A Data-Driven Framework for Direct Local Tensile Property Prediction of Laser Powder Bed Fusion Parts.

This article proposes a generalizable, data-driven framework for qualifying laser powder bed fusion additively manufactured parts using part-specific in situ data, including powder bed imaging, machine health sensors, and laser scan paths. To achieve part qualification without relying solely on statistical processes or feedstock control, a sequence of machine learning models was trained on 6299 tensile specimens to locally predict the tensile properties of stainless-steel parts based on fused multi-modal in situ sensor data and a priori information. A cyberphysical infrastructure enabled the robust spatial tracking of individual specimens, and computer vision techniques registered the ground truth tensile measurements to the in situ data. The co-registered 230 GB dataset used in this work has been publicly released and is available as a set of HDF5 files. The extensive training data requirements and wide range of size scales were addressed by combining deep learning, machine learning, and feature engineering algorithms in a relay. The trained models demonstrated a 61% error reduction in ultimate tensile strength predictions relative to estimates made without any in situ information. Lessons learned and potential improvements to the sensors and mechanical testing procedure are discussed.

Remote Delivery of Allied Health Therapies in Parkinson's Disease.

Remote delivery of allied health therapies has long been possible, but adoption has been limited in some disciplines until relatively recently. The COVID-19 pandemic drove dramatic increases in use of remote delivery within allied health. This review summarizes the latest evidence on remotely-delivered physical therapy, occupational therapy, and speech therapy and discusses associated challenges and opportunities.

Ultrafast X-Ray Scattering Reveals Composite Amplitude Collective Mode in the Weyl Charge Density Wave Material (TaSe_{4})_{2}I.

We report ultrafast x-ray scattering experiments of the quasi-1D charge density wave (CDW) material (TaSe_{4})_{2}I following ultrafast infrared photoexcitation. From the time-dependent diffraction signal at the CDW sidebands we identify a 0.11 THz amplitude mode derived primarily from a transverse acoustic mode of the high-symmetry structure. From our measurements we determine that this mode interacts with the valence charge indirectly through another collective mode, and that the CDW system in (TaSe_{4})_{2}I has a composite nature supporting multiple dynamically active structural degrees of freedom.

Natural Walking Intensity in Persons With Parkinson Disease.

BACKGROUND AND PURPOSE: Few persons with Parkinson disease (PD) appear to engage in moderate-intensity walking associated with disease-modifying health benefits. How much time is spent walking at lower, yet still potentially beneficial, intensities is poorly understood. The purpose of this exploratory, observational study was to describe natural walking intensity in ambulatory persons with PD. METHODS: Accelerometer-derived real-world walking data were collected for more than 7 days at baseline from 82 participants enrolled in a PD clinical trial. Walking intensity was defined according to the number of steps in each active minute (1-19, 20-39, 40-59, 60-79, 80-99, or ≥100 steps). Daily minutes of walking and duration of the longest sustained walking bout were calculated at each intensity. Number of sustained 10 to 19, 20 to 29, and 30-minute bouts and greater at any intensity also were calculated. Values were analyzed in the context of physical activity guidelines. RESULTS: Most daily walking occurred at lower intensities (157.3 ± 58.1 min of 1-19 steps; 81.3 ± 32.6 min of 20-39 steps; 38.2 ± 21.3 min of 40-59 steps; 15.1 ± 11.5 min of 60-79 steps; 7.4 ± 7.0 min of 80-99 steps; 7.3 ± 9.6 min of ≥100 steps). The longest daily sustained walking bout occurred at the lowest intensity level (15.9 ± 5.2 min of 1-19 steps). Few bouts lasting 20 minutes and greater occurred at any intensity. DISCUSSION AND CONCLUSIONS: Despite relatively high daily step counts, participants tended to walk at remarkably low intensity, in bouts of generally short duration, with relatively few instances of sustained walking. The findings reinforced the need for health promotion interventions designed specifically to increase walking intensity.Video Abstract available for more insight from authors (see the Video, Supplemental Digital Content 1 available at: http://links.lww.com/JNPT/A426 ).

