The Microsoft HoloLens 2 Provides Accurate Biomechanical Measures of Performance During Military-Relevant Activities in Healthy Adults.

INTRODUCTION: Augmented reality systems, like the HoloLens 2 (HL2), have the potential to provide accurate assessments of mild traumatic brain injury (mTBI) symptoms in military personnel by simulating complex military scenarios while objectively measuring the user's movements with embedded motion sensors. The aim of this project was to determine if biomechanical measures of marching and squatting, derived from the HL2 motion sensors, were statistically equivalent, within 5%, to metrics derived from the gold-standard three-dimensional motion capture (MoCap) system. MATERIALS AND METHODS: Sixty-four adults (18-45 years; 34 males) completed a squatting and a marching task under single- (motor) and dual-task (motor + cognitive) conditions. Positional data from the HL2 and MoCap were simultaneously collected during the tasks and used to calculate and compare biomechanical outcomes. The HL2's augmented reality capabilities were utilized to deliver the cognitive component of the marching dual task. RESULTS: Equivalence testing indicated the HL2 and MoCap measures were within 5% in all squatting metrics-trial time, squat duration, squat velocity, squat depth, and dwell time. Marching metrics, including trial time, step count, stepping rate, and step interval, were also equivalent between the two systems. The mean reaction time for responses during the Stroop test was 810 (125) milliseconds per response. CONCLUSIONS: Biomechanical outcomes characterizing performance during two common military movements, squatting and marching, were equivalent between the HL2 and MoCap systems in healthy adults. Squatting and marching are two military-relevant tasks that require strength, motor coordination, and balance to perform, all of which are known to be affected by mTBI. Taken together, the data provide support for using the HL2 platform to deliver military-specific assessment scenarios and accurately measure performance during these activities. Utilizing objective and quantitative measures of motor function may enhance the management of military mTBI and reduce unnecessary risk to service members.

The Microsoft HoloLens 2 Provides Accurate Measures of Gait, Turning, and Functional Mobility in Healthy Adults.

Augmented-reality (AR) headsets, such as the Microsoft HoloLens 2 (HL2), have the potential to be the next generation of wearable technology as they provide interactive digital stimuli in the context of ecologically-valid daily activities while containing inertial measurement units (IMUs) to objectively quantify the movements of the user. A necessary precursor to the widespread utilization of the HL2 in the fields of movement science and rehabilitation is the rigorous validation of its capacity to generate biomechanical outcomes comparable to gold standard outcomes. This project sought to determine equivalency of kinematic outcomes characterizing lower-extremity function derived from the HL2 and three-dimensional (3D) motion capture systems (MoCap). Sixty-six healthy adults completed two lower-extremity tasks while kinematic data were collected from the HL2 and MoCap: (1) continuous walking and (2) timed up-and-go (TUG). For all the continuous walking metrics (cumulative distance, time, number of steps, step and stride length, and velocity), equivalence testing indicated that the HL2 and MoCap were statistically equivalent (error ≤ 5%). The TUG metrics, including turn duration and turn velocity, were also statistically equivalent between the two systems. The accurate quantification of gait and turning using a wearable such as the HL2 provides initial evidence for its use as a platform for the development and delivery of gait and mobility assessments, including the in-person and remote delivery of highly salient digital movement assessments and rehabilitation protocols.

Parkinson's gait kinematics deteriorates across multiple cognitive domains under dual-task paradigms.

OBJECTIVE: The symptoms of Parkinson's disease (PD) in many circumstances lead to gait dysfunction which contribute to decreased mobility, reduced quality of life, and increased risk of falling. Dual-task conditions have been shown to amplify gait dysfunction from a spatiotemporal parameter standpoint; however, less is known regarding gait joint kinematics under dual-task conditions in PD, specifically across multiple cognitive domains. The purpose of this project was to systematically characterize lower extremity joint kinematics in individuals with mild-moderate PD under dual-task paradigms across multiple cognitive domains. PATIENTS AND METHODS: Twenty-three individuals with idiopathic Parkinson's disease participated in this observational study evaluating hip, knee, and ankle joint kinematics while walking on a self-paced treadmill under dual-task conditions that taxed memory, attention, verbal fluency, and information processing. RESULTS: Gait velocity and range of motion at the ankle, knee, and hip decreased (p < 0.05) under all of the dual-task conditions. Hip kinematics were affected to a greater extent than the ankle and knee, with reduction in flexion and extension during all timestamps of the gait cycle (p < 0.05) under all dual-task conditions. CONCLUSION: The worsening of gait kinematics under dual-task conditions regardless of the aspect of cognition being challenged suggest that information processing and motor output are unable to withstand dual-task loads without consequence. These study results provide insight for target areas to focus on during therapeutic interventions in order to help minimize gait kinematic decrements observed under dual-task conditions.

Improvements in temporal and postural aspects of gait vary following single- and multi-modal training in individuals with Parkinson's disease.

INTRODUCTION: Gait deteriorates under dual task conditions in individuals with Parkinson's disease (PD). Therapeutic interventions have the potential to improve dual task performance, although it remains unclear how training affects gait performance under varying cognitive domains. The primary aim of this trial was to determine the effect of an 8-week single- or multi-modal gait and cognitive training intervention on dual task performance across cognitive domains in individuals with PD. METHODS: Twenty individuals with PD completed a 24-session single-modal training (SMT, n = 10) or multi-modal training (MMT, n = 10). The SMT group performed gait and cognitive training sequentially; the MMT group performed gait and cognitive training simultaneously. Gait was analyzed using motion capture analysis during simultaneous performance of six untrained cognitive tasks. RESULTS: Both SMT and MMT resulted in significant improvements in MDS-UPDRS III scores and gait performance. Improvements in arm swing were more prevalent in the less affected extremity, while improvements in the more affected upper extremity favored the MMT group. Temporal aspects of gait (velocity, step length) improved under all dual task conditions, while postural aspects of gait (step width, arm swing) varied by cognitive task. CONCLUSIONS: Both SMT and MMT were effective in improving motor and dual task performance in PD. Improvements in upper extremity gait variables in the MMT group may indicate that the complexity of the training is be beneficial in PD. The different responses in temporal and postural aspects of gait highlights the need for clinicians to train multiple cognitive domains during behavioral therapy.

