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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: Knee osteoarthritis is one of the most common musculoskeletal problems, can affect on patient's daily activity and produce dependency in their daily activity and functional disability The aim of present study is to compare static balance in patients with knee osteoarthritis and healthy subjects using force plate. 

Materials & Methods: Postural stability in knee OA patients and healthy subjects (each group 20 subjects) were measured by force plate. Two positions were selected double stance with closed or opened eyes. Range of fore/aft (Rfa) and Range of side ways (Rsw), were measured as static postural stability.

Results: Rsw increased significantly in the double stance position in patients group (P<0.05). Also in both groups, Rsw and Rfa in the double stance with closed eyes were more than of open eyes position (P<0.05).

Conclusion: Postural control deficits and increase of center of pressure's sway were identified in participants with knee osteoarthritis. Therefore, one of the most important goals of rehabilitation is to improve balance control in knee OA patients.

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Background and aim: Flexible flat foot is a common deformity in lower extremity, the foot arch collapses and the ground reaction forces does not apply properly to the foot. Backward walking is a common rehabilitive technique and is utilized to improve strength and balance. The purpose of this present study is to compare the salient points vertical ground reaction force measurements in flat foot patients while walking forward and backward with those of healthy subjects using a force plate system.
Materials and methods: 10 flexible falt foot female subjects  and 10 healthy female  subjects were  recruited to participate in this study. Each Subject walked 5 times forward and 5 times backward and the vertical ground reaction force was measured by a force platform.
Results: The results of this present study suggest a significant difference in kinetic pattern of forward walking compared to backward walking in both healthy and flexible flat foot participants. The force related to first peak of vertical ground reaction force was significantly less in forward walking compared to backward walking (p=0.000). Whereas the force related to trough and second peak of vertical ground reaction force were significantly high in forward walking compared to backward walking (p=0.000).
Conclusion: The results of this study show that backward walking changes the ground reaction force compared to forward walking and the main characteristic of this difference is due to decrease of forces applied to the heel of foot which may be important in flat foot patients.

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Background: Flexible flat foot is a congenital common deformity in lower extremity associated with ligamentus laxity. This deformity may cause hammer toe, heel spur, inflammation of achille tendon, early muscle fatigue during sport, foot imbalance and pain in leg, knee and hip. The use of insole with medial arch support considered as one of the common treatments for patients. The purpose of this study was to determine the effect of a composite insole, Ethyl Vinyl Acetate (EVA) with Poron layer on ground reaction force on subjects with flexible flat foot in comparison with common EVA insole.

Materials and Methods: Fifty two subjects (14 Male and 38 female) between 18-40 years of age with flexible flat foot participated in this study. Twenty six subjects received Poron insole (EVA with Poron layer) and 26 subjects received common EVA insole. After assessment each subject asked to walk with normal speed across two force plate in two conditions, walking with insole and shoe and walking without insole. Then each subject asked to use insole for forty hours during two weeks. Vertical ground reaction force in the first session and after two weeks was assessed.

Results: Impact force and first peak of vertical ground reaction force (F₁) with Poron insole in comparison with shoe significantly increased in second session (P<0.05). The second peak (F₃) with common insole in comparison with shoe significantly increased in second session (P<0.05). Significant reduction was noted in first peak (F1) with common insole in second session in comparison with first session (P<0.05). There was no observable significant difference in two groups before and after intervention.

Conclusion: The results of this preliminary study show that both insoles change vertical ground reaction force in comparison with shoe alone. But using a composite Poron Layer on EVA insole has not demonstrated a significant difference with common arch support insoles. Therefore application of Poron Silicon layer on EVA insole by itself can not show a significant reduction of ground reaction force.