Observation of a massive phason in a charge-density-wave insulator.

The lowest-lying fundamental excitation of an incommensurate charge-density-wave material is believed to be a massless phason-a collective modulation of the phase of the charge-density-wave order parameter. However, long-range Coulomb interactions should push the phason energy up to the plasma energy of the charge-density-wave condensate, resulting in a massive phason and fully gapped spectrum1. Using time-domain terahertz emission spectroscopy, we investigate this issue in (TaSe4)2I, a quasi-one-dimensional charge-density-wave insulator. On transient photoexcitation at low temperatures, we find the material strikingly emits coherent, narrowband terahertz radiation. The frequency, polarization and temperature dependences of the emitted radiation imply the existence of a phason that acquires mass by coupling to long-range Coulomb interactions. Our observations underscore the role of long-range interactions in determining the nature of collective excitations in materials with modulated charge or spin order.

Prospective associations between accelerometry-derived physical activity and sedentary behaviors and mortality among cancer survivors.

BACKGROUND: Survival benefits of self-reported recreational physical activity (PA) during cancer survivorship are well-documented in common cancer types, yet there are limited data on the associations between accelerometer-derived PA of all domains, sedentary behavior, and mortality in large, diverse cohorts of cancer survivors. METHODS: Participants included adults who reported a cancer diagnosis in the National Health and Nutrition Examination Survey and wore an accelerometer for up to 7 days in 2003-2006. Participants were followed for subsequent mortality through 2015. We examined the association of light PA, moderate to vigorous PA, total PA, and sedentary behavior, with all-cause mortality. Cox proportional hazards models estimated hazard ratios (HRs) and 95% confidence intervals (CIs), adjusting for demographics and health indicators. RESULTS: A total of 480 participants (mean age of 68.8 years [SD = 12.4] at the time of National Health and Nutrition Examination Survey assessment) reported a history of cancer. A total of 215 deaths occurred over the follow-up period. For every 1-h/d increase in light PA and moderate to vigorous PA (MVPA), cancer survivors had 49% (HR = 0.51, 95% CI = 0.34 to 0.76) and 37% (HR = 0.63 , 95% CI = 0.40 to 0.99) lower hazards of all-cause mortality, respectively. Total PA demonstrated similar associations with statistically significantly lower hazards of death for each additional hour per day (HR = 0.68, 95% CI = 0.54 to 0.85), as did every metabolic equivalents of task-hour per day increase in total PA estimations of energy expenditure (HR = 0.88, 95% CI = 0.82 to 0.95). Conversely, more sedentary time (1 h/d) was not associated with statistically significantly higher hazards (HR = 1.08, 95% CI = 0.94 to 1.23). CONCLUSIONS: These findings reinforce the current recommendations for cancer survivors to be physically active and underscore the continued need for widespread PA promotion for long-term survival in older cancer survivors.

Does clinically measured walking capacity contribute to real-world walking performance in Parkinson's disease?

OBJECTIVE: The study examined how clinically measured walking capacity contributes to real-world walking performance in persons with Parkinson's disease (PD). METHODS: Cross-sectional baseline data (n = 82) from a PD clinical trial were analyzed. The 6-Minute Walk Test (6MWT) and 10-Meter Walk Test (10MWT) were used to generate capacity metrics of walking endurance and fast gait speed, respectively. An activity monitor worn for seven days was used to generate performance metrics of mean daily steps and weekly moderate intensity walking minutes. Univariate linear regression analyses were used to examine associations between each capacity and performance measure in the full sample and less and more active subgroups. RESULTS: Walking capacity significantly contributed to daily steps in the full sample (endurance: R2=.13, p < .001; fast gait speed: R2=.07, p = .017) and in the less active subgroup (endurance: R2 =.09, p = .045). Similarly, walking capacity significantly contributed to weekly moderate intensity minutes in the full sample (endurance: R2=.13, p < .001; fast gait speed: R2=.09, p = .007) and less active subgroup (endurance: R2 = .25, p < .001; fast gait speed: R2 =.21, p = .007). Walking capacity did not significantly contribute to daily steps or moderate intensity minutes in the more active subgroup. CONCLUSIONS: Walking capacity contributed to, but explained a relatively small portion of the variance in, real-world walking performance. The contribution was somewhat greater in less active individuals. The study adds support to the idea that clinically measured walking capacity may have limited benefit for understanding real-world walking performance in PD. Factors beyond walking capacity may better account for actual walking behavior.

