Contractile Filament Stress: Comparison of Different Disease States in Man

Author Institution: Department of Engineering and Department of Physiology, Wright State UniversityCardiac catheterization data on 39 patients was classified in 5 cardiovascular groups: normal, compensated volume overload, decompensated volume overload, compensated pressure overload, and congestive cardiomyopathy. Both the Lagrangian stress and contractile filament stress for the circumferential axis and the longitudinal axis were computed over a complete cardiac cycle. Contractile filament stress was 24% higher than Lagrangian stress in the circumferential direction, and 43% higher than Lagrangian stress in the longitudinal direction. The percent difference in stress between the contractile filament stress and Lagrangian stress was greatest for patients with pressure overload, and least for patients with compensated volume overload. No significant difference in calculated wall stress was noted between the normal group and the 4 pathological groups. Circumferential velocity of the contractile element occurring at peak stress was plotted as a function of peak contractile filament stress and patients with compensated pressure overload exhibited high values of both velocity and peak stress. Patients with congestive cardiomyopathy showed low values of both velocity and peak stress. Circumferential velocity of the contractile element occurring throughout the cardiac cycle was plotted as a function of both the instantaneous Lagrangian stress and the instantaneous contractile filament stress, resulting in 2 stress-velocity curves for each patient. The value of the maximum velocity extrapolated from either stress-velocity curve was approximately the same, but the maximum stress extrapolated from the contractile filament stress-velocity curve was significantly higher than the maximum stress extrapolated from the Lagrangian stressvelocity curve. The product of peak contractile filament stress in the circumferential direction times heart rate was a clinically useful index of myocardial oxygen consumption, and predicted a lower rate of oxygen consumption than did the product of peak developed stress times heart rate

A review of recent perspectives on biomechanical risk factors associated with anterior cruciate ligament injury

There is considerable evidence to support a number of biomechanical risk factors associated with non-contact anterior cruciate ligament (ACL) injury. This paper aimed to review these biomechanical risk factors and highlight future directions relating to them. Current perspectives investigating trunk position and relationships between strength, muscle activity and biomechanics during landing/cutting highlight the importance of increasing hamstring muscle force during dynamic movements through altering strength, muscle activity, muscle length and contraction velocity. In particular, increased trunk flexion during landing/cutting and greater hamstring strength are likely to increase hamstring muscle force during landing and cutting which have been associated with reduced ACL injury risk. Decision making has also been shown to influence landing biomechanics and should be considered when designing tasks to assess landing/cutting biomechanics. Coaches should therefore promote hamstring strength training and active trunk flexion during landing and cutting in an attempt to reduce ACL injury risk.Peer reviewe

Effect of axial tibial torque direction on ACL relative strain and strain rate in an in vitro simulated pivot landing

Anterior cruciate ligament (ACL) injuries most frequently occur under the large loads associated with a unipedal jump landing involving a cutting or pivoting maneuver. We tested the hypotheses that internal tibial torque would increase the anteromedial (AM) bundle ACL relative strain and strain rate more than would the corresponding external tibial torque under the large impulsive loads associated with such landing maneuvers. Twelve cadaveric female knees [mean (SD) age: 65.0 (10.5) years] were tested. Pretensioned quadriceps, hamstring, and gastrocnemius muscle‐tendon unit forces maintained an initial knee flexion angle of 15°. A compound impulsive test load (compression, flexion moment, and internal or external tibial torque) was applied to the distal tibia while recording the 3D knee loads and tibofemoral kinematics. AM‐ACL relative strain was measured using a 3 mm DVRT. In this repeated measures experiment, the Wilcoxon signed‐rank test was used to test the null hypotheses with p  < 0.05 considered significant. The mean (±SD) peak AM‐ACL relative strains were 5.4 ± 3.7% and 3.1 ± 2.8% under internal and external tibial torque, respectively. The corresponding mean (± SD) peak AM‐ACL strain rates reached 254.4 ± 160.1%/s and 179.4 ± 109.9%/s, respectively. The hypotheses were supported in that the normalized mean peak AM‐ACL relative strain and strain rate were 70 and 42% greater under internal than under external tibial torque, respectively ( p  = 0.023, p  = 0.041). We conclude that internal tibial torque is a potent stressor of the ACL because it induces a considerably (70%) larger peak strain in the AM‐ACL than does a corresponding external tibial torque. © 2011 Orthopaedic Research Society. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 30:528–534, 2012Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90222/1/21572_ftp.pd

