Fatigue-induced changes in muscle coordination and their impact on performance decline during the 400-meter sprint

Fatigue accumulation in the final 100 m 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.

A randomized controlled trial was conducted with 30 trained male Chinese 400-m sprinters (age: 29.8 ± 2.7 years), allocated into control (n = 15) and experimental (n = 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.

Fatigue significantly increased stride variability in the experimental group from 0.022 ± 0.010 m (Session I) to 0.035 ± 0.012 m (Session II, P < 0.0001), while hip flexion decreased from 33.1 ± 4.5° to 26.7 ± 3.9° (P = 0.0012), and CRP rose from 15.6 ± 2.9° to 24.1 ± 4.2° (P = 0.002). EMG activation declined in key muscles, including Rectus Femoris (0.28 ± 0.05 to 0.23 ± 0.05, P = 0.0035) and Soleus (0.21 ± 0.05 to 0.18 ± 0.04, P = 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 = 0.0012), and Peak Power from 65.7 ± 6.03 to 50.4 ± 4.95 W kg-1 (P < 0.0001).

Fatigue in the final sprint phase significantly impairs joint coordination, muscle activation, and power output. These findings highlight the need for targeted fatigue-resistance training and individualized recovery protocols. A limitation is the all-male sample, which may affect generalizability.