Musculoskeletal pain in Parkinson's disease: a narrative review.

The prevalence of musculoskeletal (MSK) pain in people with Parkinson's disease (PD) is higher than that of age-matched controls. In this review, we outline what is known about MSK pain in PD, focusing on the neck, shoulder, knee, hip and low back. We also compare what is known about MSK pain in PD to what is known in older adults without PD. Finally, we outline areas of for future research related to MSK pain in people with PD.

Lay abstract Joint pain in people with Parkinson's disease (PD) is more common than other healthy older adults. In this paper, we describe what is known about joint pain in PD, focusing on the neck, shoulder, knee, hip and low back. We also compare how much is known about pain in PD versus how much is known about pain in older adults without PD. Finally, we suggest ways future researchers can help the world better understand pain in PD.

Are Mobile Persons With Parkinson Disease Necessarily More Active?

BACKGROUND AND PURPOSE: Walking activity in persons with Parkinson disease (PD) is important for preventing functional decline. The contribution of walking activity to home and community mobility in PD is poorly understood. METHODS: Cross-sectional baseline data (N = 69) were analyzed from a randomized controlled PD trial. The Life-Space Assessment (LSA) quantified the extent, frequency, and independence across 5 expanding levels of home and community mobility, producing individual subscores and a total score. Two additional summed scores were used to represent mobility within (Levels 1-3) and beyond (Levels 4-5) neighborhood limits. An accelerometer measured walking activity for 7 days. Regression and correlation analyses evaluated relationships between daily steps and mobility scores. Mann-Whitney U tests secondarily compared differences in mobility scores between the active and sedentary groups. RESULTS: Walking activity contributed significantly to the summed Level 1-3 score (ß = 0.001, P = 0.004) but not to the summed Level 4-5 (ß = 0.001, P = 0.33) or total (ß = 0.002, P = 0.07) scores. Walking activity was significantly related to Level 1 (ρ = 0.336, P = 0.005), Level 2 (ρ = 0.307, P = 0.010), and Level 3 (ρ = 0.314, P = 0.009) subscores. Only the summed Level 1-3 score (P = 0.030) was significantly different between the active and sedentary groups. DISCUSSION AND CONCLUSIONS: Persons with PD who demonstrated greater mobility beyond the neighborhood were not necessarily more active; walking activity contributed more so to home and neighborhood mobility. Compared with LSA total score, the Level 1-3 summed score may be a more useful participation-level measure for assessing the impact of changes in walking activity.Video Abstract available for more insights from the authors (see the Video, Supplemental Digital Content 1 available at: http://links.lww.com/JNPT/A349).

The Role of Mental Imagery in Parkinson's Disease Rehabilitation.

Parkinson's disease (PD) is a disabling neurodegenerative disease whose manifestations span motor, sensorimotor, and sensory domains. While current therapies for PD include pharmacological, invasive, and physical interventions, there is a constant need for developing additional approaches for optimizing rehabilitation gains. Mental imagery is an emerging field in neurorehabilitation and has the potential to serve as an adjunct therapy to enhance patient function. Yet, the literature on this topic is sparse. The current paper reviews the motor, sensorimotor, and sensory domains impacted by PD using gait, balance, and pain as examples, respectively. Then, mental imagery and its potential for PD motor and non-motor rehabilitation is discussed, with an emphasis on its suitability for addressing gait, balance, and pain deficits in people with PD. Lastly, future research directions are suggested.

Direct observation of large electron-phonon interaction effect on phonon heat transport.

