The aim of this study was to compare the effects of Imagery ability (clear mental, vague mental practice) on muscles electrical activity on hand grip task acquisition, retention and transfer. 45 girls (18-28 years old) of Islamic Azad University, were selected randomly. Force production in two, clear mental and vague mental modes were registered using Encoder Electromyography System. According to the instructions, experimental groups practiced 18 hand grip practices for each session, three sessions per week, 4 weeks long, in 2 blocks. At the end of the 4th week, acquisition test, and immediately transfer test at different values (12 kg) were administered and electromyograms were obtained. Three days after the last practice, retention test,was administered and electromyograms of contractions in the respective ranges were registered. Kolmogorov–Smirnov Test, Independent Groups T-Test, One-Way Analysis of Variance Test and Tukey’s Test were used for data analysis and hypothesis testing. Results showed a significant difference between clear mental group and control group, between clear mental group and vague mental group, in hand grip acquisition at 12 kg force. None of clear mental practice, vague mental practice groups caused significant changes in electromyography at retention stage, at 12 kg force. Thus, clear mental practice had significant effects on electromyographic changes in transfer stage at 12 kg.
