172 research outputs found
The Effect of Exercise, Prewrap, and Athletic Tape on the Maximal Active and Passive Ankle Resistance to Ankle Inversion
This investigation explored alternatives to the null hy potheses that maximal active and passive resistance to inversion developed by a near-maximally inverted and weightbearing ankle is not altered by 1) the use of prophylactic adhesive athletic tape, 2) the use of non- adhesive prewrap (underwrap), or 3) 40 minutes of vigorous exercise. Ten healthy men and 10 healthy women (mean age, 25 ± 3 years) with no recent ankle injuries underwent testing to determine maximal ankle resistance to inversion under unipedal, weightbearing conditions. Tests were performed with and without the support of athletic tape, and before and after 40 min utes of exercise. Half the testing sessions were per formed with prewrap under the tape. At 15° of inver sion, without any external ankle support, healthy young men and women could maximally resist a mean (SD) inversion moment of 52.9 (6.4) N-m and 28.3 (5.8) N-m, respectively. Although use of ankle tape provided a 10% increase in maximal resistance to inversion moments, this increase diminished to insignificant lev els after 40 minutes of vigorous exercise. Use of pre wrap improved maximal resistance to inversion by more than 10%.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66568/2/10.1177_036354659702500203.pd
New perspectives on ACL injury: On the role of repetitive subĂą maximal knee loading in causing ACL fatigue failure
In this paper, we review a series of studies that we initiated to examine mechanisms of anterior cruciate ligament (ACL) injury in the hope that these injuries, and their sequelae, can be better prevented. First, using the earliest in vitro model of a simulated singleĂą leg jump landing or pivot cut with realistic knee loading rates and transĂą knee muscle forces, we identified the worstĂą case dynamic knee loading that causes the greatest peak ACL strain: Combined knee compression, flexion, and internal tibial rotation. We also identified morphologic factors that help explain individual susceptibility to ACL injury. Second, using the above knee loading, we introduced a possible paradigm shift in ACL research by demonstrating that the human ACL can fail by a sudden rupture in response to repeated subĂą maximal knee loading. If that load is repeated often enough over a short time interval, the failure tended to occur proximally, as observed clinically. Third, we emphasize the value of a physical exam of the hip by demonstrating how limited internal axial rotation at the hip both increases the susceptibility to ACL injury in professional athletes, and also increases peak ACL strain during simulated pivot landings, thereby further increasing the risk of ACL fatigue failure. When training atĂą risk athletes, particularly females with their smaller ACL crossĂą sections, rationing the number and intensity of worstĂą case knee loading cycles, such that ligament degradation is within the ACLâs ability to remodel, should decrease the risk for ACL rupture due to ligament fatigue failure.Ă© 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:2059Ăą 2068, 2016.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135588/1/jor23441.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/135588/2/jor23441_am.pd
Effect of increased quadriceps tensile stiffness on peak anterior cruciate ligament strain during a simulated pivot landing
ACL injury prevention programs often involve strengthening the knee muscles. We posit that an unrecognized benefit of such training is the associated increase in the tensile stiffness of the hypertrophied muscle. We tested the hypothesis that an increased quadriceps tensile stiffness would reduce peak anteromedial bundle (AMâ)ACL relative strain in female knees. Twelve female cadaver knees were subjected to compound impulsive twoâtimes body weight loads in compression, flexion, and internal tibial torque beginning at 15° flexion. Knees were equipped with modifiable custom springs to represent the nonlinear rapid stretch behavior of a normal and increased stiffness female quadriceps (i.e., 33% greater stiffness). Peak AMâACL relative strain was measured using an in situ transducer while muscle forces and tibiofemoral kinematics and kinetics were recorded. A 3D ADAMSâą dynamic biomechanical knee model was used in silico to interpret the experimental results which were analyzed using a repeatedâmeasures Wilcoxon test. Female knees exhibited a 16% reduction in peak AMâACL relative strain and 21% reduction in change in flexion when quadriceps tensile stiffness was increased by 33% (mean (SD) difference: 0.97% (0.65%), p â=â0.003). We conclude that increased quadriceps tensile stiffness reduces peak ACL strain during a controlled study simulating a pivot landing. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:423â430, 2014.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/102663/1/jor22531.pd
Can proprioception really be improved by exercises?
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41912/1/167-9-3-128_s001670100208.pd
Confidential Consortium Framework: Secure Multiparty Applications with Confidentiality, Integrity, and High Availability
Confidentiality, integrity protection, and high availability, abbreviated to
CIA, are essential properties for trustworthy data systems. The rise of cloud
computing and the growing demand for multiparty applications however means that
building modern CIA systems is more challenging than ever. In response, we
present the Confidential Consortium Framework (CCF), a general-purpose
foundation for developing secure stateful CIA applications. CCF combines
centralized compute with decentralized trust, supporting deployment on
untrusted cloud infrastructure and transparent governance by mutually untrusted
parties. CCF leverages hardware-based trusted execution environments for
remotely verifiable confidentiality and code integrity. This is coupled with
state machine replication backed by an auditable immutable ledger for data
integrity and high availability. CCF enables each service to bring its own
application logic, custom multiparty governance model, and deployment scenario,
decoupling the operators of nodes from the consortium that governs them. CCF is
open-source and available now at https://github.com/microsoft/CCF.Comment: 16 pages, 9 figures. To appear in the Proceedings of the VLDB
Endowment, Volume 1
OSSOS. VII. 800+Trans-Neptunian Objects-The Complete Data Release
The Outer Solar System Origins Survey (OSSOS), a wide-field imaging program in 2013-2017 with the Canada-France-Hawaii Telescope, surveyed 155 deg(2) of sky to depths of m(r) = 24.1-25.2. We present 838 outer solar system discoveries that are entirely free of ephemeris bias. This increases the inventory of trans-Neptunian objects (TNOs) with accurately known orbits by nearly 50%. Each minor planet has 20-60 Gaia/Pan-STARRS-calibrated astrometric measurements made over 2-5 oppositions, which allows accurate classification of their orbits within the trans-Neptunian dynamical populations. The populations orbiting in mean-motion resonance with Neptune are key to understanding Neptune's early migration. Our 313 resonant TNOs, including 132 plutinos, triple the available characterized sample and include new occupancy of distant resonances out to semimajor axis a similar to 130 au. OSSOS doubles the known population of the nonresonant Kuiper Belt, providing 436 TNOs in this region, all with exceptionally high-quality orbits of a uncertainty sigma(a)Peer reviewe
- âŠ