As a foundational concept in many-body physics, electron-phonon interaction is essential to understanding and manipulating charge and energy flow in various electronic, photonic, and energy conversion devices. While much progress has been made in uncovering how phonons affect electron dynamics, it remains a challenge to directly observe the impact of electrons on phonon transport, especially at environmental temperatures. Here, we probe the effect of charge carriers on phonon heat transport at room temperature, using a modified transient thermal grating technique. By optically exciting electron-hole pairs in a crystalline silicon membrane, we single out the effect of the phonon-carrier interaction. The enhanced phonon scattering by photoexcited free carriers results in a substantial reduction in thermal conductivity on a nanosecond timescale. Our study provides direct experimental evidence of the elusive role of electron-phonon interaction in phonon heat transport, which is important for understanding heat conduction in doped semiconductors. We also highlight the possibility of using light to dynamically control thermal transport via electron-phonon coupling.

Effects of Subthalamic Nucleus Deep Brain Stimulation and Levodopa on Balance in People with Parkinson's Disease: A Cross Sectional Study.

Subthalamic nucleus deep brain stimulation (STN-DBS) and levodopa are common treatment strategies for Parkinson's disease (PD). However, the specific effects of these treatment strategies on balance and its components remain unclear. This cross-sectional study of people with PD and STN-DBS compared balance in the treated state (ON-medication/ON-stimulation) and untreated state (OFF-medication/OFF-stimulation) using the Balance Evaluation Systems Test (BESTest). Total BESTest scores from the treated and untreated states were compared to assess overall balance. Scores for the six sections of the BESTest were further compared to assess differences in specific components of balance between treatment conditions. Twenty-nine participants were included (Male: 21, Female: 8, Mean Age ± SD: 65.0 ± 6.9). Total BESTest scores showed improved balance in the treated state compared to the untreated state (Treated: 67.56 ± 10.92; Untreated: 59.23 ± 16.51, p < 0.001). Four sections (Stability Limits/Verticality, Anticipatory Postural Reactions, Sensory Orientation, Stability in Gait) of the BESTest significantly improved in the treated state relative to the untreated state, after correcting for multiple comparisons (p < 0.05). These results demonstrate that STN-DBS and levodopa improve overall balance and provide a first step toward understanding the effects of these treatment strategies on specific components of balance.

Design of the WHIP-PD study: a phase II, twelve-month, dual-site, randomized controlled trial evaluating the effects of a cognitive-behavioral approach for promoting enhanced walking activity using mobile health technology in people with Parkinson-disease.

BACKGROUND: Parkinson disease (PD) is a debilitating and chronic neurodegenerative disease resulting in ambulation difficulties. Natural walking activity often declines early in disease progression despite the relative stability of motor impairments. In this study, we propose a paradigm shift with a "connected behavioral approach" that targets real-world walking using cognitive-behavioral training and mobile health (mHealth) technology. METHODS/DESIGN: The Walking and mHealth to Increase Participation in Parkinson Disease (WHIP-PD) study is a twelve-month, dual site, two-arm, randomized controlled trial recruiting 148 participants with early to mid-stage PD. Participants will be randomly assigned to connected behavioral or active control conditions. Both conditions will include a customized program of goal-oriented walking, walking-enhancing strengthening exercises, and eight in-person visits with a physical therapist. Participants in the connected behavioral condition also will (1) receive cognitive-behavioral training to promote self-efficacy for routine walking behavior and (2) use a mHealth software application to manage their program and communicate remotely with their physical therapist. Active control participants will receive no cognitive-behavioral training and manage their program on paper. Evaluations will occur at baseline, three-, six-, and twelve-months and include walking assessments, self-efficacy questionnaires, and seven days of activity monitoring. Primary outcomes will include the change between baseline and twelve months in overall amount of walking activity (mean number of steps per day) and amount of moderate intensity walking activity (mean number of minutes per day in which > 100 steps were accumulated). Secondary outcomes will include change in walking capacity as measured by the six-minute walk test and ten-meter walk test. We also will examine if self-efficacy mediates change in amount of walking activity and if change in amount of walking activity mediates change in walking capacity. DISCUSSION: We expect this study to show the connected behavioral approach will be more effective than the active control condition in increasing the amount and intensity of real-world walking activity and improving walking capacity. Determining effective physical activity interventions for persons with PD is important for preserving mobility and essential for maintaining quality of life. Clinical trials registration NCT03517371, May 7, 2018. TRIAL REGISTRATION: ClinicalTrials.gov: NCT03517371. Date of registration: May 7, 2018. Protocol version: Original.