Coupling angle variability in healthy and patellofemoral pain runners

Background Patellofemoral pain is hypothesized to result in less joint coordination variability. The ability to relate coordination variability to patellofemoral pain pathology could have many clinical uses; however, evidence to support its clinical application is lacking. The aim was to determine if vector coding's coupling angle variability, as a measure of joint coordination variability, was less for runners with patellofemoral pain than healthy controls as is commonly postulated. Methods Nineteen female recreational runners with patellofemoral pain and eleven healthy controls performed a treadmill acclimation protocol then ran at a self-selected pace for 15 min. 3-D kinematics, force plate kinetics, knee pain and rating of perceived exertion were recorded each minute. Data were selected for the: pain group at the highest pain reached (pain � 3/10) in a non-exerted state (exertion < 14/20), and; non-exerted healthy group from the eleventh minute. Coupling angle variability was calculated over several portions of the stride for six knee-ankle combinations during five non-consecutive strides. Findings 46 of 48 coupling angle variability measures were greater for the pain group, with 7 significantly greater (P <.05). Interpretation These findings oppose the theory that less coupling angle variability is indicative of a pathological coordinate state during running. Greater coupling angle variability may be characteristic of patellofemoral pain in female treadmill running when a larger threshold of pain is reached than previously observed. A predictable and directional response of coupling angle variability measures in relation to knee pathology is not yet clear and requires further investigation prior to considerations for clinical utility. © 2013 Elsevier Ltd

Accuracy and repeatability of wrist joint angles in boxing using an electromagnetic tracking system

© 2019, The Author(s). The hand-wrist region is reported as the most common injury site in boxing. Boxers are at risk due to the amount of wrist motions when impacting training equipment or their opponents, yet we know relatively little about these motions. This paper describes a new method for quantifying wrist motion in boxing using an electromagnetic tracking system. Surrogate testing procedure utilising a polyamide hand and forearm shape, and in vivo testing procedure utilising 29 elite boxers, were used to assess the accuracy and repeatability of the system. 2D kinematic analysis was used to calculate wrist angles using photogrammetry, whilst the data from the electromagnetic tracking system was processed with visual 3D software. The electromagnetic tracking system agreed with the video-based system (paired t tests) in both the surrogate ( 0.9). In the punch testing, for both repeated jab and hook shots, the electromagnetic tracking system showed good reliability (ICCs > 0.8) and substantial reliability (ICCs > 0.6) for flexion–extension and radial-ulnar deviation angles, respectively. The results indicate that wrist kinematics during punching activities can be measured using an electromagnetic tracking system

Dihedral Rewriteability

In this paper we compute the probability that an n-tuple for a group G is S-rewritable for a given set S of permutations for several classes of groups

The Concept of Divine Personhood in H. Richard Niebuhr's Thought

The major emphasis in this dissertation is on the development of H. Richard Niebuhr's concept of person as a key for understanding his approach to the theological problem of formulating the content of knowledge of God as it arises in the faith experience. This study begins with a brief introduction indicating the problematic character of the development of Niebuhr's concept of person, namely that while he clearly emphasized its centrality there is absent in his writings an explicit, formal statement that defines the conceptual content of what he intended by the term "person." The discussion that follows is an attempt to bring forward what seems to have been the content of Niebuhr's concept of person. This will involve the process of raising to prominence the "constants" that appear in his reflections on the relation between the divine and the human as relation between persons. The first chapter involves an investigation of the influence that the thought of Ernst Troeltsch, Karl Barth and others had on Niebuhr's own thinking. Therein is indicated the general framework of thought in which he had set for himself the task of providing for contemporary theology a means of expressing the content of faith so as to avoid the excesses of revelational dogmatism, on the one hand, and rationalistic relativism, on the other. The development of his approach--a personalistic confessionalism--appears in its general form in the second chapter, which involves a survey of his writings. The third chapter sets forth, as the cumulative effect of his writings, what appeared to be the essential components of Niebuhr's theological concept of person: act freedom, faithfulness, and dialogue. The fourth chapter indicates how Niebuhr seemed to have envisioned the role of this concept as a crucial, corrective principle for modifying such outstanding approaches to, the problem of knowledge of God as those of Troeltsch and Barth. This chapter also offers a suggestion as to what would be a consistent application of his thought to a development in theology since his death. The final chapter contains the present writer's response to certain critical reflections on Niebuhr's thought relevant to the central theme of the dissertation and a concluding section which suggests that the major emphasis and development of this discussion may be a modest but faithful and promising way to understand and appreciate more fully the essence of Niebuhr's complex and subtle thought.Doctor of Philosophy (PhD

