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Recent evidence suggest that massive amount of practice of a skill results in the development of a specific memory representation that is distinguished by its enhanced performance capability relative to the other members of the same class that is uniqe and termed 'Especial Skill'. This study aimed to investigate the emergence of special skill and reevaluation the visual-context hypothesis using badminton players in three skill levels (expert, skilled, less-experienced). Subjects (10 players in each group, mean age=23.12 ±3.85 years) performered 100 backhand short serves at five distances (1.5, 2, 2.5, 3, 3.5 meters from net) in each of environmental conditions (normal and covered court). The regression analyze showed that accuracy in skilled group at 2 meters distance was significantly better than predicted by regression equation, supporting the especial Skill effect, but it wasn’t showed in two other groups. This specific advantage of practice at this point was not emerged at absence of visual cues that supported the visual-context hypothesis.

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Tools and methods that could lead to the recognition and motion analysis variables are helpful in understanding the movements and movement Sciences and It will be a vital part of movement and sport sciences laboratories. "Human motion analysis instrument based on joints angles in sagittal plane" was designed to provide information about the motion analysis that offers to researchers, educators and therapists. Once the instrument has been built according to the design of specialized electronic and mechanical engineers, tested until the fourth final design was made and it was registered on 21.05.1393 with number 83557. To check the validity, with using of motion analysis system with optoelectronic cameras and the instrument, 20 participants (10 males and 10 females) were asked to perform a throwing task. The root mean square error (RMSE) and Pearson correlation in the statistical 0.01 were used to assess the reliability and validity. The results indicate that the instrument is made applicable and appropriate validity and reliability so that the validity: 0.98 and reliability: 0.95 was reported.

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Measuring instrument of interpersonal and intrapersonal motor coordination has designed and built to provide information about the human movements’ coordination in reach of researchers, trainers and therapists. To evaluate the validation of this instrument with using of Vienna two hands coordination test and present research instrument were asked 28 participants to do the task of two hands, two feet and interpersonal movement coordination. Pearson correlation test showed that the present research instrument has high validation in motor coordination of two hands in total time mean factor of joystick (r =0/88), knob (r =0/96) and in error percentage mean factor of joystick (r =0/89) and knob (r =0/87). Also the results of Cronbach’s alpha showed that present research instrument has appropriate reliability in motor coordination of two hands in total time mean factor of joystick (r =0/89) and knob (r =0/97) and in error time percentage mean factor of joystick  (r =0/81) and knob (r =0/85). Also results indicated acceptable reliability in motor coordination of two feet in total time mean factor of pedals (r =0/90) and in error time percentage mean factor of pedals (r =0/83) and in interpersonal motor coordination in total time mean factor (r =0/91) and in error time percentage mean factor (r =0/80). Therefore using the present study instrument can be offered to sports science laboratories in all higher education institutions, federations and coaches, patients and rehabilitation centers, health and physiotherapy clinics.