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.

Background and Aim: Perceptual motor abilities are based on motor functions and conceptual growth. Therefore, regarding the weak perceptual motor abilities in mental retarded children, it will be an effective step in eliminating their learning problems and improving their functional activities at school, at home and in the society. The purpose of this study is to investigate the effect of instruction of balance exercises along with gross movement exercises on the balance function and gross movement in mental retarded children.

Materials and Methods: Using a simple non-probability sampling method, based on a pilot sample and the sample size formula were considered 10 children in the treatment group and 10 children in the control group. Inclusion criteria include educable children with mental retardation without significant skeletal, neurological and mental illness and the age group is between 4.5 to 14.5 years. Exclusion criteria include uncooperative child and absence of more than one session. Treatment group for 10 weeks, 3 sessions per week for 30-minute exercises; balance training and gross motor was taught. No intervention was done on control group. Then all subjects retested. The effectiveness of the treatment on balance and gross motor function were performed by statistical analysis.

Results: Before treatment, balance and gross motor scores were not significant (P&ge;0.05) between the intervention and control groups. In the interventional group, gross motor scores were significant (P&le;0.05) but balance scores were not significant (P&ge;0.05). Balance and gross motor scores between pre-and post-intervention in control group were not significant (P&ge; 0.05).

Conclusion: Lack of experience in the motor skills resulted poor motor skills in mental retarded children. Therefore, according to the findings of this study, we can provide requirements for gaining motor experiences with planning, targeted training and utilization of effective rehabilitation and occupational therapy.         

Keywords: Balance exercises, Gross exercises, Mental retardation