Publications by authors named "James B Tracy"

For some individuals with severe socket-related problems, prosthesis osseointegration directly connects a prosthesis to the residual limb creating a bone-anchored limb (BAL). We compared dynamic gait stability and between-limb stability symmetry, as measured by the Margin of Stability (MoS) and the Normalized Symmetry Index (NSI), for people with unilateral transfemoral amputation before and one-year after BAL implantation. The MoS provides a mechanical construct to assess dynamic gait stability and infer center of mass and limb control by relating the center of mass and velocity to the base of support.

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Background: A bone-anchored limb (BAL) is an alternative to a traditional socket-type prosthesis for people with transfemoral amputation. Early laboratory-based evidence suggests improvement in joint and limb loading mechanics during walking with a BAL compared to socket prosthesis use. However, changes in cumulative joint and limb loading measures, which may be predictive of degenerative joint disease progression, remain unknown.

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Article Synopsis
  • The study investigates how body size affects different expressions of stability margins in walking, specifically looking at impulses and changes in velocity related to center of mass.
  • The results showed strong correlations between impulse-based stability margins and body size, with significant differences between groups, while other expressions had weak correlations and differences.
  • The researchers recommend using impulse expressions for stability margins and suggest a scaled, unitless impulse when scaling is necessary.
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The Margin of Stability (MOS) is often assessed relative to the intended, linear path of walking progression. When an unanticipated or irregular change in direction occurs, such as during a sudden turn or during activities of daily living, distinguishing the lateral from anteroposterior MOS can be challenging. The purpose of this study was to assess an anatomically orientated method of calculating the MOS using the pelvic orientation to define lateral and anteroposterior directions.

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Background: Understanding individual limb contributions to standing postural control is valuable when evaluating populations with asymmetric function (e.g., stroke, amputations).

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Background: Standing postural sway is often quantified from center of pressure trajectories. During assessments of longer durations, children may fidget, thus limiting the feasibility and validity of sway recordings.

Research Question: Do postural sway sample durations less than 30 s maintain construct and concurrent validity?

Methods: In this case-control, observational study, we measured postural sway in 41 children (age 5-12 years, 23 typically developing (TD); 18 with spastic cerebral palsy (CP), 13 diplegic and 5 hemiplegic, 11 GMFCS level I and 7 level II) for 30-second eyes-opened and eyes-closed conditions.

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Running is a common exercise with numerous health benefits. Vertical ground reaction force (vGRF) influences running injury risk and running performance. Measurement of vGRF during running is now primarily constrained to a laboratory setting.

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Cerebral palsy is a neurodevelopmental movement disorder that affects coordination and balance. Therapeutic treatments for balance deficiencies in this population primarily focus on the musculoskeletal system, whereas the neural basis of balance impairment is often overlooked. Magnetic resonance elastography (MRE) is an emerging technique that has the ability to sensitively assess microstructural brain health through measurements of neural tissue stiffness.

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Aim: To compare anterior and posterior standing balance reactions, as measured by single-stepping thresholds, in children with and without spastic cerebral palsy (CP).

Method: Seventeen ambulatory children with spastic CP (eight males, nine females) and 28 typically developing children (13 males, 15 females; age range 5-12y, mean [SD] 9y 2mo [2y 3mo]), were included in this cross-sectional, observational study. Balance reaction skill was quantified as anterior and posterior single-stepping thresholds, or the treadmill-induced perturbations that consistently elicited a step in that direction.

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Background: Static balance performance is a common metric for evaluating the development of postural control in children. Less is known about the potentially independent development of dynamic balance performance.

Research Question: How does age relate to static (i.

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Background: Cerebral palsy (CP) is associated with a high risk of falling during walking. Many gait abnormalities associated with CP likely alter foot placement and center of mass (CoM) movement in a way that affects anterior or lateral dynamic stability, in turn influencing fall risk.

Research Question: Do children with CP demonstrate altered anterior or lateral dynamic stability compared to typically-developing (TD) children?

Methods: In this case-control, observational study, we measured gait kinematics of two groups of children (15 CP, 11 GMFCS level I, 4 GMFCS level II; 14 TD; age 5-12) in walking conditions of a preferred speed, a fast speed, and a preferred speed while completing a cognitive task.

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This paper describes a method for the estimation of the 3D ground reaction force (GRF) during human walking using novel nanocomposite piezo-responsive foam (NCPF) sensors. Nine subjects (5 male, 4 female) walked on a force-instrumented treadmill at 1.34 m/s for 120 s each while wearing a shoe that was instrumented with four NCPF sensors.

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