Low Back Pain--Related Disability in Parkinson Disease: Impact on Functional Mobility, Physical Activity, and Quality of Life.

BACKGROUND: People with Parkinson disease (PD) frequently experience low back pain (LBP), yet the impact of LBP on functional mobility, physical activity, and quality of life (QOL) has not been described in PD. OBJECTIVE: The objectives of this study were to describe body positions and functional activities associated with LBP and to determine the relationships between LBP-related disability and PD motor sign severity, physical activity level, and QOL. DESIGN: The study was a cross-sectional study. METHODS: Thirty participants with idiopathic PD (mean age = 64.6 years [SD = 10.3]; 15 women) completed the Revised Oswestry Disability Questionnaire (RODQ), a measure of LBP-related disability. PD motor symptom severity was measured using the Movement Disorder Society-Unified Parkinson Disease Rating Scale Part III (MDS-UPRDS III). The Physical Activity Scale for the Elderly (PASE) was used to measure self-reported physical activity. The Parkinson Disease Questionnaire-39 (PDQ-39) was used to measure QOL. Descriptive statistics were used to characterize LBP intensity and LBP-related disability. Spearman correlations were used to determine relationships between the RODQ and the MDS-UPDRS III, PASE, and PDQ-39. RESULTS: LBP was reported to be of at least moderate intensity by 63.3% of participants. LBP most frequently impaired standing, sleeping, lifting, and walking. The RODQ was significantly related to the MDS-UPDRS III (r = 0.38), PASE (r = -0.37), PDQ-39 summary index (r = 0.55), PDQ-39 mobility subdomain (r = 0.54), and PDQ-39 bodily pain subdomain (r = 0.44). LIMITATIONS: Limitations included a small sample of people with mild to moderate PD severity, the fact that RODQ is a less frequently used measure of LBP-related disability, and the lack of a non-PD control group. CONCLUSIONS: LBP affected walking, sleeping, standing, and lifting in this small sample of people with mild to moderate PD. Greater LBP-related disability was associated with greater motor sign severity, lower physical activity level, and lower QOL in people with PD.

Exercise and Parkinson Disease: Comparing Tango, Treadmill, and Stretching.

BACKGROUND AND PURPOSE: Impaired gait, balance, and motor function are common in Parkinson disease (PD) and may lead to falls and injuries. Different forms of exercise improve motor function in persons with PD, but determining which form of exercise is most effective requires a direct comparison of various approaches. In this prospective, controlled trial, we evaluated the impact of tango, treadmill walking, and stretching on gait, balance, motor function, and quality of life. We hypothesized tango and treadmill would improve forward walking and motor symptom severity, and tango would also improve backward walking, balance, and quality of life. METHODS: Ninety-six participants (age: 67.2 ± 8.9 years, 42% female) with mild to moderate idiopathic PD were serially assigned to tango, treadmill walking, or stretching (active control group) and attended 1-hour classes twice weekly for 12 weeks. Assessments occurred OFF anti-PD medication before and after the intervention and at follow-up 12 weeks after the intervention. RESULTS: Forward velocity and backward velocity improved for the treadmill group from baseline to posttest and improvements persisted at follow-up. Backward velocity and motor functioning improved for the stretching group from baseline to posttest, but results did not persist at follow-up. There were no significant changes in the tango group across time points. DISCUSSION AND CONCLUSIONS: Contrary to our hypotheses, only treadmill improved forward walking, while backward walking improved with treadmill and stretching. Future research should examine combinations of exercises with a focus on optimizing dosing and examining whether specific characteristics of people with PD correlate with different types of exercise.Video Abstract available for more insights from the authors (see Video, Supplemental Digital Content 1, available at: http://links.lww.com/JNPT/A237).

