Both postural and startle responses rapidly habituate with repeated exposures to the same stimulus and the first exposure to a seated forward acceleration elicits a startle response in the neck muscles. Our goal was to examine how the acoustic startle response is integrated with the habituated neck postural response elicited by forward accelerations of seated subjects. In Experiment 1, 14 subjects underwent 11 sequential forward accelerations followed by 5 additional sled accelerations combined with a startling tone (124dB SPL) initiated 18 ms after sled acceleration onset. During the acceleration-only trials, changes consistent with habituation occurred in the RMS amplitude of the neck muscles and in the peak amplitude of five head and torso kinematic variables. The subsequent addition of the startling tone restored the amplitude of the neck muscles and four of the five kinematic variables, but shortened muscle onset times by 9 to 12ms. These shortened onset times were further explored in Experiment 2, wherein 16 subjects underwent 11 acceleration-only trials followed by 15 combined acceleration/tone trials with varying interstimulus delays (0, 13, 18, 23, 28ms). Onset times shortened further for the 0 and 13ms delay conditions, but did not lengthen for the 23 and 28ms delays. These temporal and spatial changes in EMG can be explained by a summation of the excitatory drive converging at or before the neck muscle motoneurons. The present observations suggest that habituation to repeated sled accelerations involves the extinguishing the startle response and tuning the postural response to the whole-body disturbance.