Abstract : Whole-body vibration (WBV) has been shown to result in augmented muscle activity during the exposure to the vibration, which has been assessed with surface electromyography (sEMG). While numerous studies have focused on the evaluation of the optimal training parameters using sEMG recordings during WBV, its validity is still debated. Briefly, excessive peaks at the vibration frequency and its multiple harmonics are displayed in the sEMG frequency spectrum. Unfortunately, only a few studies have addressed this issue, and to date it is not clear whether the spikes observed in the frequency domain during WBV arise from stretch reflexes (Ritzmann et al., 2010), motion artifacts (Fratini et al., 2009), or both (Sebik et al., 2012). Therefore, the aim of this study was to gain insight about the origin of these excessive peaks by analyzing sEMG signals from muscles and signals from dummy electrodes placed on the patella. It was hypothesized that (1) motion artifacts are observed in the patella signal at the vibration frequency and its multiple harmonics during WBV, and that (2) the sEMG of the spikes is linearly related to the sEMG without the spikes.