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Background and aim: One of the common problems in elderly people is falling. The effort to identify environmental risk factors at home and their modifications may control falls and injury in the elderly. Home FAST as a valid and reliable screening tool is used to identify elderly at risk of falling at home and in society.
Materials and methods : International quality of life assessment (IQOLA) was used for validity and reliability of Home fast. After forward and backward translation , the questionnaire was evaluated for content validity by 5 occupational therapists. Sixty participants aged over 65 were randomly selected through five geographical regions of Tehran. Inter-rater and test-retest with one week interval were conducted by two occupational therapists.
Results: Agreement among experts about the validity of screening tool of Home FAST (χ²= 25.008) were more than 96%.The correlations of test-retest with relative and absolute coefficients were high (ICC = 0.72 and SEM = 0.89). Also, the correlation coefficients between the raters with absolute and relative (ICC = 0.88 and SEM = 0.54) were significant, indicating the high reliability of this test.
Conclusion: This study shows the reliability and validity of the test are high. Since, test items are conformable to fall prevention goals, these results can be expected. The tool can be used by professionals.

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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.

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Abstract

Background and Aim: Proprioceptive problems, visuospatial deficits and muscle weakness are the main causes of weight bearing asymmetry and postural control impairment in chronic hemiparesis patients. The aim of this study was to investigate the correlation between center of pressure parameters in quiet standing with eyes open and closed and functional balance tests and symmetry index in these patients.

Materials and Methods: In this correlation study, 16 stroke patients (mean age: 52.937±10.109 years), were selected by simple non-probability sapling. Force plate, Functional Reach and Timed Up and Go tests and scales were used in order to investigate postural sway parameters in quiet standing, functional balance and symmetry index, respectively.

Results: Moderate to high significant correlation was obtained between Timed Up and Go test and symmetry index and most of the postural sway parameters in eyes closed condition, while Functional Reach test had only moderate significant correlation with standard deviation of velocity (anterior-posterior) and phase plane total. Also symmetry index showed moderate correlation with most of the postural sway parameters.

Conclusion: Current study demonstrates the role of vision and task in correlation between center of pressure parameters, balance tests and symmetry index.

Key words: Correlation, Symmetric weight bearing, Postural sway, Functional Reach, Timed Up and Go, Force plate, Quiet standing

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Background and Aim: Muscle fascicle length and pennation angle can be non-invasively studied by applying methods like ultrasonography. The aim of this study was to introduce fascicle length and fascicle angle for the estimation of the strength of skeletal muscle by using ultrasonography.

  

Materials and Methods: The data of this study have been driven from pubmed and authoritative references available on the internet and in libraries. In all fifteen full text articles and 30 abstracts have been collected and reviewed. Keywords such as: muscle, fascicle, pennation angle, force and ultrasonography were searched to fulfill the purpose of this study.

  

Results : Detailed information about the angles of pennation and fascicles length are important to predict muscle force. It has been suggested that changes in muscle pennation angles are positively correlated to the length of fascicle in a muscle contraction. While muscle thickness may in some case be remained constant in this relation.

  

Conclusion: Real-time ultrasonography is a noninvasive procedure to monitor the architecture of the living muscle at rest and during static and dynamic sets. It is a valuable measurement tool to estimate muscle force by measuring the muscle architecture parameters such as angle of pennation and fascicle length.

 

Keywords : Muscle, Fascicle, Pennation angle, Force, Ultrasonography

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Background and Aim: An immaculate review of the literature reveals some changes on the vertical ground reaction force (VGRF) in ACL deficient knee subjects. However, the details are not clear yet. The current study aimed to study these changes in the ACL-deficient and apparently healthy knees of the coper and non-coper ACL-deficient knee subjects in comparison with the normal knees.

Materials and Methods: Sixteen unilateral ACL-torn subjects included 8 copers and 8 non-copers were recruited in this quasi-experimental study and were compared with 16 normal knee subjects (8 subjects matched to each coper and non-coper groups). All subjects walked barefoot and with their preferred speed in a 6-meter walkway and placed their wanted foot on the platform of a Zebris pedobarograph tool. The patients were asked to place their injured and healthy feet separately on the platform. The control group placed their foot matched to the ACL-deficient legs on the platform. The testes were repeated so much to have five acceptable trials. The outcome measures included the peak F1Z, F2Z, F3Z of the vertical ground reaction force values and the times to reach these peak values as well as total stance time of the tested feet.

