Anterior and posterior reactive postural responses in healthy elderly and Parkinson disease

Postural instability in Parkinson disease (PD) results in coordination deficits that contribute to a high incidence of falls (>; 70% fall each year, 13% fall >; once per week). To investigate the characteristics of reactive postural responses in PD, we examined lower extremity biomechanical variables during induced anterior and posterior falls. Ten males with mild to moderate PD (mean age=68.7±6.9 y) on medications, and 10 healthy male controls (mean age =66.8± 6.3 y) underwent motion analysis laboratory measurement of the following kinematic variables: reaction time, step length, step time, peak center of mass (COM) velocity, and recovery time. Anteriorly and posteriorly directed reactive responses were provoked through falls generated with an electromagnetic tether‐release system. Between group comparisons were performed using separate Mann‐Whitney U tests (p≤0.01). During anterior falls, PD subjects demonstrated decreased step length (p<.01) and decreased peak COM velocity (p<.01). No significant differences were found for posterior falls. In this study, PD subjects demonstrated hypokinetic and bradykinetic (decreased and slowed) reactive responses (anterior >; posterior) during falls compared to controls. Future research is necessary to clarify the effects of therapeutic interventions (rehabilitation, medication, surgery) on reactive responses and falls in PD. Grant Funding Source : Univ. of Utah College of Health