Preparation of anticipatory postural adjustments prior to stepping

Colum D. MacKinnon*, Dennis Bissig, Julie Chiusano, Emily Miller, Laura Rudnick, Candice Jager, Yunhui Zhang, Marie Laure Mille, Mark W. Rogers

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

169 Scopus citations


Step initiation involves anticipatory postural adjustments (APAs) that propel the body mass forward and laterally before the first step. This study used a startle-like acoustic stimulus (SAS) and transcranial magnetic stimulation (TMS) to examine the preparation of APAs before forward stepping. After an instructed delay period, subjects initiated forward steps in reaction to a visual "go" cue. TMS or SAS was delivered before (-1,400 or -100 ms), on (0 ms), or after (+100 ms for TMS, +200 ms for SAS) the imperative "go" cue. Ground reaction forces and electromyographic activity were recorded. In control trials, the mean reaction time was 217 ± 38 ms. In contrast, the SAS evoked APAs that had an average onset of 110 ± 54 ms, whereas the incidence, magnitude, and duration of the APA increased as the stimulus timing approached the "go" cue. A facilitation of motor-evoked potentials in the initial agonist muscle was observed only when TMS was applied at +100 ms. These findings indicate that there was an initial phase of movement preparation during which the APA-stepping sequence was progressively assembled, and that this early preparation did not involve the corticomotor pathways activated by TMS. The subsequent increase in corticomotor excitability between the imperative stimulus and onset of the APA suggests that corticospinal pathways contribute to the voluntary initiation of the prepared APA-stepping sequence. These findings are consistent with a feedforward mode of neural control whereby the motor sequence, including the associated postural adjustments, is prepared before voluntary movement.

Original languageEnglish (US)
Pages (from-to)4368-4379
Number of pages12
JournalJournal of neurophysiology
Issue number6
StatePublished - Jun 2007

ASJC Scopus subject areas

  • General Neuroscience
  • Physiology


Dive into the research topics of 'Preparation of anticipatory postural adjustments prior to stepping'. Together they form a unique fingerprint.

Cite this