Results: The results showed only a significant lower F₁Z value in the non-coper ACL-deficient knee subjects (p=0.008). No significant changes were shown in the F₂Z, F₃Z or the times reach to F₁Z, F₂Z and F₃Z values (p>0.05). The stance time of the coper ACL-deficient knee subjects increased significantly in the non-coper ACL-deficeint knee subjects when compared to the coper and healthy knees (p=0.005).

Conclusion: The reduced F1Z of the vertical ground reaction force at initial contact as well as increased total stance time seen only in non-coper ACL-deficient knee subjects reveals inadequate compensatory mechanism in these patients as a counter force stress at initial contact and weight bearing. However, the coper ACL-deficient knee subjects compensated these forces with good strategies and walked very similar to the control group.

Keywords: Vercial ground reaction force (VGRF), Time to peak vertical ground reaction force components, Coper & non-coper ACL-deficient knee subjects, Pedobarography.

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Background and Aim: Postural control is the ability of maintaining of the body posture in space. Peripheral and central factors have important role in muscle fatigue. Repetitive muscle contraction leads to muscle fatigue. If strength is educed up to 30% of maximum contraction can be disturbed stance control of subjects. The objective of the present study was to compare the effect of lumbar muscle fatigue on postural control in athlete and non-athlete subjects.

  

Materials and Methods: Fifteen men as athlete subjects and other fifteen matched men as non- athlete subjects participated in this study. Trunk extensor muscle fatigue was produced by dynamometer. Stance postural sways were evaluated by force platform device in bipedal stance with open eye.

  

Results: In pre-fatigue state there is no significant difference between two groups. Fatigue had significantly effect on postural sways in both group after Lumbar muscle fatigue specially in non-athlete group (P ≥ 0.05) .

  

Conclusion: The postural control of athletes after muscle fatigue was better than non athlete subjects probably due to better proprioception in athlete subjects.

  

Keywords: Muscle fatigue, Postural control, Force plattform.

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Background and Aim: The calculated parameters of the center of pressure (COP) are suitable indicators for evaluating balance in patients after rehabilitation. Therefore, determining the reliability level of each parameter is a matter of great importance. This study tried to determine the reliability of some parameters of the COP sway in patients with myofascial neck pain in different postural situations.

  

Materials and Methods: The present study is a test-retest reliability design. Twenty patients with myofascial neck pain performed a single and a double leg test with open and closed eyes on a force plate and with open eyes on foam in three sessions with a 30 minute intervals for 30 seconds. Antero-posterior and medio-lateral sway range, mean velocity and mean area of sway were calculated.

  

Results: The mean velocity showed high reliability (0.98) in all situations, but the other parameters were variable in different situations.

  

Conclusions: The results showed that some COP parameters are highly reliable in assessment of patients with myofascial neck pain.

  

Keywords: Reliability, Myofascial neck pain, Center of pressure, Force plate

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Background and Aim: Anterior cruciate ligament (ACL) injury is common in sports competition and training. Following ACL rupture, neuromuscular system performance is disrupted. Perturbation training can improve the function of patients with ACL reconstruction. The aim of the present study was to assess the effects of perturbation training on ground reaction force and functional status of these patients .

  

Materials and Methods: Twenty patients with ACL reconstruction were randomly assigned into intervention (mean age: 24/2 ±3/4 years) and control (mean age: 27/1 ± 2/5 years) groups. The intervention group performed ten sessions perturbation training with rocker board, wobble board and Bosu. Peak vertical ground reaction force (GRF) and time to peak vertical GRF were recorded by KISTLER force plate during single leg landing from a 30cm height step. In addition, cross hop test also was evaluated as a functional test.

