Objectives: This prospective pilot study in healthy children aimed to evaluate the effect of whole-body vibration therapy (WBVT) on hip girdle muscle activation and identify the optimal amplitude and frequency settings that replicate the effects of walking or running without causing discomfort. Methods: A prospective pilot study involving 20 healthy children was conducted to evaluate muscle activation during WBVT at amplitudes of 1, 2, and 3 mm and frequencies of 5–20 Hz. Surface electromyography of the gluteus medius, tensor fascia lata, iliopsoas, and rectus femoris was recorded during walking, running, and WBVT trials, and steady-state 10-s epochs were extracted for analysis. Results: Although dose–response analyses showed no statistically significant increases beyond 10 Hz within WBVT conditions, the reported thresholds specify the vibration settings at which WBVT-induced activation exceeded the RMS values observed during walking or running, rather than indicating significant within-WBVT frequency differences. When “optimal setting” was defined as the highest activation within tolerable ranges, the 3 mm/ 10 Hz setting met these criteria. Conclusions: WBVT produced short-term increases in hip-girdle muscle activation under tolerable conditions. While not indicative of therapeutic benefit, these data provide hypothesis-generating insights for future clinical studies involving children with movement limitations.