Power spectrum characteristics of sway position and velocity of the center of pressure during static upright posture for healthy people

This study assessed sex and individual differences in sway-position and velocity power spectra and reliability of power frequency with 30 health young people. The body sway for 1 min. was measured twice over a 1-min. rest. There were no significant sex differences in the spectra. Frequency bands with a large coefficient of variance over 10.0 appeared up to 0.6 Hz. 75% relative accumulated power frequency appeared at 1.10-1.23 Hz in the position and at 2.00-3.05 Hz in the velocity spectra. Most power was in the low frequency band (A and B frequency intervals) of the international standard. Relative accumulated power frequency of position and velocity power spectra was reasonably reliable. It may be necessary to establish a new evaluation frequency interval by direction of sway-position and velocity using relative accumulated power frequency for healthy people.     

Age-stage differences in body sway during a static upright posture based on sway factors and relative accumulation of power frequency

This study was done to examine age-stage (preschool children, young adults, and elderly people) differences in the center-of-pressure sway using body-sway factors (unit-time sway, front-back sway, left-right sway, and high frequency-band power), power-spectrum distribution, and relative accumulation of power frequency (25%, 50%, and 75% RAPF) of the center-of-pressure spectrum. The center-of-pressure movement for 1 min. was measured twice using Anima's stabilometer. Data-sampling frequency was set at 20 Hz. Significant age-stage differences were found for 3 factors except for left-right sway, which was larger for preschool children and elderly than for young adults. The power spectrum of body sway in any age-stage was noted mainly in low frequency bands. A marked age-stage difference was found at 75% RAPF. Body-sway characteristics in each age-stage differ, and differences of postural-sway frequency are marked in the low frequency bands.     

Characteristics of body excursion during a static upright posture in elderly people with central nervous system disorders and with other disorders from the viewpoint of body-excursion parameters

This study aimed to compare characteristics of body excursion of healthy elderly and elderly people with disorders. The participants were 38 healthy elderly who were at home (Healthy Elderly group) and 24 elderly people with disorders. The latter consisted of two groups: 12 in the Central Nervous System Disorders group with vestibular organ or central nervous system disorders, and 12 in the Other Disorders group with other system disorders. 34 parameters were selected from six domains: distance, distribution of amplitude, area, velocity, power spectrum, and vector. When compared with the Healthy Elderly group, the Central Nervous System Disorders group was judged abnormal on many parameters and showed large and quick body excursion characteristics, particularly in left-right excursion. The Other Disorders group showed different characteristics in the size of the left-right excursion and velocity of the front-back excursion. However, compared with the Central Nervous System Disorders group, very few people in the Other Disorders group were judged abnormal, and they showed slower velocity for front-back excursion.     

Effects of room tilting on body sway: Adaptation and strategies for maintaining a standing posture

The purpose of this study was to examine the effects of a tilting room on body sway across a series of trials. Sixteen subjects were instructed to maintain an upright position in the tilting room, and their body sway was measured by a force plate. After the experimental session, subjects were interviewed about awareness, strategies and impressions. The results indicated that the forward-tilting room induced forward body sway, as would a moving room. The center of gravity in the pre-tilting period in the first trial was significantly more forward than in the following trials. From the analysis of strategy, subjects were divided into two groups: maintaining-standing strategy group and other-strategies group. While subjects who used the maintaining-standing strategy swayed more in the first trial, they had significantly reduced their body sway compared with the other group by the ninth and tenth trials. Based on these results, the effects of a moving room for adult subjects as related to the context-dependent weighting of new inputs are discussed.     

Comparison of the body-sway characteristics of young adults compared to healthy elderly and elderly with equilibrium disorder

The study compared body-sway characteristics of 380 young adults, 342 generally healthy elderly without disequilibrium disorders, and a group of 33 elderly with disequilibrium disorders. Center of foot pressure (COP) was measured for 1 min. using an Anima's stabilometer G5500 with a data sampling frequency of 20 Hz. Four high reliability measures were used to evaluate body sway (unit time sway, front-back sway, and a left-right sway, and high frequency band power). Unit time sway, left-right sway, and high frequency band power were significantly larger for the group of elderly with disequilibrium disorders, and smaller for the healthy elderly people and young adults, in that order. Front-back sway was significantly larger in the elderly with disequilibrium disorders and healthy elderly than in young adults. The elderly with disequilibrium disorders had a larger and faster sway than young adults as well as the healthy elderly, particularly in the left-right direction. It appears aging was specifically associated with larger influence on the front-back sway.     

