This study aimed to assess the effects of progressive lumbar stability exercises and lumbar stability exercises on changes in the transversus abdominis muscle thickness and lower extremity muscle fatigue index in soccer players. Ten subjects were assigned to undergo training in each of the 2 groups, namely, the progressive lumbar stability exercise group and lumbar stability exercise group. Each intervention session lasted for 30 min, and 4 sessions were conducted in a week for 6 weeks for soccer players of S. University in Jeonnam, Korea. Changes in the transversus abdominis muscle thickness and lower extremity muscle fatigue index were measured using ultrasound and surface electromyogram. The results of the ultrasound measurement for the transversus abdominis muscle thickness indicated that progressive lumbar stability exercises were more effective than lumbar stability exercises. The results of the lower extremity muscle fatigue index measurements using surface electromyogram indicated that the fatigue index decreased in the progressive lumbar stability exercise group. Progressive lumbar stability exercise is believed to have put more workload during the shaking of the limbs, leading to increased stability and increased efficiency of the lower extremity muscle, thereby decreasing the fatigue index. Therefore, progressive lumbar stability exercises can be an effective measure for preventing injuries and improving the game performance of sports players by increasing the transversus abdominis muscle thickness and decreasing the lower extremity muscle fatigue index.