Introduction: Fatigue accumulation in the final 100m of a 400-m sprint impairs neuromuscular coordination and biomechanics, often resulting in performance decline. This study investigated how fatigue affects lower-limb coordination, joint mechanics, and recovery patterns in competitive sprinters. Methods: A randomized controlled trial was conducted with 30 trained male Chinese 400-m sprinters (age: 29.8 +- 2.7 years), allocated into control (n 5 15) and experimental (n 5 15) groups. The experimental group completed five 80-m maximal sprints with decreasing rest intervals before running a 400-m sprint; the control group performed only the 400-m sprint. Kinematic and EMG data were recorded during the final 100 m. Recovery measures-Rating of Perceived Exertion (RPE), Jump Height, Peak Force, and Peak Power -were assessed at 30 min, 1 h, 3 h, and 36 h post-sprint. Data were analysed using two-way ANOVA and paired t-tests. Results: Fatigue significantly increased stride variability in the experimental group from 0.022 +- 0.010m (Session I) to 0.035 +- 0.012m (Session II, P < 0.0001), while hip flexion decreased from 33.1 +- 4.58 to 26.7 +- 3.98 (P 5 0.0012), and CRP rose from 15.6 +- 2.98 to 24.1 +- 4.28 (P 5 0.002). EMG activation declined in key muscles, including Rectus Femoris (0.28 +- 0.05 to 0.23 +- 0.05, P 5 0.0035) and Soleus (0.21 +- 0.05 to 0.18 +- 0.04, P 5 0.0003). RPE increased from 10.9 +- 2.05 to 19.5 +- 1.20 at 30 min post-sprint (P < 0.0001), with Jump Height decreasing from 49.5 +- 5.02 cm to 34.8 +- 5.10 cm (P < 0.0001), Peak Force from 17.8 +- 1.28 to 15.1 +- 1.42 N kg
1 (P 5 0.0012), and Peak Power from 65.7 +- 6.03 to 50.4 +- 4.95W kg1 (P < 0.0001). Conclusion: Fatigue in the final sprint phase significantly impairs joint coordination, muscle activation, and power output. These findings highlight the need for targeted fatigueresistance training and individualized recovery protocols. A limitation is the all-male sample, which may affect generalizability.  Kulcsszavak: fatigue, biomechanics, muscle strength, electromyography, running, recovery of function