The primary objective of this study funded by the Pittsburgh Claude D. Pepper Older Americans Independence Center was to use musculoskeletal computational modeling techniques to investigate the influence of aging on lower extremity muscle contributions and coordination during anticipatory postural adjustments. Subjects performed a stepping task that included simple step reaction time trials where subjects were asked to step as quickly as possible to a location forward with one foot, in response to an auditory cue. Subjects had knowledge of the step location prior to each auditory cue. Our modeling approach was to conduct muscle-driven forward dynamics simulations based upon optimum tracking techniques common in musculoskeletal modeling using captured experimental data.