Abstract In a seated posture into an autovehicle, humans are most sensitive to whole‐body vibrations under low‐frequency excitation. This research is focused only on the effect of the backrest angle on the biodynamic response functions. In this paper there are present the results of investigations for 10 participants, whose mean body mass was 61.4 kg. For the biodynamic responses of a seated human body subjected to vertical vibrations, three automotive postures was study: without backrest support, with backrest inclined 7° and respectively 15°, by measurement of transmitted vibration in two different situations: with belt and respectively without this. Knowledge of human responses to vibration provides information about the position of backrest support to mitigate vibration transmitted through the body ensuring the health, comfort and performance. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)