A Kinematic Comparison of Spring-Loaded and Traditional Crutches

2011 ◽  
Vol 20 (2) ◽  
pp. 198-206 ◽  
Author(s):  
Matthew K. Seeley ◽  
Iain Hunter ◽  
Thomas Bateman ◽  
Adam Roggia ◽  
Brad J. Larson ◽  
...  
Keyword(s):  
Potential Energy ◽  
Outcome Measures ◽  
High Speed ◽  
Elastic Potential ◽  
Ground Contact ◽  
Type Design ◽  
Additional Peak ◽  
Dependent Variables ◽  
Elastic Potential Energy ◽  
Independent Variable

Context:A novel spring-loaded-crutch design may provide patients additional forward velocity, relative to traditional axillary crutches; however, this idea has not yet been evaluated.Objective:To quantify elastic potential energy stored by spring-loaded crutches during crutch–ground contact and determine whether this energy increases forward velocity for patients during crutch ambulation. Because elastic potential energy is likely stored by the spring-loaded crutch during ambulation, the authors hypothesized that subjects would exhibit greater peak instantaneous forward velocity during crutch–ground contact and increased preferred ambulation speed during spring-loaded-crutch ambulation, relative to traditional-crutch ambulation.Design:Within-subject.Setting:Biomechanics laboratory.Participants:10 healthy men and 10 healthy women.Interventions:The independent variable was crutch type: Subjects used spring-loaded and traditional axillary crutches to ambulate at standardized and preferred speeds.Main Outcome Measures:The primary dependent variables were peak instantaneous forward velocity and preferred ambulation speed; these variables were quantified using high-speed videography and an optoelectronic timing device, respectively. Between-crutches differences for the dependent variables were evaluated using paired t tests (α = .05). Elastic potential energy stored by the spring-loaded crutches during crutch–ground contact was also quantified via videography.Results:Peak forward velocity during crutch–ground contact was 5% greater (P < .001) for spring-loaded-crutch ambulation than for traditional-crutch ambulation. Preferred ambulation speed, however, did not significantly differ (P = .538) between crutch types. The spring-loaded crutches stored an average of 2.50 ± 1.96 J of elastic potential energy during crutch–ground contact.Conclusions:The spring-loaded crutches appear to have provided subjects with additional peak instantaneous forward velocity. This increased velocity, however, was relatively small and did not increase preferred ambulation speed.

scholarly journals Assessment of Subacromial Space and Its Relationship With Scapular Upward Rotation in College Baseball Players

2013 ◽  
Vol 22 (3) ◽  
pp. 216-223 ◽  
Author(s):  
Stephen John Thomas ◽  
Charles Buz Swanik ◽  
Thomas W. Kaminski ◽  
Jill S. Higginson ◽  
Kathleen A. Swanik ◽  
...  
Keyword(s):  
Outcome Measures ◽  
Laboratory Setting ◽  
Subacromial Space ◽  
Baseball Players ◽  
Type Design ◽  
Dependent Variables ◽  
Injured Population ◽  
College Baseball ◽  
Acromiohumeral Distance ◽  
The Relationship

Context:Subacromial impingement is a common injury in baseball players and has been linked to a reduction in the subacromial space. In addition, it has been suggested that decreases in scapular upward rotation will lead to decreases in the subacromial space and ultimately impingement syndrome.Objective:The objective of this study was to evaluate the relationship between acromiohumeral distance and scapular upward rotation in healthy college baseball players.Design:Posttest-only study design.Setting:Controlled laboratory setting.Participants:24 healthy college baseball players.Intervention:Participants were measured for all dependent variables at preseason.Main Outcome Measures:Acromiohumeral distance at rest and 90° of abduction was measured with a diagnostic ultrasound unit. Scapular upward rotation at rest and 90° of abduction was measured with a digital inclinometer.Results:Dominant-arm acromiohumeral distance at rest and 90° of abduction (P = .694, P = .840) was not significantly different than in the nondominant arm. In addition, there was not a significant correlation between acromiohumeral distance and scapular upward rotation at rest and 90° of abduction for either the dominant or the nondominant arm.Conclusions:These results indicate that the acromiohumeral distance is not adapting in the dominant arm in healthy throwing athletes. In addition, a relationship was not identified between acromiohumeral distance and scapular upward rotation, which was previously suggested. These results may suggest that changes that are typically seen in an injured population may be occurring due to the injury and are not preexisting. In addition, scapular upward rotation may not be the only contributing factor to acromiohumeral distance.

