Objective Quantify the lower limb muscle synergy characteristics of athletes during the abdominal take-off phase before and after fatigue, and reveal the impact of exercise fatigue on the lower limb muscle synergy characteristics of athletes during the abdominal take-off phase. Methods The surface electromyographic data of the lower limbs during the abdominal take-off phase of 10 second-level male athletes in track and field special classes before and after exercise fatigue intervention were compared. The muscle synergy structure before and after exercise fatigue was analyzed. The paired sample T test method was used to compare the differences in synergy parameters before and after. Results Two synergistic elements were extracted before and after fatigue, and there was alternate activation of muscle synergy structures. After fatigue, the activation degree of Synergy element 2 decreased significantly,dropped from 53.21±7.90 to 53.21±7.90.but there was no significant change in Synergy element 1. After fatigue, the contribution of the rectus femoris muscle of Synergy element 1 significantly increased,increased from 0.37±0.04 to 0.44±0.07, and the contribution of the semitendinosus muscle decreased significantly,0.13±0.05 dropped to 0.08±0.05. Conclusions During abdominal take-off, as fatigue increases, the activation degree of the synergistic elements of each lower limb muscle decreases, and the contribution of the rectus femoris muscle in Synergy element to absorb the ground reaction force increases, suggesting that the rectus femoris muscle is at risk of strain, and prevention of the rectus femoris muscle should be strengthened. muscle damage.