The design and test of a micropower signal conditioning circuit for a piezoresistive accelerometer is presented. The circuit is intended for sensing human body motion in rateadaptive cardiac pacemakers. A strategy is proposed to allow to handle the piezoresistive sensor with the desired level of consumption. Experimental results show the fabricated circuit is able to measure accelerations in the range from 0.04g to 0.34g with a total consumption of less than 3mA with supply voltages down to 2V.