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Author Hoffman, J.R.; Liebermann, D.; Gusis, A.
Title Relationship of leg strength and power to ground reaction forces in both experienced and novice jump trained personnel Type Journal Article
Year 1997 Publication Aviation, Space, and Environmental Medicine Abbreviated Journal (down) Aviat Space Environ Med
Volume 68 Issue 8 Pages 710-714
Keywords *Aerospace Medicine; *Aviation; Biomechanics; Humans; Leg/*physiology; Male; Military Personnel/*education; *Physical Education and Training; Physical Fitness/*physiology; Range of Motion, Articular; Wounds and Injuries/etiology/*prevention & control
Abstract METHODS: There were 14 male soldiers who participated in this study examining the relationship of leg strength and power on landing performance. Subjects were separated into two groups. The first group (E, n = 7) were parachute training instructors and highly experienced in parachute jumping. The second group of subjects (N, n = 7) had no prior parachute training experience and were considered novice jumpers. All subjects were tested for one-repetition maximum (1 RM) squat strength and maximal jump power. Ground reaction forces (GRF) and the time to peak force (TPF) at landing were measured from jumps at four different heights (95 cm, 120 cm, 145 cm, and 170 cm). All jumps were performed from a customized jump platform onto a force plate. RESULTS: No differences were seen between E and N in either IRM squat strength or in MJP. In addition, no differences were seen between the groups for time to peak force at any jump height. However, significantly greater GRF were observed in E compared to N. Moderate to high correlations between maximal jump power and GRF (r values ranging from 0.62-0.93) were observed in E. Although maximal jump power and the TPF was significantly correlated (r = -0.89) at only 120 cm for E, it was interesting to note that the correlations between MJP and the time to peak force in E were all negative and that the correlations between these variables in N were all positive. CONCLUSIONS: These results suggest that experienced parachutists may use a different landing strategy than novice jumpers. This difference may be reflected by differences in GRF generated during impact and a more efficient utilization of muscle power during the impact phase of the landing.
Address Aeromedical Center, Physiological Training Unit, Israel Air Force, Israel
Corporate Author Thesis
Publisher Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0095-6562 ISBN Medium
Area Expedition Conference
Notes PMID:9262813 Approved no
Call Number Serial 60
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Author Markstrom, J.L.; Liebermann, D.G.; Schelin, L.; Hager, C.K.
Title Atypical Lower Limb Mechanics During Weight Acceptance of Stair Descent at Different Time Frames After Anterior Cruciate Ligament Reconstruction Type Journal Article
Year 2022 Publication The American Journal of Sports Medicine Abbreviated Journal (down) Am J Sports Med
Volume Issue Pages 1-9
Keywords Acl; biomechanics; functional data analysis; motion analysis; stepping down
Abstract BACKGROUND: An anterior cruciate ligament (ACL) rupture may result in poor sensorimotor knee control and, consequentially, adapted movement strategies to help maintain knee stability. Whether patients display atypical lower limb mechanics during weight acceptance of stair descent at different time frames after ACL reconstruction (ACLR) is unknown. PURPOSE: To compare the presence of atypical lower limb mechanics during the weight acceptance phase of stair descent among athletes at early, middle, and late time frames after unilateral ACLR. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 49 athletes with ACLR were classified into 3 groups according to time after ACLR-early (<6 months; n = 17), middle (6-18 months; n = 16), and late (>18 months; n = 16)-and compared with asymptomatic athletes (control; n = 18). Sagittal plane hip, knee, and ankle angles; angular velocities; moments; and powers were compared between the ACLR groups' injured and noninjured legs and the control group as well as between legs within groups using functional data analysis methods. RESULTS: All 3 ACLR groups showed greater knee flexion angles and moments than the control group for injured and noninjured legs. For the other outcomes, the early group had, compared with the control group, less hip power absorption, more knee power absorption, lower ankle plantarflexion angle, lower ankle dorsiflexion moment, and less ankle power absorption for the injured leg and more knee power absorption and higher vertical ground reaction force for the noninjured leg. In addition, the late group showed differences from the control group for the injured leg revealing more knee power absorption and lower ankle plantarflexion angle. Only the early group took a longer time than the control group to complete weight acceptance and demonstrated asymmetry for multiple outcomes. CONCLUSION: Athletes with different time frames after ACLR revealed atypically large knee angles and moments during weight acceptance of stair descent for both the injured and the noninjured legs. These findings may express a chronically adapted strategy to increase knee control. In contrast, atypical hip and ankle mechanics seem restricted to an early time frame after ACLR. CLINICAL RELEVANCE: Rehabilitation after ACLR should include early training in controlling weight acceptance. Including a control group is essential when evaluating movement patterns after ACLR because both legs may be affected.
Address Department of Community Medicine and Rehabilitation, Physiotherapy, Umea University, Umea, Sweden
Corporate Author Thesis
Publisher Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0363-5465 ISBN Medium
Area Expedition Conference
Notes PMID:35604127 Approved no
Call Number Serial 112
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Author Flash, T.; Richardson, M. E.; Handzel, A. A.; Liebermann, D. G.
Title Computational Models and Geometric Approaches in Arm Trajectory Control Studies Type Book Chapter
Year 2003 Publication Progress in Motor Control III: From Basic Science to Applications Abbreviated Journal (down)
Volume Issue Pages
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Publisher Human Kinetics Place of Publication Champaign, Il Editor M. L. Latash; M. F. Levin
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number Serial 44
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Author Liebermann, D.G.; Franks, I. M.
Title The use of feedback-based technologies in skill acquisition Type Book Chapter
Year 2004 Publication Notational analysis of Sport and Coaching Science Abbreviated Journal (down)
Volume Issue Pages
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Corporate Author Thesis
Publisher E & FN Spon Pub Place of Publication Editor M. Hughes; I.M. Franks
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number Serial 45
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Author Carmeli E.; Liebermann, D.G.
Title The Function of the Aging Hand Type Book Chapter
Year 2007 Publication The Geriatric Rehabilitation Manual Abbreviated Journal (down)
Volume Issue Pages
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Publisher Elsevier Place of Publication NY Editor T. L. Kauffman; M. Moran; J. Barr
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number Serial 46
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