  

Results: Before perturbation training, both GRF and time to peak vertical GRF in reconstructed knee had not significant difference between two groups (P>0/05). In addition, functional test score had not significant difference between the groups (P=0/62). Following perturbation training, peak vertical GRF in reconstructed knee was greater than that in control groups (P<0/003).Although time to peak vertical GRF in reconstructed knee increased, there was not statistically significant difference between two groups (P=0/50). Furthermore, functional test score was statistically greater in intervention group (P=0/03).

  

Conclusion: This s tudy showed that perturbation training can improve functional status in patients with ACL reconstruction. In addition, force plate findings indicated that the patients tolerated more forces at longer time in single leg landing.

  

Key words: Perturbation training, Ground reaction force, ACL reconstruction, Function

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Background and Aim : Chronic non-specific low back pain is one of the important health problem in military and different factors have been reported in its emergence. The aim of this study is to determine the association between low back pain and education level, Body Mass Index (BMI), exercise, smoking status ,work status and bad postures in military men.

  

Materials and Methods : In this non-experimental case-control study, 92 subjects (mean age= 29.16 year, SD= 8.55 year) with chronic non-specific low back pain and 93 subjects (mean age= 26.80 year, SD=9.22 year) without low back pain were selected by simple non-probability method from military centers in Tehran. Evaluation tools of this study included a self-administrated questionnaire, weighting scale and metal tape measure.

  

Results : According to the results of bivariate logistic regression, risk factors of exercise (P= 0.003), smoking status (P= 0.042), grade of BMI (P= 0.034), bad posture grades including heavy objects lifting movements (P= 0.007), bending movements (P= 0.003), rotating movements from the lumbar (P= 0.011), carrying bulky objects (P= 0.034), carrying heavy objects (P= 0.05) and working in squatting position (P= 0.005) had a significant association with low back pain. Job status (P= 0.999), education level (P= 0.056) and bad postures grades movements like wringing clothes (P= 0.958) had not a significant association with low back pain.

  

Conclusion : Doing regular exercise and having normal BMI decrease the risk of suffering from low back pain in the military while smoking and doing injurious physical activities during work (lifting heavy objects, bending movements and rotating from the lumbar, carrying bulky and heavy objects, and working in squatting position for a long time) increase the risk of suffering from low back pain.

  

Key Words : Chronic non-specific low back pain, Military forces, Biomechanical risk factors, Exercise

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Background and Aim: Standing stability is resulted by normal functioning of various neuro-muscular and musculo-skeletal systems. Patients with below knee amputation cannot use ankle strategy due to limb loss and they have to rely on other mechanisms to improve their standing stability. The effect of prosthesis foot on standing stability of patients with below knee amputation is not well understood. Therefore, the aim of this study was to evaluate the stability of below knee amputees and determine the influence of prosthesis foot on stability

Materials and Methods:  Fourty subjects participated in this study. Participants were divided into three groups including:  (a) normal individuals, (b) amputees using SACH foot and (c) amputees using single axis foot. The stability of subjects was evaluated by use of a Kistler force plate. The subjects were asked to stand on the force plate for one minute and look forward with their hand at their sides. The stability was evaluated by use of some parameters such as excursion of Center of Pressure (COP) and path length and velocity of COP in mediolateral and anteroposterior directions. The difference between the stability of the subjects was determined using One-way ANOVA and Post Hoc test.

Results: There was a significant difference between stability of the three groups during standing with regard to path length and velocity of COP in mediolateral and anteroposterior directions (P < 0.05). No significant difference was reported with regard to all of the measured parameters when comparing normal individuals and amputees with single axis foot (P >0.05).

Conclusion: Below-knee amputees standing stability who are using single axis foot have the same standing stability compared to normal subjects; moreover, stability of amputees who are using SACH foot was surprisingly better than normal subjects in some of the parameters including path length and velocity of COP in mediolateral and anteroposterior directions.

Keywords: Standing stability, Below knee amputation, SACH foot, Single axis foot, Force plate