Short-Term Effects of Single-Session Split-Belt Treadmill Training on Dual-Task Performance in Parkinson's Disease and Healthy Elderly

Background: Dual-tasking is challenging for people with Parkinson's disease and freezing of gait (PD+FOG) and can exacerbate freezing episodes and falls. Split-belt treadmill training (SBT) is a novel tool to train complex gait and may improve dual-task (DT) walking and turning. Objective: To investigate the single-session effects of SBT on DT walking and DT turning performance in PD+FOG and older adults (OA), compared to regular treadmill training. Methods: Forty-five PD+FOG and 36 OA participated in a single training session (30 min). They were randomized into one of four training groups: (A) SB75—steady belt speed ratio 0.75:1; (B) SB50—steady belt speed ratio 0.5:1; (C) SBCR—changing belt speed ratios between 0.75:1 and 0.5:1; and (D) Tied-Belt (TBT). Over-ground straight-line gait and an alternating turning in place task combined with a cognitive dual-task (DT) (auditory Stroop) were assessed pre- and post-training, and the following day (retention). Constrained longitudinal data analysis was used to investigate the training effects for all participants and for PD+FOG alone. Results: DT gait speed improved at post-training for all groups (p < 0.001). However, SBT (SB50 and SBCR) led to larger post-training improvements compared to TBT, which were still visible at retention (SB50). For mean DT turning speed and Stroop response time while walking, only SBT groups showed significant improvements at post-training or retention. DT stride length, peak DT turning speed, and Stroop performance index while walking also showed larger gains in SBT compared to TBT. Results for PD+FOG alone showed similar effects although with smaller effect sizes. Conclusions: A single session of SBT in PD+FOG and OA showed larger short-term effects on DT walking and turning compared to TBT. Cognitive DT performance was also improved in SBT, likely due to reduced cortical control of gait. These results illustrate the potential for SBT to improve DT during complex gait and possibly reduce fall risk in clinical and healthy populations.status: Published onlin

Words that move us.: The effects of sentences on body sway

According to the embodied cognition perspective, cognitive systems and perceptuo-motor systems are deeply intertwined and exert a causal effect on each other. A prediction following from this idea is that cognitive activity can result in subtle changes in observable movement. In one experiment, we tested whether reading various sentences resulted in changes in postural sway. Sentences symbolized various human activities involving high, low, or no physical effort. Dutch participants stood upright on a force plate, measuring the body center of pressure, while reading a succession of sentences. High physical effort sentences resulted in more postural sway (greater SD) than low physical effort sentences. This effect only showed up in medio-lateral sway but not anterio-posterior sway. This suggests that sentence comprehension was accompanied by subtle motoric activity, likely mirroring the various activities symbolized in the sentences. We conclude that semantic processing reaches the motor periphery, leading to increased postural activity

The New Freezing of Gait Questionnaire: Unsuitable as an Outcome in Clinical Trials?

Background: Freezing of gait (FOG) is a common gait deficit in Parkinson's disease. The New Freezing of Gait Questionnaire (NFOG-Q) is a widely used and valid tool to quantify freezing of gait severity. However, its test-retest reliability and minimal detectable change remain unknown. Objective: To determine the test-retest reliability and responsiveness of the NFOG-Q. Methods: Two groups of freezers, involved in 2 previous rehabilitation trials, completed the NFOG-Q at 2 time points (T1 and T2), separated by a 6-week control period without active intervention. Sample 1 (N = 57) was measured in ON and sample 2 (N = 14) in OFF. We calculated various reliability statistics for the NFOG-Q scores between T1 and T2 as well as correlation coefficients with clinical descriptors to explain the variability between time points. Results: In sample 1 the NFOG-Q showed modest reliability (intraclass correlation coefficient = 0.68 [0.52-0.80]) without differences between T1 and T2. However, a minimal detectable change of 9.95 (7.90-12.27) points emerged for the total score (range 28 points, relative minimal detectable change of 35.5%). Sample 2 showed largely similar results. We found no associations between cognitive-related or disease severity-related outcomes and variability in NFOG-Q scores. Conclusions: We conclude that the NFOG-Q is insufficiently reliable or responsive to detect small effect sizes, as changes need to go beyond 35% to surpass measurement error. Therefore, we warrant caution in using the NFOG-Q as a primary outcome in clinical trials. These results emphasize the need for robust and objective freezing of gait outcome measures.status: publishe

Lower back muscle activity during weight-shifting is affected by ageing and dual-tasking

Purpose: Postural control deteriorates with age, especially under dual-task conditions. It is currently unknown how a challenging virtual reality weight-shifting task affects lower back muscle activity. Hence, this study investigated erector spinae neuromuscular control during mediolateral weight-shifting as part of an exergame during single- (ST) and dual-task (DT) conditions in young and older adults. Methods: Seventeen young and 17 older adults performed mediolateral weight-shifts while hitting virtual wasps in a virtual environment with and without a serial subtraction task (DT). Center of mass position was recorded in real-time using 3D motion capturing. Electromyography recorded bilateral activation of the lumbar longissimus and iliocostalis muscles. Results: Weight-shifting (p < 0.03) and targeting the wasps (p < 0.005) deteriorated with age and DT. Relative muscle activation during both quiet stance and weight-shifting increased with age, while the DT-effect did not differ consistently between age-groups. However, bilateral muscle co-contraction decreased with DT in young adults only. When switching direction and targeting the wasps, variability of muscle activation increased with age and DT and proved related to worse targeting performance. These effects were mainly visible at the non-dominant body side. Conclusion: Older adults showed a higher erector spinae muscle contribution to perform weight-shifts with increased variability at the end of a shift, whereby muscle activity was modulated less well in older than in young adults in response to DT. Hence, the current findings point to the potential for developing postural training in which older adults learn to fine-tune trunk muscle activity to improve weight-shifting and reduce fall risk