Influence of vision and static stretch of the calf muscles on postural sway during quiet standing

The purpose of this experimental study was to evaluate the effects of vision and stretching of the calf muscles on postural sway during quiet standing. Under pre-stretch conditions, participants stood on a force plate for 30s and the sway of the ground reaction force center of pressure was recorded. The following postural sway variables were calculated off-line: sweep speed, sway speed, standard deviation, maximal mediolateral range, maximal anteroposterior range, mean mediolateral position and mean anteroposterior position. For post-stretch conditions, participants stood quietly on a device that was utilized to impose a static 3 min ankle joint dorsiflexion stretch. Immediately thereafter, participants moved onto the force platform where postural sway parameters were again recorded. Randomized eyes-open and eyes-closed conditions were tested in both cases. Results showed that postural sway significantly increased due to stretch (sweep speed, sway speed, standard deviation, maximal anteroposterior range, mean anteroposterior position), as well as eye closure (sweep speed, sway speed, standard deviation, maximal mediolateral range, maximal anteroposterior range). The interaction between stretch and eye closure was also significant (sweep speed, sway speed, standard deviation, maximal mediolateral range), suggesting that there were only minor increases in postural sway after stretch under the eyes-open condition. It was suggested that stretching of the calf muscles has the effect of increasing postural sway, although this effect can be greatly compensated for when vision is included.     

Magnitude of force perception errors during static contractions of the knee extensors in healthy young and elderly individuals

The accuracy of force perception during muscular contraction has not been studied extensively, despite its importance in rehabilitation and training. The purpose of this study was to quantify the errors made by healthy young and elderly individuals in their perceptions of force produced at the knee. Four different tasks were used to evaluate the perception of force and the effect of a sensory-motor reference and simultaneous contraction on the accuracy of perception. The absolute errors were similar between groups, with values of 11.9% to 16.3%, depending on the task. The raw perception errors were greater for high levels of force (>50% of the maximal voluntary contraction, or MVC), indicating an overestimation of the forces produced for both groups. At 70% MVC, the sensory-motor reference reduced raw perception errors, and the simultaneous contraction improved the accuracy of force production. Healthy young and elderly individuals had about the same capacity to judge the muscular force of their knee extensors. Therapists involved in the training of active?elderly?individuals should be aware that the accuracy of force perception is not perfect and that these clients have the same ability as young individuals to perceive their knee extension strength.     

The effects of pain and a secondary task on postural sway during standing

BackgroundPain impairs available cognitive resources and somatosensory information, but its effects on postural control during standing are inconclusive. The aim of this study was to investigate whether postural sway is affected by the presence of pain and a secondary task during standing.MethodsSixteen healthy subjects stood as quiet as possible at a tandem stance for 30s on a force platform at different conditions regarding the presence of pain and a secondary task. Subjects received painful stimulations on the right upper arm or lower leg according to a relative pain threshold [pain 7 out 10 on a Visual Analog Scale (VAS) - 0 representing “no pain” and 10 “worst pain imaginable”] using a computer pressurized cuff. The secondary task consisted of pointing to a target using a head-mounted laser-pointer as visual feedback. Center of Pressure (COP) sway area, velocity, mean frequency and sample entropy were calculated from force platform measures.FindingsCompared to no painful condition, pain intensity (leg: VAS = 7; arm VAS = 7.4) increased following cuff pressure conditions (P < .01). Pain at the leg decreased COP area (P < .05), increased COP velocity (P < .05), mean frequency (P < .05) and sample entropy (P < .05) compared with baseline condition regardless the completion of the secondary task. During condition with pain at the leg, completion of the secondary task reduced COP velocity (P < .001) compared with condition without secondary task.InterpretationPain in the arm did not affect postural sway. Rather, postural adaptations seem dependent on the location of pain as pain in the lower leg affected postural sway. The completion of a secondary task affected postural sway measurements and reduced the effect of leg pain on postural sway. Future treatment interventions could benefit from dual-task paradigm during balance training aiming to improve postural control in patients suffering from chronic pain.     