The Two Minute Walk Test Overground and on a Self-Paced Treadmill Detects Dual Task Deficits in Individuals With Parkinson's Disease.

The aim of this project was to 1) evaluate the potential of the Two Minute Walk Test (2MWT) to detect declines in gait velocity under dual task conditions, and 2) compare gait velocity overground and on a self-paced treadmill in Parkinson's disease (PD). Twenty-three individuals with PD completed the 2MWT under single and dual task (serial 7s) conditions overground and on a self-paced treadmill. There was a significant decrease in gait velocity from single to dual task conditions overground (1.32±.22 m/sec to 1.10±.25 m/sec, p <.001) and on the self-paced treadmill (1.24±.21 m/sec to 1.05±.25 m/sec, p <.001). Overground and treadmill velocities were not statistically different from each other; however, differences approached or exceeded the minimal clinical important difference. The 2MWT coupled with a cognitive task provides an effective model of identifying dual task declines in individuals with PD. Further studies comparing overground and self-paced treadmill velocity is warranted in PD.

Dual-task Interference Disrupts Parkinson's Gait Across Multiple Cognitive Domains.

Gait dysfunction, a hallmark of Parkinson's disease, contributes to a relatively high incidence of falling. Gait function is further diminished during the performance of a motor-cognitive task (i.e., dual-task). It is unclear if Parkinson's disease-related dual-task deficits are related to a specific area of cognitive function or are the result of a more global decline in executive function. The aim of this project was to systematically evaluate gait performance to determine if gait dysfunction is restricted to certain types of executive function or a global phenomenon in individuals with Parkinson's disease. Twenty-three individuals with mild-moderate Parkinson's disease completed a series of dual-task conditions in which gait was paired with cognitive tasks requiring: working memory (0, 1, and 2-back), attention and problem solving (serial-7 subtraction), verbal memory (digit recall), semantic memory (Controlled Oral Word Association) and information processing speed (visual Stroop test). The results demonstrate that individuals with mild-moderate Parkinson's disease have a generalized worsening of spatial-temporal gait parameters regardless of the specific cognitive demand being performed concurrently. Overall, gait velocity decreased (p < 0.01) and stride and stance time both increased (p < 0.01) across all cognitive conditions. The attention and problem solving task resulted in the greatest number of gait parameter decrements. Results indicated that performance on cognitive tasks remained unchanged from single-task to dual-task conditions. Diminished gait performance under dual-task conditions across different cognitive function domains suggests a global Parkinson's disease-related deficit in information processing and regulation of gait.

Altered kinematics of arm swing in Parkinson's disease patients indicates declines in gait under dual-task conditions.

OBJECTIVE: Declines in simultaneous performance of a cognitive and motor task are present in Parkinson's disease due to compromised basal ganglia function related to information processing. The aim of this project was to determine if biomechanical measures of arm swing could be used as a marker of gait function under dual-task conditions in Parkinson's disease patients. METHODS: Twenty-three patients with Parkinson's disease completed single and dual-task cognitive-motor tests while walking on a treadmill at a self-selected rate. Multiple cognitive domains were evaluated with five cognitive tests. Cognitive tests were completed in isolation (single-task) and simultaneously with gait (dual-task). Upper extremity biomechanical data were gathered using the Motek CAREN system. Primary outcomes characterizing arm swing were: path length, normalized jerk, coefficient of variation of arm swing time, and cognitive performance. RESULTS: Performance on the cognitive tasks were similar across single and dual-task conditions. However, biomechanical measures exhibited significant changes between single and dual-task conditions, with the greatest changes occurring in the most challenging conditions. Arm swing path length decreased significantly from single to dual-task, with the greatest decrease of 21.16%. Jerk, characterizing smoothness, increased significantly when moving from single to dual-task conditions. CONCLUSION: The simultaneous performance of a cognitive and gait task resulted in decrements in arm swing while cognitive performance was maintained. Arm swing outcomes provide a sensitive measure of declines in gait function in Parkinson's disease under dual-task conditions. The quantification of arm swing is a feasible approach to identifying and evaluating gait related declines under dual-task conditions.

Simulation of lower limb axial arterial length change during locomotion.

The effect of external forces on axial arterial wall mechanics has conventionally been regarded as secondary to hemodynamic influences. However, arteries are similar to muscles in terms of the manner in which they traverse joints, and their three-dimensional geometrical requirements for joint motion. This study considers axial arterial shortening and elongation due to motion of the lower extremity during gait, ascending stairs, and sitting-to-standing motion. Arterial length change was simulated by means of a graphics based anatomic and kinematic model of the lower extremity. This model estimated the axial shortening to be as much as 23% for the femoropopliteal arterial region and as much as 21% for the iliac artery. A strong correlation was observed between femoropopliteal artery shortening and maximum knee flexion angle (r²=0.8) as well as iliac artery shortening and maximum hip angle flexion (r²=0.9). This implies a significant mechanical influence of locomotion on arterial behavior in addition to hemodynamics factors. Vascular tissue has high demands for axial compliance that should be considered in the pathology of atherosclerosis and the design of vascular implants.