The influence of moving auditory stimuli on standing balance in healthy young adults and the elderly

The maintenance of postural balance depends on effective and efficient feedback from various sensory inputs. The importance of auditory inputs in this respect is not, as yet, fully understood. The purpose of this study was to analyse how the moving auditory stimuli could affect the standing balance in healthy adults of different ages. The participants of the study were 12 healthy volunteers, who were divided into two age categories: the young group (mean = 21.9 years) and the elderly group (mean = 68.9 years). The instrument used for evaluation of standing balance was a force plate for measuring body sway parameters. The toe pressure was measured using the F-scan Tactile Sensor System. The moving auditory stimulus produced a white-noise sound and binaural cue using the Beachtron Affordable 3D Audio system. The moving auditory stimulus conditions were employed by having the sound come from the right to left or vice versa at the height of the participant's ears. Participants were asked to stand on the force plate in the Romberg position for 20 s with either eyes opened or eyes closed for analysing the effect of visual input. Simultaneously, all participants tried to remain in the standing position with and without auditory stimulation that the participants heard from the headphone. In addition, the variables of body sway were measured under four conditions for analysing the effect of decreased tactile sensation of toes and feet soles: standing on the normal surface (NS) or soft surface (SS) with and without auditory stimulation. The participants were asked to stand in a total of eight conditions. The results showed that the lateral body sway of the elderly group was more influenced than that of the young group by the lateral moving auditory stimulation. The analysis of toe pressure indicated that all participants used their left feet more than their right feet to maintain balance. Moreover, the elderly had the tendency to be stabilized mainly by use of their heels. The young group were mainly stabilized by the toes of their feet. The results suggest that the elderly may need a more appropriate stimulus of tactile and auditory sense as a feedback system than the young for maintaining and control of their standing postures.     

The effect of occupational whole-body vibration on standing balance: A systematic review

Adverse health effects from exposure to occupational whole-body vibration (WBV) are common among drivers. In particular some researchers consider that there is kinaesthetic and balance disturbance from WBV exposure in the workplace and this might be one of the aetiological factors responsible for occupational low back pain in drivers. The purpose of this study was to undertake a critical review of the literature to determine whether exposure to seated occupational WBV can affect standing balance performance in an actual or simulated occupational environment. Specific keywords and MeSH terms for three major areas included WBV, balance and occupation. These were used to conduct a systematic search of the following databases; PubMed, EMBASE (Ovid), Medline (Ovid), CINAHL (EBSCO), Academic Search Complete (ASC), AMED, Scopus, Web of Science, Science Direct, Proquest, Cochrane library(OVID), IEEExplore and ProQuest Dissertations and thesis, Google Scholar, WorldCat and related conference proceedings. Five articles met the inclusion criteria and were assessed for quality. Two were field studies conducted on actual vehicles (a long haul freight truck and a bulldozer), while the other three were laboratory studies simulating the characteristics of the following vehicles; long-haul-dump vehicle, underground mine shuttle car, and helicopter. The systematic review scored the methodological quality of the included articles with an average and standard deviation of 76 ±12.3% (range 59- 93%) indicative of high quality. Three of the five studies (two field and one laboratory) found evidence for seated WBV decreasing standing balance performance while two laboratory studies did not find such effects. Thus there is modest evidence to suggest there is a decrease in standing balance performance following exposure to seated occupational WBV.

Relevance to industry

This systematic review suggests that balance deficits may exist immediately following exposure to occupational seated WBV and may predispose driver/operator to low back injury during manual material handling tasks immediately post driving.     

The influence of arm position on the pinch grip strength of female dentists in standing and sitting positions

The objective of this study was to measure and compare hand pinch grip forces in standing and sitting postures for a group of 77 healthy female dentists of 25 to 55 years old. The equipment used consisted of a gripping device with strain gauges, a measuring device and a printer. The results can be described as follows. With respect to absolute values the hand pinch forces are higher when the subject is standing with her arm supported, than when she is sitting. In the standing position the measured forces were maximum when the forearm was at 60 degrees angle towards the frontal position, while in the sitting position the pinch grip forces were maximum with the forearm vertical (90 degrees ) with respect to the frontal position. The above data can be used to design the dentist's working area.     