Perception of weight-bearing distribution during sit-to-stand task in healthy young and elderly individuals

The first objective was to assess whether healthy individuals could accurately estimate their weight-bearing distribution in sit-to-stand transfers. The second was to evaluate the effect of age on weight-bearing perception. 16 young participants (11 women, 5 men; M age 29 yr., SD = 8.7) and 15 elderly participants (7 women, 8 men; M age 65 yr., SD = 3.8) were recruited. Verbal instructions and visual feedback referring to different percentages of weight-bearing distribution to execute were used to quantify weight-bearing perception in sit-to-stand tasks. For the feedback approach, the perception was assessed with a visual analog scale. For the verbal task, the weight-bearing distribution produced was assessed with force plates. Both young and elderly participants had good perception of weight-bearing distribution, with mean absolute errors of 6.4%. Moreover, their perceived and real weight-bearing distribution showed good agreement (ICC > or = .79).     

Height of chair seat and movement characteristics in sit-to-stand by young and elderly adults

The height of a chair seat affects the burden on the lower limbs during the sit-to-stand (STS). To develop an objective test to evaluate muscle function of the lower limbs using floor reaction force during a STS, the relationship between chair-seat height and the burden on the lower legs must be assessed. To examine the influence of the chair-seat height, floor reaction forces during a STS performed with 5 chair heights adjusted to each subject's lower leg length were compared. The force production and quickness of movement tended to decrease in the phases of trunk flexion and knee and hip joint extension when performing a STS from a lower chair, when the chair height differed by 20% (6.2 cm) from the lower leg length, and was marked when the difference between chair height and lower leg length became larger. In 52 elderly and 50 young adults, floor reaction forces during a STS performed from a chair of the same height as subjects' lower leg lengths were compared. Elderly persons were inferior in force production (strength) and quickness of movement, which decreased as elderly stood up from a chair of a lower height.     

Hemispheric lateralization of the EEG during wakefulness and REM sleep in young healthy adults

EEG recordings confirm hemispheric lateralization of brain activity during cognitive tasks. The aim of the present study was to investigate spontaneous EEG lateralization under two conditions, waking and REM sleep. Bilateral monopolar EEG was recorded in eight participants using a 12-electrode montage, before the night (5 min eyes closed) and during REM sleep. Spectral analysis (0.75-19.75 Hz) revealed left prefrontal lateralization on total spectrum amplitude power and right occipital lateralization in Delta activity during waking. In contrast, during REM sleep, right frontal lateralization in Theta and Beta activities and right lateralization in occipital Delta activity was observed. These results suggest that spontaneous EEG activities generated during waking and REM sleep are supported in part by a common thalamo-cortical neural network (right occipital Delta dominance) while additional, possibly neuro-cognitive factors modulate waking left prefrontal dominance and REM sleep right frontal dominance.     

Response inhibition and avoidance of virtual obstacles during gait in healthy young and older adults

Adjustments of preplanned steps are essential for fall avoidance and require response inhibition. Still, inhibition is rarely tested under conditions resembling daily living. We evaluated the ability of young and older adults to modify ongoing walking movements using a novel precision step inhibition (PSI) task combined with an auditory Stroop task.Healthy young (YA, n = 12) and older (OA, n = 12) adults performed the PSI task at 4 individualized difficulty levels, as a single and dual task (DT). Subjects walked on a treadmill by stepping on virtual stepping stones, unless these changed color during approach, forcing the subjects to avoid them. OA made more failures (40%) on the PSI task than YA (16%), but DT did not affect their performance. In combination with increased rates of omitted Stroop task responses, this indicates a “posture first” strategy. Yet, adding obstacles to the PSI task significantly deteriorated Stroop performance in both groups (the average Stroop composite score decreased by 13% in YA and 27% in OA). Largest deficit of OA was observed in rates of incorrect responses to incongruent Stroop stimuli (OA 35% and YA 12%), which require response inhibition. We concluded that the performance of OA suffered specifically when response inhibition was required.     