Changes in knee kinematics reflect the articular geometry after arthroplasty

We hypothesized changes in rotations and translations after TKA with a fixed-bearing anterior cruciate ligament (ACL)-sacrificing but posterior cruciate ligament (PCL)-retaining design with equal-sized, circular femoral condyles would reflect the changes of articular geometry. Using 8 cadaveric knees, we compared the kinematics of normal knees and TKA in a standardized navigated position with defined loads. The quadriceps was tensed and moments and drawer forces applied during knee flexion-extension while recording the kinematics with the navigation system. TKA caused loss of the screw-home; the flexed tibia remained at the externally rotated position of normal full knee extension with considerably increased external rotation from 63° to 11° extension. The range of internal-external rotation was shifted externally from 30° to 20° extension. There was a small tibial posterior translation from 40° to 90° flexion. The varus-valgus alignment and laxity did not change after TKA. Thus, navigated TKA provided good coronal plane alignment but still lost some aspects of physiologic motion. The loss of tibial screw-home was related to the symmetric femoral condyles, but the posterior translation in flexion was opposite the expected change after TKA with the PCL intact and the ACL excised. Thus, the data confirmed our hypothesis for rotations but not for translations. It is not known whether the standard navigated position provides the best match to physiologic kinematics

In-vivo knee kinematics in rotationally unconstrained total knee arthroplasty.

Total knee replacement designs claim characteristic kinematic performance that is rarely assessed in patients. In the present study, in vivo kinematics of a new prosthesis design was measured during activities of daily living. This design is posterior stabilized for which spine-cam interaction coordinates free axial rotation throughout the flexion-extension arc by means of a single radius of curvature for the femoral condyles in the sagittal and frontal planes. Fifteen knees were implanted with this prosthesis, and 3D video-fluoroscopic analysis was performed at 6-month follow-up for three motor tasks. The average range of flexion was 70.1\ub0 (range: 60.1-80.2\ub0) during stair-climbing, 74.7\ub0 (64.6-84.8\ub0) during chair-rising, and 64.1\ub0 (52.9-74.3\ub0) during step-up. The corresponding average rotation on the tibial base-plate of the lines between the medial and lateral contact points was 9.4\ub0 (4.0-22.4\ub0), 11.4\ub0 (4.6-22.7\ub0), and 11.3\ub0 (5.1-18.0\ub0), respectively. The pivot point for these lines was found mostly in the central area of the base-plate. Nearly physiological range of axial rotation can be achieved at the replaced knee during activities of daily living

Evaluation of range of motion restriction within the hip joint

In Total Hip Arthroplasty, determining the impingement free range of motion requirement is a complex task. This is because in the native hip, motion is restricted by both impingement as well as soft tissue restraint. The aim of this study is to determine a range of motion benchmark which can identify motions which are at risk from impingement and those which are constrained due to soft tissue. Two experimental methodologies were used to determine motions which were limited by impingement and those motions which were limited by both impingement and soft tissue restraint. By comparing these two experimental results, motions which were limited by impingement were able to be separated from those motions which were limited by soft tissue restraint. The results show motions in extension as well as flexion combined with adduction are limited by soft tissue restraint. Motions in flexion, flexion combined with abduction and adduction are at risk from osseous impingement. Consequently, these motions represent where the maximum likely damage will occur in femoroacetabular impingement or at most risk of prosthetic impingement in Total Hip Arthroplasty