The influence of a seated break on prolonged standing induced low back pain development

With the recent attention to ‘sitting disease’, health practitioners and scientists are promoting standing in the workplace to decrease sedentary time, despite a high prevalence of low back pain (LBP) development during prolonged standing. The purpose of this study was to assess how a seated break inserted between bouts of prolonged standing would influence LBP development, posture and movement. A total of 20 participants stood for 45 minutes, sat for 15 minutes and repeated this sequence while lumbar and thoracic angles were measured, and LBP visual analogue scale reports were taken. Of the sample, 55% participants reported LBP in standing. A stand to sit ratio of 3:1 did not provide lasting recovery of LBP from standing and pain developers utilised a limited range of their lumbar spine angle and increased thoracic extension, resulting in static postures that caused tissue aggravation that was not resolved after 15 minutes of sitting. Prolonged standing in the workplace has the potential to result in LBP for some workers and alternate ways to reduce sedentary time should be investigated.     

Factors affecting stepladder stability during a lateral weight transfer: a study in healthy young adults

A fall from a stepladder is often initiated by a loss of lateral stability. An inverted pendulum model of the human, validated by experiment, was used to determine the feasible range of whole-body center of mass (COM) states for which weight can be transferred laterally on a ladder tread without a ladder rail losing contact with the ground ("no lift-off" stability region). The results show that the size of the feasible no lift-off region was inversely proportional to the height of the tread above the ground, the distance of the stance foot from the ipsilateral rail, and lateral ground inclination angle. For given initial COM kinematics on a tread height equal to 40% human body height, a stance-foot location equal to one-eighth tread width and a 3.5 degrees ground inclination had approximately equivalent effects on the no lift-off region size. Ladder stability was three times more sensitive to tread height than to foot location. Laterally-exerted impulsive hand-tool forces should generally be limited to 8% body weight. These findings can lead to improved ladder designs and safety instructions for stepladder users.     

Effects of common working postures on balance control during the stabilisation phase of transitioning to standing

Standing after maintaining working postures may result in imbalance and could elicit a fall. The objective of this study was to assess the magnitude of this imbalance. Forty-five male participants completed three replications of conditions created by four static postures and three durations within posture. Participants transitioned to quiet standing at a self-selected pace. Body segment location and displacement of the centre of pressure (COP) were recorded using a motion capture system and two forceplates, respectively. Balance control measures were calculated during the stabilisation phase. All balance control measures were significantly affected by static posture but not duration within posture. Bending over at waist generally caused the smallest changes in balance control measures, whereas the reclined kneeling posture resulted in the largest. Findings may lead to recommendations for redesign of tasks to reduce the use of certain working postures, particularly in high-risk environments such as construction. STATEMENT OF RELEVANCE: Task performance on the jobsite often requires individuals to maintain non-erect postures. This study suggests that the working posture chosen affects stabilisation during a transition to a standing position. Bending at the waist or squatting seems to have less of an affect on balance control measures, whereas both types of kneeling postures evaluated resulted in greater imbalance.     

Falls in the healthy elderly: predisposing causes

One hundred healthy men and women aged 65-85 took part in a prospective study. They were clinically examined and underwent laboratory tests of gait, balance and reaction time at the start of an observation year.

All falls occurring in that year were analysed in detail. Three-quarters of them were trips or slips; however, ten personal factors were identified which, if present, increased the likelihood of a fall occurring. These were: disturbance of gait following a rest period accompanied by a lighting change (in persons aged 70 and over); an absent or abnormal plantar reflex; failure to wear prescribed spectacles; the presence of anxiety/depression, of a foot problem, or of two or more self-perceived limitations on mobility; a history of former wearing of high heels; a sustained drop in pulse pressure 5 min after cessation of a rest period; restricted neck movements; and the presence of an inverse Romberg ratio.

The number of circumstantial and personal factors contributing to the falls varied between three and twelve.     

Effects of high heeled shoes wearing experience and heel height on human standing balance and functional mobility

This study aimed to examine the effects of high heeled shoes (HHS) wearing experience and heel height on human standing balance and functional mobility. Thirty young and healthy females (ten experienced and twenty inexperienced HHS wearers) participated in a series of balance tests when they wore shoes of four different heel heights: 1 cm (flat), 4 cm (low), 7 cm (medium) and 10 cm (high). Experimental results show that regardless of the wearing experience, the heel elevation induces more effort from lower limb muscles (particularly calf muscles) and results in worse functional mobility starting at 7 cm heel height. While the heel height increased to 10 cm, the standing balance also becomes worse. Experienced HHS wearers do not show significantly better overall performance on standing balance and functional mobility than inexperienced controls, even though they have better directional control (76.8% vs. 74.4%) and larger maximum excursion (93.3% vs. 89.7%). To maintain standing balance, experienced wearers exert less effort on tibialis anterior, vastus lateralis and erector spinae muscles at the cost of more intensive effort from gastrocnemius medialis muscle.     

