focus of attention is widely used as a training method. This method helps to improve skill performance. The optimal focus of attention has always been a basic question for many researchers. The purpose of this study was to investigate the effect of different focus of attention instructions on muscular endurance of expert kung Fu athletes. In a semi-experimental design with repeated measurements 16 expert athlete of kung Fu were selected via available and purposeful sampling. They tried to perform the wall sit test under 4 different conditions internal focus (Attention to keeping the knee at 90 angle), the external near (focus on standing like a chair), external far (Attention to a computer screen displaying a chair) and control (without attention instructions). Within-group variance analysis results with repeated measurements showed that the control condition was meaningfully better than three other conditions (p<0.001). There was no difference between different distances in external focus (p=0.27). However, participants in both external conditions acted better than internal focus. Therefore, it can be said, the attention instructions interfere in optimal performance of expert athletes.