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Background and aim: The precise control of arm kinematics and kinetics as well as interaction of the arm with the external word, is an essential condition to perform skillful motor actions. Gravity has significant effect on spatial orientation, proprioception, displacement, start and stop of hand movements. The purpose of this research was to study the effect of movement direction variation in relation to gravity on generalized motor program recruitment in fast single joint elbow movement by use of surface electromyography.
Materials and methods: Fifteen volunteer students (mean age 24.8± 3.8 years) without sensory motor impairments participate in this study. Ninety percent of full range of motion at the elbow joint was used as goal degree. Subjects asked to do aimed elbow flexion as fast as possible in seven different direction in relation to gravity. While they were performing movements, surface electromyography was recorded from biceps and lateral head of triceps muscles. Relative timing, relative activity and sequence of contraction were derived from RMS. Data were analyzed by using repeated measure variance analysis.
Results: Muscle activation patterns were different in three positions from rest. There were significant difference between relative activity (p<0.001) and relative timing (p<0.003) in some positions. In fourth position, sequence of muscle contraction was different in seven subjects.
Conclusion: It seems that change in movement direction in relation to gravity is one of effective parameters in movement planning and execution and it can recruit different generalized motor program.

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 Background and Aim: There is an agreement on impression of environment on the development in different ways. The environment effect could be passive or active. The environment enrichment is a  passive method which is used to show the effect of  environment on the development during infancy.

The purpose of this study was to investigate the effect of early perceptual-motor enrichment on later fine motor development process of infants.

Materials and Methods: Fifteen 5 to 8-months-old healthy infants participated randomly in this study. According to their age, participants were divided homogenously in two groups: training (n=8, ages=6.5±2) and non-training (n=8, ages=6.5±2). Training group had 36 training sessions(3 times in a week) for an hour at a perceptual-motor enrichment environment (involve vary manipulation and locomotion tools). After 36 training sessions, at the first assessment stage, infant fine motor skills were evaluated by Peabody motor development scale. Three months later, all infants were kept in similar and normal condition. At the later assessment stage, after this three months, infant fine motor skills were evaluated by same scale. Data were analyzed by mixed ANOVA2 (group) × (stage). 

Results: Results indicated that in fine motor age equivalent, main effect of group(F_(1,10)=10.53 , P=.009 ) and main effect of assessment stages(F_(1,10)=96.33 , P=.001) was significant. Interaction between groups and assessment stages (F_(1,10)=2.58 , P=.13)was  not significant. Also,  in fine motor scaled score, main effect of group(F_(1,10)=6.65, P=.02) and main effect of assessment stages (F_(1,10)=32.93 , P=.001) was significant. Interaction between groups and assessment stages (F_(1,10)=.24, P=.63)was  not significant.

Conclusion: Generally, results show that training and experience have positive effect on later   fine motor skills development of infant.   

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Abstract

 Background and Aim: Regard with the importance of balance in daily activities especially in sport activities and understanding the important factor affecting it, the purpose of this study was to compare the role of vision system on dynamic postural stability of young women with men elite athletes.

Materials and Methods: Twenty six young women and men elite swimmer were chosen from the available society. They were divided in two groups according to body mass index. Each subject performed postural stability tests for 6 trials with open and close eyes (3 trials with open and 3 trial with close eyes) that each trial was taken for 30 seconds and with 10 seconds rest between each of them. Balance index in anterior- posterior and medial- lateral directions were calculated and independent t test was used to compare between groups.

Result: Results show that men swimmer are more depended to vision than women swimmer in maintaining retrieval postural stability (p= 0.001), while most impairment in maintaining postural stability in both groups occur in lack of vision status in anterior- posterior direction (p= 0.001).

 Conclusion: The findings of this study can be used to design training programs to prepare athletes.

Key words: balance, vision, athlete, control