The purpose of this study was to investigate the effect of task difficulty and the effectiveness of attentional instructions (baseline, internal and external) on balance task performance. Recent studies have shown that performer’s focus of attention plays an important role in the performance and learning motor skills, specifically when the task is novel and challenging for the performer. Forty eight students participated in this study and were divided randomly into two groups. Participants in each group performed three 15 balance tasks on a digital stabilimeter under each three conditions; without instructions, internal attentional focus, and external attentional focus. The results indicated that the performance of the difficult task group under external attentional focus was significantly better than other two conditions, while there wasn’t any significant difference in sway index among baseline, external instructions and internal focus conditions in each task group. It means that external focus will be more effective if the task is more challenging for performer. Therefore, the results indicate that the effectiveness of attentional focus as a learning variable depends on the difficulty of task.

Introduction: Most daily activities require cognitive processing in addition to balance demands they exert on the nervous system. The purpose of the present study was to compare the interference of selective attention and attention-shifting tasks in balance among the youth.Materials and Methods: In this cross-sectional study, thirty male students (mean age 22.47±2.27 years) were recruited from available research pools. Subjects were asked to perform single-foot standing task, which was measure by Biodex system, alone or coincidentally with either selective attention or attention shifting tasks. Selective attention and attention shifting were respectively evaluated via a “Stroop test” and the Neurological Attention Shifting test. ANOVA with repeated measures was used for the statistical analysis of the data.Results: Findings showed that both attentional tasks decreased balance performance on both frontal and sagittal plans and also overally (P<0.05). Similarly, attentional task scores were reduced by the balance task (P<0.05). The two attentional tasks interfere differently with balance task performance (P<0.05).Conclusion: Because same brain structures mediate attention shifting and selective attention processes and because these processes are interrelated, they may interfere with balance they combined with each other.

The aim of the present study was to introduce the methods to extract and to interpret cinematic data in order to explain movement pattern changes via joint coupling and freezing / freeing phenomena in a healthy right-dominant college male (age:26, height: 172 cm, weight: 80 kg) who practiced balance maintenance on a stabilometer. Data were gathered using a three - dimensional registration system which consisted of three cameras and a computer program (Sharif Motion Analyzer - SMA) in MATLAB software and measured the position of 19 passive markers located on subject's limbs and stabilometer. Before each trial, the system was calibrated by a metal frame of known dimensions to transform the two-dimensional camera detector values to real three-dimensional coordinates. Then, the following variables were calculated for the first, fifth and ninth trail from a 3(session) × 3(trail) course of practice: 1) stabilometer variability as a performance index; 2) absolute and relative variability of joint angles to evaluate possible freezing - freeing process; 3) cross-correlations between the angular time series in order to evaluate the presence of joint coupling. Finally, the interpretation method to extract variables was presented and some limits of such studies regarding the variability in degrees of freedom were provided.

The aim of this study was to investigate the effect of manipulating sensory and cognitive interference on the dynamic balance task. The research sample was consisted of 60 students of Urmia University of Physical Education with the 25-19 age range. Subjects were targeted in four groups: control, impaired vision, impaired somatosensory and visual removed and performed balance task in the balance system dynamic, once without cognitive task and once with the cognitive task. For analyze the data were used Analysis of variance with repeated measures, ANOVA and Tukey test. Results showed significant main effects test type and interaction with effect of group (P£0.01). In other words, the secondary cognitive task has significant effects on the dynamic balance. ANOVA test results showed a significant difference between groups in both types of test. Finally, the results showed that there is a paired difference between the groups, except of visual impairment with sensory impairment groups. As a result, the increased cognitive load can disturbed perform of dynamic balance task. Also the dynamic balance task is related to somatosensory and visual information and Impairment of the senses, causing a decrease in performance of optimal task.

Attention is one of the effective factors when learning and performing motor skills. Focus of attention is a method to increase the efficiency and learning. Previous studies have shown that focus of attention plays an important role in learning and performing motor skills. The purpose of the present study was to compare the effect of the instruction of far and near external focus of attention on dynamic balance task performance. In this study, sixty male undergraduate students of Ferdowsi University of Mashhad, who had taken the general physical education course in the second semester of 1388-89, were assigned randomly in three groups: far external attention group (attention to those signs far from the feet), near external attention group (attention to those signs near the feet) and control group (no attentional instruction). The stabilometer (Biodex) was used to collect the data. Each participant performed three 20-second trials in dynamic balance test. The obtained data were analyzed by descriptive statistics as well as inferential statistics such as one-way ANOVA and Duncan post hoc test. The results showed that far external attention group performed significantly better than control group while near external attention group did not reveal any significant difference compared to the control group.

The current research is to compare effects of self-control feedback and error estimation on acquisition and retention of balance task in children and adults. In this research a number of 96 students (48 children of 8 to 12 and 48 adults of 18 to 22) were collected and then randomly classified into 16 groups regarding age, sex, program of feedback and error estimation. The task was to keep balance for 30 seconds on estabiliometer. Acquisition stage was 4 sessions include 40 attempt were done in each session. Subjects received the feedback and estimate error related their groups. The subject’s performances were tested at the end 4th, 8th sessions. Retention test tested after 72 hours practice less period. The data were analyzed by variant (Repeated ANOV A). The results show that the main effect of feedback type was meaningful and the time of balance retention of self control group in acquisition exam was significantly better than coupled group, but the main effect of sex, self control and error estimation was not meaningful. In retention stage, the main effect of feedback type and sex was meaningful, and the time of balance in retention exam of men were significantly better than women, but the main effect of age level and error estimation was not meaningful (p<%5). Therefore according to results of this research, we conclude that the self-control exercise method, especially self-control feedback is effective in acquisition and retention skills in children and adults. The error estimation in self control group also has a better application in acquisition process.