An Accurate and Robust Geometrically Exact Curved Beam Formulation for Multibody Dynamic Analysis

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
H. Ren ◽  
W. Fan ◽  
W. D. Zhu
Keyword(s):  
Potential Energy ◽  
Cross Section ◽  
Small Strain ◽  
Elastic Potential ◽  
Rotation Vector ◽  
Benchmark Problems ◽  
Position Vector ◽  
Current Formulation ◽  
Geometrically Exact Beam ◽  
Elastic Potential Energy

An accurate and robust geometrically exact beam formulation (GEBF) is developed to simulate the dynamics of a beam with large deformations and large rotations. The undeformed configuration of the centroid line of the beam can be either straight or curved, and cross sections of the beam can be either uniform or nonuniform with arbitrary shapes. The beam is described by the position of the centroid line and a local frame of a cross section, and a rotation vector is used to characterize the rotation of the cross section. The elastic potential energy of the beam is derived using continuum mechanics with the small-strain assumption and linear constitutive relation, and a factor naturally arises in the elastic potential energy, which can resolve a drawback of the traditional GEBF. Shape functions of the position vector and rotation vector are carefully chosen, and numerical incompatibility due to independent discretization of the position vector and rotation vector is resolved, which can avoid the shear locking problem. Numerical singularity of the rotation vector with its norm equal to zero is eliminated by Taylor polynomials. A rescaling strategy is adopted to resolve the singularity problem with its norm equal to 2mπ, where m is a nonzero integer. The current formulation can be used to handle linear and nonlinear dynamics of beams under arbitrary concentrated and distributed loads. Several benchmark problems are simulated using the current formulation to validate its accuracy, adaptiveness, and robustness.

A Slinky’s Elastic Potential Energy

2020 ◽  
Vol 58 (3) ◽  
pp. 198-199
Author(s):  
Philip Gash
Keyword(s):  
Potential Energy ◽  
Elastic Potential ◽  
Elastic Potential Energy

A Model for Quantifying System Evolvability Based on Excess and Capacity

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
Morgan W. P. Tackett ◽  
Christopher A. Mattson ◽  
Scott M. Ferguson
Keyword(s):  
Potential Energy ◽  
Design Process ◽  
Elastic Potential ◽  
Aircraft Carrier ◽  
Elastic Potential Energy ◽  
Engineered Systems ◽  
Mathematical Relationships ◽  
Service Building

An important factor in system longevity is service-phase evolvability, which is defined as the ability of a system to physically transform from one configuration to a more desirable configuration while in service. These transformations may or may not be known during the design process, and may or may not be reversible. In a different study, we examined 210 engineered systems and found that system excess and modularity allow a system to evolve while in service. Building on this observation, the present paper introduces mathematical relationships that map a system's excess to that system's ability to evolve. As introduced in this paper, this relationship is derived from elastic potential-energy theories. The use of the evolvability measure, and other related measures presented herein, are illustrated with simple examples and applied to the design of U.S. Navy nuclear aircraft carriers. Using these relationships, we show that the Navy's new Ford-class aircraft carrier is measurably more evolvable than the Nimitz-class carriers. While the ability for systems to evolve is based on excess and modularity, this paper is focused only on excess. The mapping between modularity and evolvability is the focus of another work by the authors.

Change in Glenohumeral Rotation and Scapular Position After a Division I Collegiate Baseball Season

2013 ◽  
Vol 22 (2) ◽  
pp. 115-121 ◽  
Author(s):  
Stephen John Thomas ◽  
Charles B. Swanik ◽  
Kathleen Swanik ◽  
John D. Kelly
Keyword(s):  
Outcome Measures ◽  
External Rotation ◽  
Division I ◽  
Laboratory Setting ◽  
Anterior Instability ◽  
Baseball Players ◽  
Elbow Injury ◽  
Type Design ◽  
Dependent Variables ◽  
Collegiate Baseball

Context:Pathologies such as anterior instability and impingement are common in baseball and have been linked to decreases in internal-rotation (IR) motion and concurrent increases in external-rotation (ER) motion. In addition, alterations to scapular upward rotation have been identified in this population.Objective:To measure glenohumeral (GH) IR and ER rotation, total range of motion (ROM), and scapular upward rotation throughout the course of a Division I collegiate baseball season.Design:Pretest to posttest study.Setting:Controlled laboratory setting.Participants:Thirty-one collegiate baseball players with no current shoulder or elbow injury completed this study.Intervention:Participants were measured for all dependent variables at preseason and postseason.Main Outcome Measures:GH IR and ER were measured supine with the scapula stabilized. Total GH ROM was calculated as the sum of IR and ER measures. Scapular upward rotation was tested at rest, 60°, 90°, and 120° of GH abduction in the scapular plane.Results:Overall, the dominant arm had significantly less GH IR and significantly more ER than the nondominant arm. The total motion on the dominant arm was significantly less than on the nondominant arm. No significant differences were observed from preseason to postseason for IR, ER, or total motion. Dominant-arm scapular upward rotation significantly decreased at 60°, 90°, and 120° of abduction from preseason to postseason.Conclusion:Collegiate baseball players presented with significant GH-motion differences (decreases in IR and increases in ER) in their dominant arm compared with their nondominant arm. There was also significantly less total motion on the dominant arm. After 12 wk of competitive Division I collegiate baseball, there were significant decreases in upward rotation over the season.

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