Freezing of Gait Boot Camp: feasibility, safety and preliminary efficacy of a community-based group intervention.

AIM: In this pilot study, we evaluated the feasibility, safety and preliminary efficacy of a 6-week, community-based group intervention designed to reduce freezing of gait (FOG) for people with Parkinson's disease (PD). METHODS: Seven people with PD completed 'FOG Boot Camp' provided by the St. Louis Chapter of the American Parkinson Disease Association. We recorded attendance, participant's acceptance of the intervention and adverse events during classes. Pre and post-tests included measures of freezing, balance, motor severity, quality-of-life and gait speed. RESULTS: No falls or injuries occurred and attendance was high. Participants had favorable feedback and showed reduced freezing and improvements in balance and gait. CONCLUSION: Preliminary data suggest the FOG boot camp was feasible, safe and effective.

Modeling, Detecting, and Tracking Freezing of Gait in Parkinson Disease Using Inertial Sensors.

In this paper, we develop new methods to automatically detect the onset and duration of freezing of gait (FOG) in people with Parkinson disease (PD) in real time, using inertial sensors. We first build a physical model that describes the trembling motion during the FOG events. Then, we design a generalized likelihood ratio test framework to develop a two-stage detector for determining the zero-velocity and trembling events during gait. Thereafter, to filter out falsely detected FOG events, we develop a point-process filter that combines the output of the detectors with information about the speed of the foot, provided by a foot-mounted inertial navigation system. We computed the probability of FOG by using the point-process filter to determine the onset and duration of the FOG event. Finally, we validate the performance of the proposed system design using real data obtained from people with PD who performed a set of gait tasks. We compare our FOG detection results with an existing method that only uses accelerometer data. The results indicate that our method yields 81.03% accuracy in detecting FOG events and a threefold decrease in the false-alarm rate relative to the existing method.

Effects of exercise on gait and motor imagery in people with Parkinson disease and freezing of gait.

INTRODUCTION: Exercise improves gait in Parkinson disease (PD), but whether exercise differentially affects people with PD with (freezers) and without freezing of gait (non-freezers) remains unclear. This study examines exercise's effects on gait performance, neural correlates related to these effects, and potential neural activation differences between freezers and non-freezers during motor imagery (MI) of gait. METHODS: Thirty-seven participants from a larger exercise intervention completed behavioral assessments and functional magnetic resonance imaging (fMRI) scans before and after a 12-week exercise intervention. Gait performance was characterized using gait velocity and stride length, and a region of interest (ROI) fMRI analysis examined task-based blood oxygen-level dependent (BOLD) signal changes of the somatomotor network (SMN) during MI of forward (IMG-FWD) and backward (IMG-BWD) gait. RESULTS: Velocity (F(1,34) = 55.04, p < 0.001) and stride length (F(1,34) = 77.58, p < 0.001) were significantly lower for backward versus forward walking in all participants. The ROI analysis showed freezers had lower BOLD signal compared to non-freezers in the cerebellum (F(1,32) = 7.01, p = 0.01), primary motor (left: F(1,32) = 7.09, p = 0.01; right: F(1,32) = 7.45, p = 0.01), and primary sensory (left: F(1,32) = 9.59, p = 0.004; right: F(1,32) = 8.18, p = 0.007) cortices during IMG-BWD only. The evidence suggests the exercise intervention did not affect gait or BOLD signal during MI. CONCLUSION: While all participants had significantly slower and shorter backward velocity and stride length, respectively, the exercise intervention had no effect. Similarly, BOLD signal during MI did not change with exercise; however, freezers had significantly lower BOLD signal during IMG-BWD compared to non-freezers. This suggests potential decreased recruitment of the SMN during MI of gait in freezers.