Effect of magnetic insoles on postural sway measures in men and women during a static balance test

Numerous anecdotal reports have suggested a growing public enthusiasm for magnetic devices for treatment of pain and various motor and sensory dysfunctions. Although the principles behind magnetic therapy are well documented, a complete technical explanation of whether static magnet application is effective is lacking due to a paucity of scientific research. In this study the effectiveness of magnetic insoles on postural sway measures during a single application were investigated. Twenty-eight adults (14 old, 14 young) were assessed on postural sway measures while performing a static two-legged stance test on a Kistler force platform under two treatment conditions (magnetic insoles, nonmagnetic insoles). Significant reductions in total sway area and lateral sway scores were obtained by the older adults while standing on the magnetic insoles. These preliminary results indicate that treatment of postural instability using magnetic insoles may be a viable alternative for older adults.     

Social anxiety mediates the effect of autism spectrum disorder characteristics on hostility in young adults

Problems with social anxiety are frequently reported in people with autism spectrum disorders (ASD). It is possible that social anxiety, when present, exacerbates the experience of hostility and other forms of aggression in relation to ASD symptoms. This study sought to determine if social anxiety symptoms mediate the relationship between features of ASD and feelings of hostility in young adults. Self-report measures of social anxiety, ASD, and facets of aggression were collected in a non-clinical sample (n = 618) of college students. Social anxiety was found to partially mediate the relationship between ASD features and self-reported hostility. There was also evidence for inconsistent mediation, such that social anxiety dampened the strength of the relationship between ASD symptoms and verbal and physical aggression. Findings highlight the potential influence of associated psychiatric symptoms in people with ASD. In addition, dimensional conceptualization of ASD symptoms, as opposed to a categorical approach solely, may be a useful approach to studying complex personality processes.     

Movement structure in young and elderly adults during goal-directed movements of the left and right arm

Elderly adults often exhibit performance deficits during goal-directed movements of the dominant arm compared with young adults. Recent studies involving hemispheric lateralization have provided evidence that the dominant and non-dominant hemisphere-arm systems are specialized for controlling different movement parameters and that hemispheric specialization may be reduced during normal aging. The purpose was to examine age-related differences in the movement structure for the dominant (right) and non-dominant (left) during goal-directed movements. Young and elderly adults performed 72 aiming movements as fast and as accurately as possible to visual targets with both arms. The findings suggest that previous research utilizing the dominant arm can be generalized to the non-dominant arm because performance was similar for the two arms. However, as expected, the elderly adults showed shorter relative primary submovement lengths and longer relative primary submovement durations, reaction times, movement durations, and normalized jerk scores compared to the young adults.     

Effects of visual center of pressure feedback on postural control in young and elderly healthy adults and in stroke patients

The goal of this study was to compare young and elderly healthy individuals and elderly stroke patients in their capacity to use visual CP feedback (VF) in controlling both quiet standing and weight shifting and to assess their sensory re-weighing when this VF is withdrawn. A total of 40 participants were involved in this study. Participants were asked to either quietly stand on a force platform for a period of 45 s with eyes open (EO), using visual feedback (VF) or without visual feedback (No VF) or to perform a dynamic weight shifting task while using VF or No VF. During the quiet standing trials with VF, only the young (YO) were able to decrease the amplitude and increase the frequency of their sway in either plane. Removal of the VF resulted in a 'destabilizing' effect in both healthy elderly (EL) and stroke patients (ST) in the sagittal plane. With regard to the dynamic task, both the YO and EL were generally more successful at weight shifting in terms of speed and control when compared to the ST. Yet, when VF was removed, only the YO were able to largely maintain speed and precision of control. Hence, providing or removing visual CP feedback during quiet standing or removing VF during visually controlled weight shifting can discriminate healthy young participants from healthy elderly, but does not clearly discriminate healthy elderly from stroke patients in the same age group. Results revealed that sagittal plane imbalance in healthy elderly and stroke patients may be largely due to the effects of aging, whereas frontal plane imbalance is much more specific for the postural problems associated with stroke.     

