Abstract: This study aimed to examine the effects of different attentional focus instructions on muscles activity and performance during squat exercise. Participants were randomly divided into three groups (i.e., internal focus (IF), external focus (EF) and control). Electromyography (EMG) was used to measure muscle activity of the lower limbs (i.e., vastus lateralis, bicep femoris, gluteus maximus) while Movement Competency Screen measured the performance of the squat. There was a significant interaction between the groups, muscles and test. No between group differences in EMG reading of the three muscles during pre test. However, the EF group showed significantly lower EMG reading than IF and control group in the post as well as retention tests. There was also a significant interaction between group and test in performing the squat. Both EF and IF groups were significantly better in performing correct squat repetitions than the control group during post and retention tests. In conclusion, the combination of muscle activity and performance showed that EF of attention’s instructions were more efficient because it reduced muscle contraction and improved performance compared to IF instruction which only improved performance but increased muscle contraction.