In Parkinson's disease, dual-tasking reduces gait smoothness during the straight-walking and turning-while-walking phases of the Timed Up and Go test

Abstract

Background: Dual-task walking is used as a treatment, for gait assessment, and as an outcome measure in Parkinson's disease (PD). Movement smoothness, i.e. its non-intermittency, is a movement cardinal feature. This study assesses whether dual-tasking reduces gait smoothness in PD alongside reducing speed, one of its well-known effects.

Methods: The Timed Up and Go (TUG) test, instrumented with an inertial sensor fixed to the back, was administered to 33 PD patients (15 females; age: median = 71 years; IQR = 10) to assess two walking types: straight-walking and turning-while-walking. The TUG test was completed in single-task and two dual-task modalities: cognitive (doing successive subtractions) and motor (holding a water glass). The angular speed spectral arc length metric (SPARC) and the Ln-DimensionLess Jerk (LDLJ), two smoothness measures quantifying the peaks and dips in the speed profile, were measured, along with the trunk angular velocity and the foot strikes number. ANOVA was used for hypothesis testing and estimated marginal means for post-hoc tests and effect sizes (ES).

Results: In straight-walking and turning, cognitive and motor dual tasks decreased gait speed (ES range = [0.476, 1.379]; p < 0.01) and increased the step number (ES = [0.402, 0.927]; p < 0.05). SPARC (ES = [0.221, 0.493]; p < 0.05) and angular LDLJ (ES = [0.451, 0.929]; p < 0.01) were lower in the two dual-task conditions in both phases, indicating reduced gait smoothness than in single-task. This worsening of gait smoothness was partially confirmed after ruling out the dual-task effect on speed and step number. In particular, anterior-posterior SPARC during turning was still low in cognitive (ES = 0.351; p < 0.01) and motor (ES = 0.283; p < 0.05) dual tasks.

Conclusions: In PD, dual-tasking decreases gait speed and increases the step number when walking straight and turning while walking. Independently of these effects, dual-tasking also reduces gait smoothness. As an independent feature of movement, when dual-task walking is the outcome measure, improving smoothness may represent a novel treatment aim in PD. As long as it is instrumented with an inertial sensor, the TUG test is valuable for studying different walking types.

Trial registration: NCT05904171 (ClinicalTrials.gov; date registration: 2023-06-06).

Keywords: Dual-task; Gait analysis with inertial sensors; Gait smoothness; Inertial measurement unit; Instrumented Timed Up and Go test; Neurological rehabilitation; Parkinson's disease; Tremor, ataxia, hyperkinetic movement disorder.

Fig. 1

Low and high gait smoothness from the Timed Up and Go test: representative examples. Trunk anterior-posterior speed (upper panel) during the turning-while-walking phase of the Timed Up and Go test is shown for two patients, one with low (A) and another with high (B) smoothness of gait. Data are from two representative test repetitions matched for trunk speed root mean square (A: 35.1 °/s; B: 35.0 °/s), turning duration (A: 2.2 s; B: 2.7 s) and foot strike number (four for both). Speed offset was removed for this figure for graphical reasons. Middle panel: magnitude spectrum. Arrows mark the upper frequency for SPARC calculation. The horizontal continuous line is set at 0.05. Lower panel: squared anterior-posterior angular jerk (LDLJ_angular). At visual inspection of the speed traces (upper panel), it is apparent that there are more peaks and dips in the anterior-posterior speed profile in A than in B. More precisely, A has brisker and larger speed changes leading to steep-sided, sharp-pointed peaks, like the one indicated by the arrowhead. These more pronounced speed changes lead to an increased arc length of the speed spectrum (i.e. lower SPARC) and a larger area under the curve of the squared jerk (i.e. lower LDLJ)

Fig. 2

Gait speed and smoothness metrics in single, cognitive and motor dual-task: walking phase of the Timed Up and Go test. Black point graphs: estimated marginal means and their 95% confidence intervals (CI) from the interaction of the task condition and the measurement axis (i.e. mean values for each axis and task combination). White point graphs: estimated marginal means and 95% CI for the three task conditions (i.e. mean values given the task and irrespectively of the axis of measurement); white point graphs are reported only in the case of ANOVA reporting a significant task factor and insignificant interaction between task and axis. Walking: walking phase of the Timed Up and Go (TUG) test. Speed RMS: root mean square (RMS) of the trunk angular speed; SPARC: spectral arc length measure calculated from the trunk angular velocity; LDLJ: ln-dimensionless jerk from the linear acceleration (LDLJ_linear) or the angular acceleration (LDLJ _angular); Vert, ML, AP: vertical, mediolateral and anterior-posterior measurement axis. Single: single-task modality; Cog: cognitive dual-task; Mot: motor dual-task. SPARC and LDLJ are dimensionless (1). The black horizontal dashed lines mark the measures from the single-task modality. *: cognitive or motor dual tasks significantly differ from the single-task modality. °: cognitive and motor dual tasks are significantly different from each other

Fig. 3

Gait speed and smoothness metrics in single, cognitive and motor dual-task: turning phase of the Timed Up and Go test. Same abbreviations as Fig. 2

Fig. 4

Correlation between gait speed, gait smoothness and executive functions. Single, Cognitive, Motor: single task modality, cognitive and motor dual-task; AP: anterior-posterior; RMS: root mean square; SPARC: spectral arc length measure (dimensionless, 1); FAB: Frontal Assessment Battery. The FAB scores are split into < and ≥ the median (vertical dashed line). Rho: Spearman’s rho; p: p-value of the Spearman correlation. The boxplots show the speed and SPARC values in the participants’ sample split according to the median FAB value to make the association between walking metrics and executive functions more apparent