Characterizing Stair Ambulation Kinetics and the Effects of Dual Tasking in Parkinson's Disease

Abstract

Background: Stair ambulation is a complex motor task that presents a substantial fall risk for people with Parkinson's disease (PwPD) who often have postural instability and gait difficulty (PIGD) and experience unpredictable freezing of gait (FOG) episodes. While dual-task (DT) interference during level walking is well-documented, its impact on stair ambulation, an everyday, high-risk activity, remains poorly understood. Objective: The aim of this study was to quantify the impact of dual tasking on patterns of motor control during stair ambulation using kinetic data from The Stair Ambulation and Functional Evaluation of Gait (Safe-Gait) system. Methods: Seventeen individuals with Parkinson's disease (PD) completed three single-task (ST) and three dual-task (DT) trials on the Safe-Gait system, which sampled kinetic data via embedded force plates during stair ascent and descent. The force plate data were used to quantify step time, braking and propulsive impulses, and center of pressure (CoP) displacement and sway speed to assess DT effects on stair ambulation kinetics. Results: Dual-task conditions led to significant increases in step time (p < 0.001), braking impulse (p < 0.01), anteroposterior center of pressure (CoP) range (p < 0.05), and a decrease in mediolateral CoP speed (p < 0.01). Conclusions: Dual tasking during stair ambulation altered gait kinetics in PwPD, evidenced by slower, less stable movement patterns. These findings highlight the impact of cognitive motor DT interference on functional mobility and support the use of instrumented stair assessments to guide therapeutic care and fall risk interventions.

Keywords: Parkinson’s disease; gait biomechanics; postural instability and gait difficulties; stair ambulation.

Figure 1

The Stair Ambulation and Functional Evaluation of Gait (Safe-Gait) platform consists of three standard steps and a 4 m flat surface, with reinforced handrails. It integrates force plates and photoelectric timing gates for comprehensive functional mobility assessment. Phases of the task are segmented by the three photoelectric timing gates (red beams): gates 1 and 2 for stair ascent and descent phases, gates 2 and 3 for walk-out and walk-back phases, and gate 3 for the turning phase.

Figure 2

Anteroposterior ground reaction forces and impulse profiles during stair ambulation were impacted by dual-task conditions. Mean normalized AP force trajectories (N/kg) are shown for single-task (solid lines) and dual-task (dashed lines) conditions during stair ascent (top) and descent (bottom), plotted across step time (%). Shaded areas represent braking (red) and propulsive (green) impulses. Dual-task conditions resulted in greater braking impulse.