The aim of our study is to compare the effects of the Copenhagen adduction exercise, performed at different loading intensities, on hip muscle strength development, performance, flexibility, and delayed onset muscle soreness. The study will include active taekwondo athletes between the ages of 12-18. Athletes will be randomly divided into two groups: a low-intensity Copenhagen Adduction exercise group and a high-intensity Copenhagen Adduction exercise group. Athletes in both the low-intensity and high-intensity exercise groups will perform the exercise for 8 weeks in addition to their regular training program. At the beginning of the study and at the 4th, 8th, and 16th weeks, assessments will be conducted for hip abductor and adductor eccentric and isometric muscle strength, flexibility of the hip adductors, level of delayed muscle soreness, single-leg jump test, and timed lateral hop tests. The outcome of our study will determine how much improvement is achieved in hip muscle strength and lower extremity physical fitness parameters during and after the application of the Copenhagen adduction exercise at different loading intensities.