Purpose The purpose of this study is to investigate the effects of Shaker exercise (SE) and modified Shaker exercise (MSE) on the activity of the suprahyoid (SH), Sternocleidomastoid (SCM), anterior scalene (AS), splenius capitis muscles (SC). In addition, we want to investigate whether there is a difference in muscle activity and fatigue during SE and MSE according to forward head posture (FHP). Methods Thirtynine healthy adults participated in this study. All subjects performed SE and MSE isometric exercise, and the exercise sequence was counterbalanced. SE and MSE measured the mean, maximum, and fatigue levels of SH, SCM, AS, and SC muscles using surface electromyography. All exercises were repeated 5 times and were performed isometrically for 20 seconds, with an interval of 30 seconds between exercises. A 20minute break was provided between the two exercises. For reference voluntary contraction, 90˚ abduction was performed 3 times based on the middle deltoid muscle. The craniovertebral angle was measured to determine the FHP. Results SH and AS, SC muscles activation was significantly higher in MSE than in SE (p<.05). There was no significant difference in SCM muscle activity and fatigue between the two exercises. In SE, the group with FHP less than 50 degrees showed significantly lower activity in SH and SC muscles than the group with 50 degrees or more. Conclusion These findings suggest that MSE can be used as a more effective method for enhancing SH muscles than conventional SE.