Control of standing balance while using constructions stilts: comparison of expert and novice users

This study examined the control of standing balance while wearing construction stilts. Motion capture data were collected from nine expert stilt users and nine novices. Three standing conditions were analysed: ground, 60 cm stilts and an elevated platform. Each task was also performed with the head extended as a vestibular perturbation. Both expert and novice groups exhibited lower displacement of the whole body centre of mass and centre of pressure on construction stilts. Differences between the groups were only noted in the elevated condition with no stilts, where the expert group had lower levels of medial–lateral displacement of the centre of pressure. The postural manipulation revealed that the expert group had superior balance to the novice group. Conditions where stilts were worn showed lower levels of correspondence to the inverted pendulum model. Under normal conditions, both expert and novice groups were able to control their balance while wearing construction stilts.     

Real time implementation of CTRNN and BPTT algorithm to learn on-line biped robot balance: Experiments on the standing posture

This paper describes experimental results regarding the real time implementation of continuous time recurrent neural networks (CTRNN) and the dynamic back-propagation through time (BPTT) algorithm for the on-line learning control laws. Experiments are carried out to control the balance of a biped robot prototype in its standing posture. The neural controller is trained to compensate for external perturbations by controlling the torso’s joint motions. Algorithms are embedded in the real time electronic unit of the robot. On-line learning implementations are presented in detail. The results on learning behavior and control performance demonstrate the strength and the efficiency of the proposed approach.     

Ranges of dynamic motion of the wrist in healthy young and middle-aged men

The difference in the range of dynamic motion of the wrist between young and middle-aged men was studied. To analyse wrist function easily, a new quantitative evaluation technique for wrist circumduction using a biaxial flexible electrogoniometer was introduced. A phase plane was made from two-channel signals of the electrogoniometer, and the ‘ROM (range of motion) Index’ for wrist circumduction was defined. Twelve healthy young men (age 19-31 years) and twelve healthy middle-aged men (age 45-63 years) were studied. Under forearm fixed conditions, there was no difference of the ROM Index between the two age groups. A significant decrease of the ROM Index in the middle-aged group was found in the non-dominant wrists without forearm fixation. The four quadrantal analysis of wrist circumduction clarified that this difference appeared especially in the radiodorsal direction. These results suggest that in the middle-aged men, the motor function involving the radiocarpal and midcarpal joints does not decrease, but that for the proximal and distal radioulnar joints in the non-dominant side drops.     

Computational attention model for children,adults and the elderly

Multimedia Tools and Applications - Computational models of saliency estimation have been studied in a wide range of research fields, including visual perception, image processing, computer vision,...     

#Gettinghealthy: The perceived influence of social media on young adult health behaviors

Young adults (18–25 years old) spend a majority of their waking hours with technology and young adulthood is an important developmental time period for establishing lasting health behaviors. Considering the relevance of technology and health during young adulthood the current study explored young adults (N = 34) perceptions of social media’s (e.g., social networking) influence on their health behaviors (i.e., diet and exercise) using a social ecological framework. Data was collected through eight focus groups and four individual interviews. Three themes were identified through phenomenological qualitative analysis. Young adults perceived that technology could be both a barrier and a motivator for exercise. Social media was also credited with expanding food choices through creating access to a variety of recipes, providing a venue for showcasing the food young adults eat or prepare, and distracting young adults from making positive food choices. Participants also reported that it is common to post statuses or pictures relating to exercise practices on social media during young adulthood. Young adults indicated that these posts could be inspirational or misused, depending on the context. Results are discussed in terms of theory and preliminary implications.     

