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Background and aim: Chronic ankle instability (CAI) is a current disability that can affect on activity daily living of the patients. Many studies have indicated postural control deficits in these patients but the effect of a dual task on postural control has not been examined yet.

Materials and methods: Postural stability in CAI patients and healthy subjects was measured using the Force Plate. Eight positions concluded two different stances (double & single) with closed or opened eyes. All positions concurrently were done with a cognitive task. Anterior/posterior (Rfa) and medial/lateral (Rsw) mean sway quantified static postural stability.

Results: Mean sway significantly increased in patients in the anterior/posterior (single and double leg stance) and medial/lateral (single leg stance) directions (P<0.05). While performing a dual task anterior/posterior mean sway decreases within the patients group on the impaired leg stance (P<0.05). No difference is seen in the healthy subjects.

Conclusion: Postural control deficits were identified in participants with chronic ankle instability. In view of the fact that a cognitive task resulted in decreasing displacement of center of pressure in patients, this method may identify as an examination and a plan of treatment for affecting on ankle stabilizing factors.

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Background and aim: To investigate the effect of the light touch, vision and dual task interference on the surface electromyography (sEMG) activity of ankle muscles Participants: Thirty persons (12 male, 18 Female), right hand without any neuro-musculo-skeletal disorder and in healthy condition, participated in this study.
Methods and Materials: Participants stood in upright and semi tandem position. There was a high sensitivity sensor on the right side in direction of femur greater trochanter. They should press the sensor less than 50 gr. Also we examined the rate of activity in 3 muscles (Tibialis Anterior, Proneus Longuse, Soleuse) on both lower limbs by Biometrix sEMG device. 4 positions were experimented in semi tandem standing: No Touch, No Counting No Touch, Counting Light Touch, No Counting Light Touch, Counting. Each of the above positions was tested in 2 conditions: Eyes Open, Eyes Closed.
Results: Our findings detect that light touch contact especially during vision, resulted in reducing the rate of sEMG activity in the leg postural muscles. No touch and closed eyes, raise the rate of sEMG activity to maximum.
conclusion: On basis of findings, it seems that following skin receptors stimulation, some complicated mechanisms will be begun and in order to the orders of Central Nervous System (CNS), these muscles will make the hole body, stable. So it can reduce the entered pressure on leg postural muscles. Therefore we can see the lesser rate in sEMG activity of leg postural muscles.

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Background and Aim: in hemiplegic children Postural tone of the two sides of body is different. Once, asymmetric stance is a typical state in individuals' with unilateral pain and/or paresis and standing is with weight bearing on the stronger side. Obviously, an asymmetric stance with majority of weight bearing on the affected side can counter faces individual with the falling risk and causes instability. It seems coordinating of the two sides of body is the most vitally important therapeutic exercises in hemiplegic patients. Although stable stance is a simple postural task but it's controlled semi-automatically by cortical and spinal centers. It is established that stable standing, also demands cognition resources. So, postural control demands the interaction between musculoskeletal and nervous systems.
Material and method: In this clinical trial (before-after) 17 children 5-12 years old with spastic hemiplegia were participated. The subjects stayed in the center of force plate with the most stable standing position while using /not-using lateral wedge and in each state with/without doing cognition task. Short- memory test of digit span used as dual task condition. The mean range of fore-after and mediolateral sway and velocity and area as postural control independent variables and error measures in recalling of randomized digit chain as cognition task independent variables were registered.
Results: The wedge affected Rsw (P=0.015), Area (P=0.007) and Vm (P=0.005) significantly. Dual task also had significant effect on Rfa (P=0.014), Rsw (P=0.014), Area (P=0.002) and Vm (P=0.002). But the wedge declines its effect properly.
Conclusion: The results represent that a 5º lateral wedge applied to the unaffected limb, can improve factors of postural control even in Dual tasking thus The wedge can be used with a good effect on the posture of hemiplegic children.

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Background and Aim: Neck pain is one of the common diseases (66.7%), which contains different age's groups such as youn. Results of researches indicate prevalence of women neck pain is higher than men, so experiment in neck disease in female is more necessary. The aim of this study is to evaluate changes of postural stability in patient with muscular neck pain. 

Materials & Methods: Twenty patients and fifteen healthy subjects contribute in this study.  Postural sway in quiet standing was assessed in both limb stance (BLS), one limb stance (OLS) of dominant side, on a force platform with open eyes (rigid-open) and standing on a force platform with closed eyes (rigid-closed) and standing on the foam (10.5 cm-thick) with open eyes (foam-open) without shoes. All of above conditions were done with dual task. Mean changes of logarithmic displacement in medial-lateral and for- aft directions were calculated.

 Results: There are significant differences between two groups, especially following dual task, and difficult conditions of OLS and standing on the foam.

 Conclusion: Patients with neck pain have difficultly in postural control that need to attending in treatment and prevention of following damages.

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Background and Aim: Forces which applied to ankle joint for control of stability can cause damage to joint if it does not have suitable control. Chronic ankle instability (CAI) is a current disability that can affect on activity daily living of the patients. The aim of this study is to evaluate forces which contribute to control of posture in difficult conditions.

Material and Methods: Postural control was measured by force plate in two groups of CAI and healthy subjects. Eight positions were selected , including of double stances with closed or opened eyes, and single stances with opened eyes (right/ left) with and without a cognitive task. Force changes in two direction medial/lateral and anterior/posterior were evaluated with fractal time series analysis.

Results: Fractal dimension of force in two groups, following dual task in all of conditions reduced significantly (P<0.05). There was not significant different between two groups in double stance with or without dual task. Single stance in patients indicated significant increase of fractal dimension in affected ankle joint (P<0.05) but comparison of two side in healthy subjects did not have difference. Also there was significant increase of fractal in affected ankle joint of patients in comparison with similar side of healthy subjects (P<0.05).

Conclusion: Patients with (CAI) have a problem in regulation of force for control of posture. This difficulty increased and clearly indicated by dual task condition, which can cause susceptible qualifications for recurrent injuries. Fractal dimension is a suitable factor for analysis of control of posture in difficult situations.

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Background and Aim: Knee osteoarthritis is one of the most common musculoskeletal problems that can affect activity daily living of patients. Many studies have indicated postural control deficits in these patients but the effect of dual tasking on postural control has not been examined yet. The aim of this study is to investigat the effect of cognitive task on postural control in the female patients with knee osteoarthritis.
Materials and Methods: Postural stability in knee OA patients and healthy subjects (20 subjects in each group ) in four positions was measured using the Force plate. Positions included double leg stance with closed or opened eyes with and without cognitive task. Area of COP and mean velocity (Vm) were measured for as static postural stability.
Results: Area under the curve increased in the double leg stance position in the patients significantly (P<0.05). While mean velocity decreased by performing a dual task (P<0.05). The response to dual-tasking was not significant between the 2 groups(P>0.05).
Conclusion: Postural control deficits and increased of center of pressure’s sway were identified in participants with Knee osteoarthritis. Also performance of a cognitive task resulted in decrease of postural sway, but the dual- tasking did not change the postural performance of knee OA patients compared to healthy subjects.