Comparison of Motionlogger Watch and Actiwatch actigraphs to polysomnography for sleep/wake estimation in healthy young adults

Sleep/wake identification and sleep parameter estimates from Motionlogger Watch and Actiwatch-64 actigraphs were compared to polysomnography (PSG). Following one night of baseline sleep, 29 volunteers remained awake for 36 h, followed by 11 h of recovery sleep in the laboratory. Two sets of analyses were performed: (1) epoch-by-epoch agreement and discriminability index (d') calculations, and (2) sleep parameter concordance with repeated measures ANOVAs. Sensitivity (sleep identification), specificity (wake detection), and overall agreement with PSG, as well as d', were higher for the Motionlogger than for Actiwatch. Relative to PSG, the Actiwatch-estimated total sleep time and sleep efficiency were underestimated and the number of awakenings was overestimated for baseline and recovery; sleep latency was underestimated on the baseline night. On the other hand, the Motionlogger-estimated total sleep time and sleep efficiency estimates were underestimated, and the sleep latency was overestimated on recovery, versus PSG. Despite these misestimations, it was concluded that the Motionlogger provided nominally better agreement with PSG, and that actigraphy generally constitutes a reasonably reliable tool for producing objective measurements of sleep/wake, but that users should remain mindful of its limitations.     

Personality and attitudinal correlates of healthy and unhealthy lifestyles in young adults

Abstract

The relationship between healthy lifestyle and personality and attitudinal variables was analyzed with data collected from 809 men and 996 women aged 18–30 years in England, Belgium, Finland and Norway as part of the European Health and Behaviour Survey. A health practices index was constructed on the basis of performance of sixteen behaviours including smoking, alcohol consumption, exercise, sleep time and a variety of dietary and preventive practices. Scores on the health practices index were higher in women than men, but in both sexes the index was normally distributed. Consistently healthy practices were positively correlated with extraversion and optimism, and negatively associated with neuroticism, psychoticism and chance locus of control beliefs. These effects were maintained after controlling for social desirability, but together accounted for only a modest proportion of the variance in the health practices index. The results are discussed in relation to the factors characterising health conscious and unhealthy lifestyles.     

Challenging horizontal movement of the body during sit-to-stand: impact on stability in the young and elderly

There are 3 significant challenges to sit-to-stand: (a) bringing the center of mass forward, (b) vertically raising the center of mass from the sitting to standing position, and (c) transition from a relatively large and stable base of support in sitting to a considerably smaller base of support when standing. The authors explored the challenges to stability control following sit-to-stand when the requirement for horizontal movement of the center of mass was influenced by foot position and their potential effect on the preceding phases of sit-to-stand. Eleven healthy young and 11 healthy elderly individuals performed the sit-to-stand with their feet further away and closer to the chair. Kinetic and kinematic data were recorded. Regardless of foot position, challenges in stability were greater in elderly participants than young participants despite their similar movement time and shear forces. The greater instability in elderly participants, despite their comparable movement characteristics, emphasizes the importance of stability control following sit-to-stand performance. For both young and elderly participants, the sit-to-stand duration and the shear forces were greater in the far condition. However, foot position did not affect the stability measures (i.e., duration of the stabilization phase and the total center of pressure path during the 1st second of the stabilization phase).     

Multiple stereotypes of elderly and young adults: a comparison of structure and evaluations

Following Schmidt and Boland's (1986) method, college student informants sorted a trait set into 1 or more groups with reference to elderly or young adults. Analysis of these data confirmed the existence of multiple stereotypes of both age groups but showed little similarity between stereotypes of the elderly and the young. Other informants made attitude, age, and typicality judgements of persons representing either the elderly or young adult stereotypes. Results showed that attitudes varied with the stereotype activated and were similar for analogous elderly and young adult stereotypes. Results also suggested that young adults do not view negative stereotypes as more typical of the elderly than positive ones; however, they believe the negative stereotypes are more characteristic of the old-old than are the positive and see positive stereotypes as more typical of young adults than negative ones.