Good agreement between smart device and inertial sensor-based gait parameters during a 6-min walk.

BACKGROUND: Traditional laboratory-based kinetic and kinematic gait analyses are expensive, time-intensive, and impractical for clinical settings. Inertial sensors have gained popularity in gait analysis research and more recently smart devices have been employed to provide quantification of gait. However, no study to date has investigated the agreement between smart device and inertial sensor-based gait parameters during prolonged walking. RESEARCH QUESTION: Compare spatiotemporal gait metrics measured with a smart device versus previously validated inertial sensors. METHODS: Twenty neurologically healthy young adults (7 women; age: 25.0 ±â€¯3.7 years; BMI: 23.4 ±â€¯2.9 kg/m2) performed a 6-min walk test (6MWT) wearing inertial sensors and smart devices to record stride duration, stride length, cadence, and gait speed. Pearson correlations were used to assess associations between spatiotemporal measures from the two devices and agreement between the two methods was assessed with Bland-Altman plots and limits of agreement. RESULTS: All spatiotemporal gait metrics (stride duration, cadence, stride length and gait speed) showed strong (r>0.9) associations and good agreement between the two devices. SIGNIFICANCE: Smart devices are capable of accurately reflecting many of the spatiotemporal gait metrics of inertial sensors. As the smart devices also accurately reflected individual leg output, future studies may apply this analytical strategy to clinical populations, to identify hallmarks of disability status and disease progression in a more ecologically valid environment.

Glucose uptake of the spinal cord in patients with multiple sclerosis detected by ¹8F-fluorodeoxyglucose PET/CT after walking.

STUDY DESIGN: Case report. OBJECTIVES: To determine [(18)F]-fluorodeoxyglucose ([(18)F]-FDG) uptake in the spinal cord of patients with multiple sclerosis (MS) was compared with healthy controls after treadmill walking. SETTING: Colorado Translational Research Imaging Center, University of Colorado School of Medicine, Aurora, CO, USA. METHODS: Eight mildly disabled patients with MS and eight healthy subjects performed 15 min of treadmill walking at a self-selected pace. Two minutes after walking began, each participant was injected with ≈8 mCi of [(18)F]-FDG into a catheter inserted into an antecubital vein. Immediately after walking positron emission tomography/computed tomography (PET/CT) imaging was performed on each participant. Images were analyzed to determine [(18)F]-FDG uptake within the spinal cord. RESULTS: Total spinal cord [(18)F]-FDG uptake was lower in patients with MS (1.48±0.36 and 1.55±0.33, P=0.04), specifically within the thoracic (1.32±0.27 and 1.41±0.24, P<0.01) and the lumbar (1.58±0.40 and 1.89±0.43, P=0.04) spinal cord regions. CONCLUSION: This is the first report of [(18)F]-FDG uptake in the spinal cord of patients with MS. The decreased [(18)F]-FDG uptake within the thoracic and lumbar spinal cord regions could be associated with autonomic nervous system and walking/motor dysfunctions that are often seen in patients with MS. PET/CT imaging with [(18)F]-FDG is highly useful for the demonstration of impaired glucose metabolism in the spinal cord of patients with MS.

Asymmetric glucose uptake in leg muscles of patients with Multiple Sclerosis during walking detected by [18F]-FDG PET/CT.

BACKGROUND: In patients with Multiple Sclerosis (MS), comparative leg muscle strength asymmetries are common and typically accompanied by walking difficulties. Underlying mechanisms for these asymmetries are not completely known, but altered muscle energetics may play a role. OBJECTIVE: To investigate glucose uptake asymmetries in leg muscles of patients with mild MS during walking. METHODS: Eight MS and 8 healthy control (CON) participants performed a 15-min treadmill walking test at self-selected speed. They were injected with a glucose tracer (18F-FDG) two minutes into the test and immediately upon completion, underwent Positron Emission Tomography/Computed Tomography (PET/CT) imaging. RESULTS: MS group walked at a lower speed than the healthy control group (P < 0.01), however it was found that: 1) ([18F]-FDG) uptake in knee and hip flexors was higher compared to the CON group (P = 0.02); 2) the MS group exhibited asymmetrical strength of the knee flexors (P = 0.03); 3) [18F]-FDG uptake was significantly lower in the weaker knee flexors of patients with MS (P < 0.01). CONCLUSIONS: [18F]-FDG uptake and strength asymmetries in the legs of patients with MS indicate greater metabolic costs during activity, which may play a major role in premature muscle fatigability and subsequent impaired walking capacity.

Influence of rest duration on muscle activation during submaximal intermittent contractions with the elbow flexor muscles.

AIM: The purpose of the study was to compare the influence of two intervals between consecutive intermittent contractions with the elbow flexors on time to failure and the accompanying changes in electromyographic (EMG) activity and excitation-contraction coupling. METHODS: Subjects performed 6-s intermittent isometric contractions at 50% of the maximal voluntary contraction (MVC) force to task failure in two sessions. The recovery period between consecutive contractions was 4-s (short recovery protocol, SRP) in one and 14-s (long recovery protocol, LRP) in the other session. RESULTS: The number of contractions performed to task failure was greater for the LRP (99 + or - 24) compared with the SRP (46 + or - 18; P<0.05). The amplitude and duration of the maximal compound action potential (M-wave) did not change during either protocol. EMG activity (% peak MVC) for the elbow flexors and the force fluctuations increased more rapidly during the SRP compared with the LRP (P<0.05) and was greater at task failure for the SRP protocol (P<0.05). These changes were accompanied by a faster decline in twitch force. CONCLUSIONS: The results indicate that a briefer interval between consecutive contractions was associated with a more rapid impairment of the excitation-contraction coupling and a faster increase in muscle activation, despite a similar net muscle force for the two protocols.