Perceiving affordances in virtual reality: influence of person and environmental properties in perception of standing on virtual grounds

We evaluated the perception of affordances in virtual environments (VE). In our work, we considered the affordances for standing on a virtual slanted surface. Participants were asked to judge whether a virtual slanted surface supported upright stance. The objective was to evaluate whether this perception was possible in virtual reality (VR) and comparable to previous works conducted in real environments. We found that the perception of affordances for standing on a slanted surface in virtual reality is possible and comparable (with an underestimation) to previous studies conducted in real environments. We also found that participants were able to extract and to use virtual information about friction in order to judge whether a slanted surface supported an upright stance. Finally, results revealed that the person’s position on the slanted surface is involved in the perception of affordances for standing on virtual grounds. Taken together, our results show quantitatively that the perception of affordances can be effective in virtual environments and influenced by both environmental and person properties. Such a perceptual evaluation of affordances in VR could guide VE designers to improve their designs and to better understand the effect of these designs on VE users.     

Ranges of dynamic motion of the wrist in healthy young and middle-aged men.

The difference in the range of dynamic motion of the wrist between young and middle-aged men was studied. To analyse wrist function easily, a new quantitative evaluation technique for wrist circumduction using a biaxial flexible electrogoniometer was introduced. A phase plane was made from two-channel signals of the electrogoniometer, and the 'ROM (range of motion) Index' for wrist circumduction was defined. Twelve healthy young men (age 19-31 years) and twelve healthy middle-aged men (age 45-63 years) were studied. Under forearm fixed conditions, there was no difference of the ROM Index between the two age groups. A significant decrease of the ROM Index in the middle-aged group was found in the non-dominant wrists without forearm fixation. The four quadrantal analysis of wrist circumduction clarified that this difference appeared especially in the radiodorsal direction. These results suggest that in the middle-aged men, the motor function involving the radiocarpal and midcarpal joints does not decrease, but that for the proximal and distal radioulnar joints in the non-dominant side drops.     

A comparative investigation of the influence of certain arm positions on hand pinch grips in the standing and sitting positions of dentists

Hand pinch grips in the standing and sitting positions on a group of 46 healthy males of 20 to 26 years old were measured. The results were as follows: 1. Hand pinch grip forces are higher when the subject is standing than when he is sitting. 2. Hand pinch grip forces, depending on the position of the arm in the working space, are higher when the arm is supported than the corresponding forces of the unsupported arm. 3. There is an effect due to the position of the arm in relation to the frontal position of the subject's thorax. In the standing position, the forces are maximum when the forearm has a 60 degrees angle towards the frontal position, while in the sitting position pinch grip forces are maximum when the forearm is perpendicular (90 degrees ) to the frontal position. 4. A handle which permits all fingers to be spread in a pinch grip is capable of having an applied force 50% greater than if the thumb and either forefinger or middlefinger grips the handle. In such a handle each finger is required to apply less force to contribute to the total needed for the task, and therefore there is a diminished likelihood of the onset of fatigue.     

Trends in finger pinch strength in children, adults, and the elderly

This study explores empirical relationships among different types of pinches in three age groups. Peak maximum voluntary forces of several pinches--lateral, chuck, and pulp pinches with digits 2, 3, 4, and 5-were tested in 182 subjects comprising 62 children (5-12 years), 70 adults (18-40 years), and 50 elderly (60-89 years). Analysis of the forces indicated four groups of strength magnitude: (1) lateral and chuck, (2) pulp 2 and 3, (3) pulp 4, and (4) pulp 5, in that order; the strength of each type of pinch bears a definite quantitative relationship to every other type, regardless of age group or gender. The female-to-male strength ratio was greatest in children (89%) and least in adults (69%). Comparison with other pinch strength studies established that although force magnitudes may be strongly influenced by specific experimental conditions, empirical relationships among different pinch forces are fairly stable and predictable.     

Estimating spatio-temporal receptive fields of auditory and visual neurons from their responses to natural stimuli

We present a generalized reverse correlation technique that can be used to estimate the spatio-temporal receptive fields (STRFs) of sensory neurons from their responses to arbitrary stimuli such as auditory vocalizations or natural visual scenes. The general solution for STRF estimation requires normalization of the stimulus-response cross-correlation by the stimulus autocorrelation matrix. When the second-order stimulus statistics are stationary, normalization involves only the diagonal elements of the Fourier-transformed auto-correlation matrix (the power spectrum). In the non-stationary case normalization requires the entire auto-correlation matrix. We present modelling studies that demonstrate the feasibility and accuracy of this method as well as neurophysiological data comparing STRFs estimated using natural versus synthetic stimulus ensembles. For both auditory and visual neurons, STRFs obtained with these different stimuli are similar, but exhibit systematic differences that may be functionally significant. This method should be useful for determining what aspects of natural signals are represented by sensory neurons and may reveal novel response properties of these neurons.