with stroke

Poor scapulothoracic control is a risk for developing shoulder pathology, but has received little attention so far in individuals with stroke (IwS). Trunk and scapular kinematics and surface muscle activity were measured in 15 healthy controls and 18 IwS during a low and high forward flexion (FF). Group-differences in trunk and scapular kinematics were assessed during low and high FF using a t-test (independent samples). Differences in muscle onset and offset time relative to movement start (both FF tasks) were determined using a mixed model taking into account the different groups and muscles. Recruitment patterns per group and task were described based on significant differences between muscles. In IwS, earlier lower trapezius and late infraspinatus offset were found during low FF, as well as a later onset and earlier offset of serratus anterior. For low FF, significantly more trunk axial rotation was found in IwS during both elevation and lowering. During high FF, IwS showed significantly less scapular posterior tilt during elevation and more scapular lateral rotation during lowering. IwS demonstrated adaptive muscle timing with earlier initiation and late inactivation of lower trapezius and infraspinatus, possibly to compensate for a late activation and early deactivation of the serratus anterior and to establish as such the correct pattern of scapulothoracic movement.     

Evaluation of arm dominance by using the mechanomyographic signal

The authors collected and compared mechanomyo-graphic (MMG) signal behavior from the biceps brachii of left and right arms of right-handed men (n = 19) and women (n = 20) who performed isometric contractions at 5 contraction levels. Mean frequency (MF) and RMS values were calculated from the MMG signals that arose from lateral oscillations of muscle fibers. Across genders and arms, RMS values increased with contraction level and MF values decreased with increase in muscle contraction. The authors found no significant difference in those parameters between dominant and nondominant arms. Therefore, summation of muscle twitches obtained from the MMG signal collected in biceps brachii muscle does not reveal any difference between dominant and nondominant arms.     

Three-dimensional angular kinematics of the lumbar spine and pelvis during running

The objective of this study were to: (i) describe the typical three-dimensional (3D) angular kinematics of the lumbar spine and pelvis during running and; (ii) assess whether the movements of the lumbar spine and pelvis during running are coordinated. A cohort of 20 non-injured male runners who usually ran >20 km/week were voluntarily recruited. All trials were conducted on a treadmill at a running speed of 4.0 m/second. Reflective markers were placed over anatomical landmarks of the thoraco-lumbar spine and pelvis. Data were captured using a VICON motion analysis system. The lumbar spine and pelvis both displayed complex 3D angular kinematic patterns during running. High correlations were found for the comparisons of flexion-extension of the lumbar spine with anterior-posterior tilt of the pelvis (r=-0.84) and lateral bend of the lumbar spine with obliquity of the pelvis (r=-0.75). However, a poor correlation was found for the comparison of axial rotation of the lumbar spine with axial rotation of the pelvis (r=0.37). A phase difference of 21% of the running cycle was evident between axial rotation of the lumbar spine and pelvis. The identified coordinated kinematic patterns of the lumbar spine and pelvis during running serve as a basis for future investigations exploring the relationship between atypical kinematic patterns and injury.     

Gender differences in the variability of lower extremity kinematics during treadmill locomotion

The authors examined whether there were gender differences in the variability of basic gait parameters (stride length, stride time) and 3-dimensional (3D) rotations of the hip, knee, and ankle joints during treadmill locomotion of 18 men and 15 women at 4 different gait speeds (walking at 5 km/hr, running at 8, 10, and 12 km/hr). The authors used 2-way analyses of variance to assess the data. No gender differences in the mean values or variability of basic gait parameters were detected. However, the women exhibited lower variability than did the men for 6 individual joint rotations: (a) transverse plane rotations of the ankle joint at 8, 10, and 12 km/hr, (b) transverse plane rotations of the hip and knee joints at 12 km/hr, and (c) sagittal plane rotations of the ankle joint at 12 km/hr. When collapsed across all 3D lower extremity rotations, the data showed that the women had lower variability than did the men at 12 km/hr. Reduced variability may result in more localized mechanical stress on anatomical structures and could therefore be a risk factor for injury in women at high gait speeds. The results also suggested that gender differences in variability may not be consistent across different levels of the motor system.     

