This paper presents a study of the impact of mobility on the distance estimation between 2 nodes of a Wireless Body Area Network (WBAN) by comparing the Two-Way Ranging (2WR) and Three-Way Ranging (3WR) protocols. We consider a WBAN using a typical TDMA-based Medium Access Control (MAC) protocol and a IR-UWB physical layer defined by the standard IEEE802.15.6. We represent the impact by using the Root Mean Square Error (RMSE) in function of two types of parameters, the speed and the time of response. The results show that depending on the speed and the chosen reference point, it is better chose 2WR or 3WR if only mobility is considered. Finally, we propose to extend the study with a joint mobility and clock drift scenario with more sophisticated techniques such as cooperative scheduling algorithms or Aggregated and Broadcast mechanisms.