Objectives: Studies have shown that doing dual tasks during walking could radically change the pattern of walking even in healthy older people. The study of spatial-temporal parameters and their changes in walking with dual tasks, symmetry in right and left legs functions as well as changes in these parameters have received scant attention from researchers. Therefore, the purpose of this study was to evaluate the changes in spatial temporal parameters of walking due to their simultaneous execution with cognitive dual-task in older people with impaired balance.Methods & Materials: Thirty older adults with weak balance voluntarily participated in this study. The study subjects were selected through Berg and Mini-Mental State Examination (MMSE) tests. The subjects who got scores lower than 52 in the Berg test were allowed to participate in the study. On the other hand, those who got scores lower than 23 in the MMSE test were excluded from the study. After subjects’ familiarity with the measurements and taking their informed consents, they walked 12 meters under 2 conditions; normal walking and walking with a cognitive dual-task. Spatial-temporal kinematic parameters were recorded by Vicon cameras. Then, by using the Polygon software, the variables of cadence, walking speed, step length, stride length, duration of step and stride, duration of stance and swing, time of single leg support and double leg support, separation of other leg, touching of other leg to the ground, and time of separation of fingers were calculated in terms of percentages of walking cycle. The obtained data were analyzed using repeated measures ANOVA at a significant level of P<0.05.Results: The results showed that among the examined parameters, the variables of cadence and walking speed during walking with dual-task were reduced significantly compared to normal walking. The duration of the step, stride, time of double support, time of single leg support, the time of standing and swing in walking along with dual-task compared to normal walking showed a significant reduction (P<0.05). Asymmetry index in walking with dual-task compared to normal walking showed a significant increase in parameters of cadence, duration of step and stride; however, the changes in other parameters were not significant. The findings showed that the changes in stepping parameters from one step to the next one in walking with dual-task compared to normal walking had no significant changes. In other words, the older people with impaired balance had similar steps. Moreover, despite a significant decrease in speed and stance and swing time, the timing of the 2 phases of stance and swing with and without dual-task did not show any significant differences.Conclusion: The results showed that the duration of double reliance and stance increase when walking with dual task than when normal walking. Therefore, in the elderly with poor balance, doing dual-task with walking could increase the risk of fall. With regard to increase in asymmetry in walking with dual-task, it seems that mutual harmony and symmetry is very sensitive to concurrent cognitive task. This asymmetry in the function of legs is considered a risk factor in falling. Thus, based on the results, walking of the elderly with poor balance needs better cognitive performance. Doing concurrent cognitive tasks could intervene with attention sources and consequently change the walking pattern. Therefore, we recommend that the older people with weak balance and prone to falling should refrain from cognitive dual-task during walking and focus on walking itself.

Introduction: Balance assessment plays a major role in treatment and rehabilitation of patients. Recently scientists have designed a new device with a dynamic multi-axial tilting platform to aid in joint rehabilitation and enhance proprioceptive mechanisms and postural assessment, called Biodex balance system (BBS). Repetition of exposure to the BBS causes learning or familiarization. Therefore, it can’t be sure that the changes seen in the stability index, are due to the effect of the learning or intervention. The purpose of this study was to evaluate the learning effects of test-retest postural task and to set the learning curve and test-retest reliability of dynamic standing balance using BSS.Materials and Methods: Ten healthy non-athletic persons participated in this study. The volunteers were asked to stand on BBS with two levels of difficulty on their dominant leg with open eyes. Two trials of 10 repetitions were applied at difficulty level of 4 and 8 with 30 minutes rest between each test and 30 minutes rest between two trials. Total stability index (TSI), anteroposterior (APSI) and mediolateral (MLSI) were registered.Results: The effect of repetition of hard postural task on biodex was significantly different in trial 6 from 1-5 (P<0.05). The effect of repetition of easy postural task on biodex was significantly different in trial of 5 from 1-4 (P<0.05). After learning, we found no significant difference in mean stability index of test condition of each trials in reliability assessment so the intra-class correlation coefficients ranged from 0.83 to 0.92. Tests at lower stability level produced the higher ICCs (0.90- 0.92). There was a very strong correlation between total stability index and AP stability index using Pearson correlation coefficient (P<0.01, r=88%).Conclusion: The results showed that repeating a task on the BBS for five times or more have learning effects. So, while evaluating postural stability in a simple task which has more than five repetitions, learning effect should be take in to account and in difficult postural task it is sex repetitions that can have learning effects.

Purpose: The purpose of present study was to determine the effect of different levels of balance task difficulty and visual feedback on EMG activity of selected muscles in elderly women. Methods: Fourteen healthy elderly women (mean age 57/65 yr) were voluntarily selected. The task consisted of performing balance task on Biodex Balance System. Participants were asked to stand still on a stability platform under two conditions (with and without visual feedback) in three levels of difficulty (6, 8 &10). Megawin EMG system was used for recording electromyography of rectus femoris, gastrocnemius, preroneus longus and biceps femoris muscles and RMS of EMG signals was obtained. Duration of each test was 20 seconds and rest times were 20 seconds. Results: Results showed that with increasing task difficulty, preroneus longus (p= 0/01), biceps femoris (p= 0/028), rectus femoris (p< 0/001) and gastrocnemius (p= 0/01) EMG activity increased significantly. In addition, there was a significant increase in preroneus longus (p= 0/01), biceps femoris (p< 0/001) and rectus femoris (p< 0/001) EMG activity in visual feedback condition compared with without feedback condition. Conclusion: As task difficulty increased and with visual feedback, the elderly did not choose between two postural strategies but tend to combine movements in continuous behavior and they use the body stiffness strategy to improve balance.