Measuring perceptual centers using the phase correction response

The perceptual center (P-center) is fundamental to the timing of heterogeneous event sequences, including music and speech. Unfortunately, there is currently no comprehensive and reliable model of P-centers in acoustic events, so P-centers must instead be measured empirically. This study reviews existing measurement methods and evaluates two methods in detail-the rhythm adjustment method and a new method based on the phase correction response (PCR) in a synchronous tapping task. The two methods yielded consistent P-center estimates and showed no evidence of P-center context dependence. The PCR method appears promising because it is accurate and efficient and does not require explicit perceptual judgments. As a secondary result, the magnitude of the PCR is shown to vary systematically with the onset complexity of speech sounds, which presumably reflects the perceived clarity of a sound's P-center.     

Measuring evaluative conditioning using the Implicit Association Test

When a neutral stimulus is paired with a stimulus that has strong affective properties, these properties often appear to be transferred to the neutral stimulus. This learning has been termed evaluative conditioning. In two experiments, participants first learned the ‘meanings’ of four non-words. Two of these meanings were affectively positive, and two were affectively negative. Transfer of affect was measured in the Implicit Association Test (IAT). In the IAT, a participant’s affective response to an item is inferred from his or her ability to categorise that item with other pleasant and unpleasant stimuli. An item easily categorised with other liked stimuli is deemed to be liked itself. In both experiments, evidence for transfer of affect was observed in the IAT. Thus, non-words given pleasant meanings in training (evaluative conditioning) were more easily categorised with pleasant than unpleasant personality characteristics, compared to non-words given unpleasant meanings. The results suggest that the IAT is a useful way to test for evaluative conditioning. It is both sensitive to the transfer of affective properties from one stimulus to another, and, because affect is measured indirectly, the results are unlikely to be due to the demand characteristics of the experiment.     

Toy-oriented changes in hand and joint kinematics during the emergence of purposeful reaching

Infants first consistently reach for objects between 3 and 5 months of age. In the months before reaching, infants produce a variety of arm movements. The relationship between these early arm movements and the emergence of purposeful reaching is still unclear. The purpose of the present study was to determine how groups of non-reaching, nearly reaching, and newly reaching infants changed the kinematics of their spontaneous arm movements in the presence of a toy. Five infants in each of these groups were observed with a high-speed motion capture system during trials with and without a toy present. Kinematic analyses examined 3D hand, shoulder, and elbow motions. Our results suggest that with a toy present, non-reachers altered their movement quantity whereas near- and new-reachers altered their movement quality through spatio-temporal dissociation and reorientation of the arm. When comparing the changes across groups we observed three preliminary patterns of toy-oriented changes. Our results join other studies to strengthen the relationship between early arm movements and purposeful reaching. Future longitudinal studies are now required to begin to fully understand the complex process by which infants adapt their early arm movements for purposeful behaviors.     

Multi-segmental thoracic spine kinematics measured dynamically in the young and elderly during flexion

In contrast to the cervical and lumbar region, the normal kinematics of the thoracic spine have not been thoroughly investigated. The aim of this study was to characterize normal multi-segmental continuous motion of the whole thoracolumbar spine, during a flexion maneuver, in young and elderly subjects. Forty-two healthy volunteers were analyzed: 21 young (age = 27.00 ± 3.96) and 21 elderly (age = 70.1 ± 3.85). Spinal motion was recorded with a motion-capture system and analyzed using a 3rd order polynomial function to approximate spinal curvature throughout the motion sequence. The average motion profiles of the two age groups were characterized. Flexion timing of the thoracic region of the spine, as compared to the lumbar spine and hips, was found to be different in the two age groups (p = 0.011): a delayed/sequential motion type was observed in most of the young, whereas mostly a simultaneous motion pattern was observed in the elderly subjects. A similar trend was observed in flexion of the lower thoracic segments (p = 0.017). Differences between age groups were also found for regional and segmental displacements and velocities. The reported characterization of the thoracic spine kinematics may in the future support identification of abnormal movement or be used to improve biomechanical models of the spine.     

