Ozell Sanders, Ph.D.


Physical Rehabilitation Science

Area of Doctoral Study: Physical Rehabilitation

Undergraduate Institute: University of Maryland, Baltimore County

Research Advisor: Mark W. Rogers, PT, Ph.D, FAPTA

Description of Research

We have been investigating the effects of neuromotor and biomechanical impairments associated with aging. Specifically we are interested in how these deficits compromise standing balance stability and precipitate falls. We and others have noticed that unpracticed or unexpected balance disturbances are frequently startling events that may often result in a fall. This rapid and exaggerated startle-like reaction incorporated into the balance stabilizing response in association with the tendency to fall appear to diminish with repeated exposures due to behavioral habituation. Thus, the term ‘first-trial reaction’ (FTR) describes the initial inexperienced, exaggerated startle-like balance disturbance response. It is striking that FTRs are commonly seen for any sudden event that disturbs standing balance such as we observe in the parent project (e.g. pulls, pushes, slips, trips, collisions). To date, falls research has mainly focused on balance responses that stabilize the body in the forward-backward or sideways directions, i.e. horizontally. Yet, all events that disrupt balance and cause falling share the common universal element of downward motion of the body under the force of gravity. Limited data from studies of human free falls show rapid and exaggerated muscle activation FTRs which resemble the generalized muscle activity evoked by other strong sensory stimuli such as a loud sound that triggers a startle reaction. If the FTR to free fall is characteristic of the initial responses to other common threats to balance experienced during daily activities then it is important to better understand whether or not this reaction normally represents a protective anti-gravity response against collapse, or incorporates a startle response that may interfere with balance recovery. This information would help to inform understanding about whether a fall induced startle incorporated together with an antigravity balance response either enhances balance recovery or is problematic for it. Furthermore, the extent to which the free fall FTR is changed with older age would be important to determine since both balance responses and generalized startle responses show age-related differences. Concerning the increased risk of falling with advancing age, it would also be important to know the extent to which an increased tendency to experience falls may be linked with FTR profiles and startle reactions. If that is the case, then we may be able to establish a mechanistically grounded, innovative, and technically simpler clinical assessment tool than currently used balance testing devices for identifying fall risk among older individuals. Moreover, novel and effective rehabilitation exercise and behavioral approaches to minimize disruptive FTR reactions may be guided by the findings from this line of research.