Background and Aim: Forces imposed on body members even on light working condition, may gradually result in damages caused by working. Persons engaged at goods sales centers including cashiers, may be to catch exhaustion and neuromuscular damage due to repetition of their wrist, elbow and shoulder joints movement. The aim of this research is to assess the relation between the work factors and personal characteristic in possibility of the above symptoms.
Materials and methods: The questioners form propounded at Stanford university question were asked and coded based on the target group, and having been reviewed and surveyed were later used in this research. This questioner included parts such as recording the personal characteristics, history of illnesses, clinical diagnosis and evaluation of the work environment and the hand tools. Selected individuals were randomly employed at goods sales centers from five geographical districts of Tehran.
Results: The most complaint of employees was pain and dysfunction in upper limbs, neck and shoulder. Half of subjects had carpal tunnel syndrome.
ength of work time and employment duration at sales centers increase probability of neck and shoulder pain.
Conclusion: The profession of cashiering at sales centers is one of the most stress causing jobs on the peripheral joints of upper limb, so that the lengths of working in this position and the amount of activity have a positive effect on the increase of neuromuscular disorder. Apply of correct pattern of using the tools and the equipment in this work environment could substantially control the negative effects of this type of job. The most of complains expressed by individuals taking part in this research have been related to sign and symptoms of involvement of median nerve in the wrist and referral pain in the neck, shoulder and arm.

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.