ABSTRACT The Gluteus Maximus muscle is crucial for various functional movements, serving as both a trunk and hip extensor. If this muscle becomes weak, it can lead to problems with pelvic and hip joint function, as well as contribute to lower back pain. The prone hip extension (PHE) exercise is widely utilized in clinical settings due to its effectiveness in activating the Gluteus Maximus muscle. To compare the changing of hip and shoulder angles on electromyographic activity of the Gluteus maximus muscle and the contralateral lower fibers of the Trapezius muscle and to correlate between the activity of the Gluteus maximus muscle and the contralateral lower fibers of the Trapezius muscle. Thirty-one healthy adults according to sample size calculation, after achieving the inclusion and exclusion criteria, their age ranged from 18 and 25 BMI were 20.8-24.4 an informed consent was filled out by each participant before the beginning of the study. Thirty-one subjects were allocated to perform prone hip extension (shoulder abduction angles of 125°, hip flexion angle of 20° and combined shoulder abduction of 125° and hip flexion 20°). The study's results indicated a statistically significant difference in Gluteus Maximus EMG activity among the three positions (PHE with a 125° shoulder abduction angle, PHE with a 20 hip flexion angle, and PHE with a 125° shoulder abduction angle combined with a 20 hip flexion angle), favoring position 3. Additionally, there was a statistically significant difference in Lower Trapezius EMG activity among the three positions, also favoring position 3. Prone hip extension with a 125° shoulder abduction angle combined with a 20 hip flexion angle is recommended as the position for maximizing activation of both the Gluteus Maximus and Lower Trapezius muscles.