Background <p>Muscle spasticity, impaired coordination and fatigue are common in cerebral palsy (CP) children. This study investigated frequency-specific effects of focal muscle vibration (FMV) on neuromuscular activation, fatigue, and agonist–antagonist coordination. We hypothesized that 8 weeks of FMV would improve lower limb muscle activation, reduce fatigue, and optimize co-contraction compared to control, with differential effects between 80 and 100 Hz stimulation.</p> Methods <p>In a double-blind randomized controlled trial, 65 spastic diplegic CP children (GMFCS II–IV) were allocated to Control, 80 Hz, or 100 Hz FMV groups. Primary outcomes were EMG-derived muscle activation (RMS) and fatigue (median frequency; and fatigue index). Secondary outcomes included co-contraction index (CCI) between tibialis anterior (TA) and soleus (Sol). Assessments were conducted at baseline, 4, 8, and 12 weeks. Linear mixed-effects models evaluated Group, Time, and Group × Time effects, with Bonferroni-corrected post-hoc comparisons.</p> Results <p>Significant group differences were observed primarily in the TA. In non-dominant leg, the 100 Hz group showed higher RMS compared to Control at 4 weeks (<i>p</i> = 0.027) and 8 weeks (<i>p</i> = 0.027) and compared to 80 Hz at 4 weeks (<i>p</i> = 0.045) and 8 weeks (<i>p</i> = 0.008). In dominant leg, 100 Hz also demonstrated higher RMS than Control at 8 weeks (<i>p</i> = 0.003). Fatigue analysis revealed significant time effects in soleus muscle (<i>p</i> ≤ 0.009), with 100 Hz group demonstrating more sustained MDF values in the dominant limb, suggesting improved fatigue resistance, whereas 80 Hz group showed greater fatigue-related declines. FI analysis further revealed significant Group × Time interactions in non-dominant Sol (<i>p</i> = 0.008), with 80 Hz differing from Control (<i>p</i> = 0.019) and 100 Hz (<i>p</i> = 0.008) at 8 weeks. For co-contraction, a significant group effect was observed in the non-dominant limb (<i>p</i> = 0.034), indicating differences between intervention and control groups, although post-hoc comparisons were not significant.</p> Conclusion <p>FMV induces frequency-specific neuromuscular adaptations in CP children. 100 Hz stimulation appears more effective for enhancing short-term muscle activation and fatigue resistance, while 80 Hz may promote longer-term coordination changes.</p> <p><i>Trial registration</i> Trial prospectively registered with United States clinical trial registry (clinicaltrials.gov), trial ID: NCT05751135.</p>