Measuring the time course of selection during visual search

In visual search tasks, observers can guide their attention towards items in the visual field that share features with the target item. In this series of studies, we examined the time course of guidance toward a subset of items that have the same color as the target item. Landolt Cs were placed on 16 colored disks. Fifteen distractor Cs had gaps facing up or down while one target C had a gap facing left or right. Observers searched for the target C and reported which side contained the gap as quickly as possible. In the absence of other information, observers must search at random through the Cs. However, during the trial, the disks changed colors. Twelve disks were now of one color and four disks were of another color. Observers knew that the target C would always be in the smaller color set. The experimental question was how quickly observers could guide their attention to the smaller color set. Results indicate that observers could not make instantaneous use of color information to guide the search, even when they knew which two colors would be appearing on every trial. In each study, it took participants 200–300 ms to fully utilize the color information once presented. Control studies replicated the finding with more saturated colors and with colored C stimuli (rather than Cs on colored disks). We conclude that segregation of a display by color for the purposes of guidance takes 200–300 ms to fully develop.     

In-shoe multi-segment foot kinematics of children during the propulsive phase of walking and running

Certain styles of children’s shoes reduce 1st metatarsophalangeal joint (MTPJ) and midfoot motion during propulsion of walking. However, no studies have investigated if the splinting effect of shoes on children’s 1st MTPJ and midfoot motion occurs during running. This study investigated the effect of sports shoes on multi-segment foot kinematics of children during propulsion of walking and running. Twenty children walked and ran at a self-selected velocity while barefoot and shod in a random order. Reflective markers were used to quantify sagittal plane motion of the 1st MTPJ and three-dimensional motion of the midfoot and ankle. Gait velocity increased during shod walking and running and was considered a covariate in the statistical analysis. Shoes reduced 1st MTPJ motion during propulsion of walking from 36.0° to 10.7° and during running from 31.5° to 12.6°. Midfoot sagittal plane motion during propulsion reduced from 22.5° to 6.2° during walking and from 27.4° to 9.6° during running. Sagittal plane ankle motion during propulsion increased during shod running from 26.7° to 34.1°. During propulsion of walking and running, children’s sports shoes have a splinting effect on 1st MTPJ and midfoot motion which is partially compensated by an increase in ankle plantarflexion during running.     

Rapid acceleration of the lower arm correlates with agonist EMGs during the initial phase

Fifty-eight healthy subjects made rapid elbow extensions to a target over 54 degrees. Angular acceleration was measured and surface electromyograms (EMGs) were recorded from the antagonistic muscles using monopolar rather than bipolar electrode configurations. Marked individual differences were found in the peak value of the first derivative of acceleration (dAcc/dt_Pk). The dAcc/dt_Pk correlated with both quantitative and qualitative properties of the agonist EMGs, but not with those of the antagonist EMG. The agonist EMGs, integrated until the moment of dAcc/dt_Pk, were positively correlated with dAcc/dt_Pk. The interval between EMG onset and EMG peak decreased with increasing dAcc/dt_Pk. The duration of the initial negative phase in the EMGs, which was considered to index the time required to recruit high-threshold MUs, decreased with increasing dAcc/dt_Pk. The results indicate that the ability to rapidly accelerate the lower arm varies across subjects, probably due in part to individual differences in the neural capacity to drive the agonists.     

Measuring emotions during epistemic activities: the Epistemically-Related Emotion Scales

Measurement instruments assessing multiple emotions during epistemic activities are largely lacking. We describe the construction and validation of the Epistemically-Related Emotion Scales, which measure surprise, curiosity, enjoyment, confusion, anxiety, frustration, and boredom occurring during epistemic cognitive activities. The instrument was tested in a multinational study of emotions during learning from conflicting texts (N?=?438 university students from the United States, Canada, and Germany). The findings document the reliability, internal validity, and external validity of the instrument. A seven-factor model best fit the data, suggesting that epistemically-related emotions should be conceptualised in terms of discrete emotion categories, and the scales showed metric invariance across the North American and German samples. Furthermore, emotion scores changed over time as a function of conflicting task information and related significantly to perceived task value and use of cognitive and metacognitive learning strategies.     