Physical therapy and deep brain stimulation in Parkinson's Disease: protocol for a pilot randomized controlled trial.

BACKGROUND: Subthalamic nucleus deep brain stimulation (STN-DBS) reduces tremor, muscle stiffness, and bradykinesia in people with Parkinson's Disease (PD). Walking speed, known to be reduced in PD, typically improves after surgery; however, other important aspects of gait may not improve. Furthermore, balance may worsen and falls may increase after STN-DBS. Thus, interventions to improve balance and gait could reduce morbidity and improve quality of life following STN-DBS. Physical therapy (PT) effectively improves balance and gait in people with PD, but studies on the effects of PT have not been extended to those treated with STN-DBS. As such, the efficacy, safety, and feasibility of PT in this population remain to be determined. The purpose of this pilot study is to address these unmet needs. We hypothesize that PT designed to target balance and gait impairment will be effective, safe, and feasible in this population. METHODS/DESIGN: Participants with PD treated with STN-DBS will be randomly assigned to either a PT or control group. Participants assigned to PT will complete an 8-week, twice-weekly PT program consisting of exercises designed to improve balance and gait. Control group participants will receive the current standard of care following STN-DBS, which does not include prescription of PT. The primary aim is to assess preliminary efficacy of PT on balance (Balance Evaluation Systems Test). A secondary aim is to assess efficacy of PT on gait (GAITRite instrumented walkway). Participants will be assessed OFF medication/OFF stimulation and ON medication/ON stimulation at baseline and at 8 and 12 weeks after baseline. Adverse events will be measured over the duration of the study, and adherence to PT will be measured to determine feasibility. DISCUSSION: To our knowledge, this will be the first study to explore the preliminary efficacy, safety, and feasibility of PT for individuals with PD with STN-DBS. If the study suggests potential efficacy, then this would justify larger trials to test effectiveness and safety of PT for those with PD with STN-DBS. TRIAL REGISTRATION: NCT03181282 (clinicaltrials.gov). Registered on 7 June 2017.

Maximum Step Length Test Performance in People With Parkinson Disease: A Cross-sectional Study.

BACKGROUND AND PURPOSE: The Maximum Step Length Test (MSLT), a measure of one's capacity to produce a large step, has been studied in older adults, but not in people with Parkinson disease (PD). We characterized performance and construct validity of the MSLT in PD. METHODS: Forty participants (mean age: 65.12 ± 8.20 years; 45% female) with idiopathic PD completed the MSLT while "OFF" and "ON" anti-PD medication. Construct validity was investigated by examining relationships between MSLT and measures of motor performance. The following measures were collected: Mini-Balance Evaluation Systems Test (Mini-BESTest), Activities-specific Balance Confidence (ABC) scale, gait velocity, 6-minute walk test (6MWT), Movement Disorder Society-Unified Parkinson Disease Rating Scale subsection III (MDS-UPDRS III), and Timed Up and Go (TUG) test. A repeated-measures analysis of variance tested for main effects of medication and stepping direction and the interaction between the 2. Pearson or Spearman correlations were used to assess the relationships between MSLT and motor performance measures (α = 0.05). RESULTS: Regardless of medication status, participants stepped further in the forward direction compared with the backward and lateral directions (P < 0.001). Participants increased MSLT performance when ON-medication compared with OFF-medication (P = 0.004). Regardless of medication status, MSLT was moderately to strongly related to Mini-BESTest, TUG, and 6MWT. DISCUSSION AND CONCLUSIONS: People with PD stepped furthest in the forward direction when performing the MSLT. Increased MSLT performance was observed in the ON-medication state compared with OFF-medication; however, the small increase may not be clinically meaningful. Given the relationships between the MSLT and the Mini-BESTest, 6MWT, and TUG, MSLT performance appears to be associated with balance and gait hypokinesia in people with PD.Video Abstract available for more insights from the authors (see Video, Supplemental Digital Content 1, http://links.lww.com/JNPT/A186).