An improved energy efficient cluster head selection protocol using the double cluster heads and data fusion methods for IoT applications

The more energy consumption is the major issue for wireless sensor network. In wireless sensor network (WSN), sensor nodes are fixed in various routing algorithms. In the same networks, mobile sensor and fixed sensor nodes are combine and its used in few applications. The function is corruption while mobility was achieved, since these nodes have minimum battery power, lower range of communication and a lessor amount of memory. To overcome this issue, Improved Energy Efficient Cluster Head Selection protocol (IEECHS-WSN) is proposed, in these technique is used to transfer the received information by using energy efficient routing protocol. In the CH election method, two cluster heads are selected in a separated cluster and its work in various functions, this can be prolong the network lifetime and decrease the energy consumption of IoT applications. Proposed technique is described on clustering of dual CHs in the method of data fusion for data entropy. This information entropy is used for fusion and classification, the result of fusion and classification are accurate and efficient for data transmission. Our proposed IEECHS protocol has better throughput, lifetime of network and energy consumption compared than the existing technique.     

Measuring reaction time with millisecond accuracy using the TRS-80 microcomputer

A machine language subroutine is proposed for measuring reaction time with millisecond accuracy using the TRS-80 microcomputer. This timer is accurate to 1 msec in the first 30,000 msec and to 5 msec in the first 65,000 msec (1 part in 10,000).     

Measuring facial identity and emotion integration using the redundancy gain paradigm

Early theories on face perception posit that invariant (i.e., identity) and changeable (i.e., expression) facial aspects are processed separately. However, many researchers have countered the hypothesis of parallel processes with findings of interactions between identity and emotion perception. The majority of tasks measuring interactions between identity and emotion employ a selective attention design, in which participants are instructed to attend to one dimension (e.g., identity) while the other dimension varies orthogonally (e.g., emotion), but is task irrelevant. Recently, a divided attention design (i.e., the redundancy gain paradigm) in which both identity and emotion are task relevant was employed to assess the interaction between identity and emotion. A redundancy gain is calculated by a drop in reaction time in trials in which a target from both dimensions is present in the stimulus face (e.g., “sad Person A”), compared with trials with only a single target present (e.g., “sad” or “Person A”). Redundancy gains are hypothesized to point to an interactive activation of both dimensions, and as such, could complement designs adopting a selective attention task. The initial aim of the current study was to reproduce the earlier findings with this paradigm on identity and emotion perception (Yankouskaya, Booth, & Humphreys, Attention, Perception, & Psychophysics, 74(8), 1692–1711, 2012), but our study failed to replicate the results. In a series of subtasks, multiple aspects of the design were manipulated separately in our goal to shed light on the factors that influence the redundancy gain effect in faces. A redundancy gain was eventually obtained after controlling for contingencies and stimulus presentation time.     

Effects of varying load conditions on the organization of postural adjustments during voluntary arm flexion

One purpose of the experiments reported here was to further clarify the effect of varying loads on postural adjustments. Another was to reevaluate whether or not the timing of electromyographic (EMG) activity in the postural muscle is preprogrammed. To accomplish these goals, we compared the effect of the presence or absence of prior knowledge of a load on the timing of EMG activity in the postural muscle (biceps femoris [BF]) with that in the focal muscle (anterior deltoid [AD]). Although the sequence of EMG activation was similar under conditions with and without a load, the timing of postural EMG activities (BFi, ipsilateral BF; BFc, contralateral BF) in associated postural adjustments was dependent on the force of arm movement, and the latencies of postural EMG activities (BFi-BFc) were dependent on the speed of arm movement. This indicates that EMG changes in the upper (focal muscle) and lower limbs (postural muscle) were triggered by different motor programs. Moreover, similar EMG activities were observed in postural muscles when the subject had advance knowledge of the presence or the absence of a load. Thus, this suggests that BFi may be centrally preprogrammed (anticipatory regulation) and BFc may be feedback regulated. Furthermore, environmental information may be a critical source of influence on those postural responses.     

Measuring self-esteem using the implicit association test: the role of the other

In two experiments, the use of a self-other Implicit Association Test (IAT) as a measure of implicit self-esteem was examined. In Study 1, participants completed two self-other IATs: one in which the other was unspecified and one in which the other was specified to be a close friend. Esteem-IAT scores were significantly higher for the unspecified other-IAT (d = .82), indicating that the content of the other has a considerable influence on the over-all esteem-IAT scores. Study 2 provided a conceptual replication of these results and provided some initial evidence that the valence of an unspecified other is negative. Across both studies, the nature of the mental representation of the self, as measured by an esteem-IAT, changed as a function of the mental representation of the other. The crucial role of the other-associations in the esteem-IAT calls into question its use and interpretation as a measure of self-esteem.