Records |
Author |
Falk, B.; Eliakim, A.; Dotan, R.; Liebermann, D.G.; Regev, R.; Bar-Or, O. |
Title |
Birth weight and physical ability in 5- to 8-yr-old healthy children born prematurely |
Type |
Journal Article |
Year |
1997 |
Publication |
Medicine and Science in Sports and Exercise |
Abbreviated Journal |
Med Sci Sports Exerc |
Volume |
29 |
Issue |
9 |
Pages |
1124-1130 |
Keywords |
*Birth Weight; Child; Child Development/physiology; Child, Preschool; Female; Follow-Up Studies; Humans; Infant, Newborn; *Infant, Premature; Male; *Motor Skills; *Physical Fitness |
Abstract |
Recent advances in perinatal care have resulted in increased survival rates of extremely small and immature newborns. This has resulted in some neurodevelopmental impairment. The purpose of this study was to quantitatively evaluate and compare neuromuscular performance in children born prematurely at various levels of subnormal birth weight (BW). Subjects were 5- to 8-yr-old children born prematurely at different levels of subnormal BW (535-1760 g, N = 22, PM), and age-matched controls born at full term (> 2500 g, N = 15, CON). None of the subjects had any clinically defined neuromuscular disabilities. Body mass (BM) of PM was lower than that of CON (18.3 +/- 2.7 vs 21.7 +/- 3.8 kg) with no difference in height or sum of 4 skinfolds. Peak mechanical power output determined with a 15-s modified Wingate Anaerobic Test and corrected for BM was lower (P = 0.07) in PM than in CON (5.11 +/- 1.07 vs 5.94 +/- 1.00 W.kg-1). This was especially noticeable in children born at extremely low BW (ELBW, < 1000 g, 4.49 +/- 1.04 W.kg-1, P < 0.01). Peak power, determined in a force-plate vertical jump, corrected for BM was lower in PM vs CON (25.5 +/- 5.4 vs 30.8 +/- 5.2 W.kg-1, respectively P = 0.01), especially in the ELBW group (20.0 +/- 5.5 W.kg-1). Similarly, the elapsed time between peak velocity and actual jump take-off was longer in PM than in CON (41.2 +/- 9.4 vs 35.8 +/- 5.8 ms, respectively, P = 0.04). No differences were observed in peak force. The results suggest that performance deficiencies of prematurely-born children may be a result of inferior inter-muscular coordination. The precise neuromotor factors responsible for this should be identified by future research. |
Address |
Ribstein Center for Research and Sport Medicine Sciences, Wingate Institute, Netanya, Israel. bfalk@ccsg.tau.ac.il |
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English |
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ISSN |
0195-9131 |
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PMID:9309621 |
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no |
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Serial |
64 |
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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 |
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 |
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English |
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ISSN |
0095-6562 |
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Notes |
PMID:9262813 |
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no |
Call Number |
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Serial |
60 |
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Author |
Liebermann, D.G.; Krasovsky, T.; Berman, S. |
Title |
Planning maximally smooth hand movements constrained to nonplanar workspaces |
Type |
Journal Article |
Year |
2008 |
Publication |
Journal of Motor Behavior |
Abbreviated Journal |
J Mot Behav |
Volume |
40 |
Issue |
6 |
Pages |
516-531 |
Keywords |
Adaptation, Physiological; Adult; Algorithms; Female; Hand/*physiology; Humans; *Intention; Kinesthesis/*physiology; Male; Models, Statistical; Movement/*physiology; Psychomotor Performance/*physiology; Reference Values; Writing |
Abstract |
The article characterizes hand paths and speed profiles for movements performed in a nonplanar, 2-dimensional workspace (a hemisphere of constant curvature). The authors assessed endpoint kinematics (i.e., paths and speeds) under the minimum-jerk model assumptions and calculated minimal amplitude paths (geodesics) and the corresponding speed profiles. The authors also calculated hand speeds using the 2/3 power law. They then compared modeled results with the empirical observations. In all, 10 participants moved their hands forward and backward from a common starting position toward 3 targets located within a hemispheric workspace of small or large curvature. Comparisons of modeled observed differences using 2-way RM-ANOVAs showed that movement direction had no clear influence on hand kinetics (p < .05). Workspace curvature affected the hand paths, which seldom followed geodesic lines. Constraining the paths to different curvatures did not affect the hand speed profiles. Minimum-jerk speed profiles closely matched the observations and were superior to those predicted by 2/3 power law (p < .001). The authors conclude that speed and path cannot be unambiguously linked under the minimum-jerk assumption when individuals move the hand in a nonplanar 2-dimensional workspace. In such a case, the hands do not follow geodesic paths, but they preserve the speed profile, regardless of the geometric features of the workspace. |
Address |
Department of Physical Therapy, The Stanley Steyer School of Health Professions, Sackler Faculty of Medicine, Tel Aviv University, Israel. dlieberm@post.tau.ac.il |
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English |
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Edition |
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ISSN |
0022-2895 |
ISBN |
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Notes |
PMID:18980905 |
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no |
Call Number |
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Serial |
33 |
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Author |
Issurin, V.B.; Liebermann, D.G.; Tenenbaum, G. |
Title |
Effect of vibratory stimulation training on maximal force and flexibility |
Type |
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Year |
1994 |
Publication |
Journal of Sports Sciences |
Abbreviated Journal |
J Sports Sci |
Volume |
12 |
Issue |
6 |
Pages |
561-566 |
Keywords |
Adult; Humans; Male; Muscle Contraction/physiology; Muscle, Skeletal/*physiology; *Physical Education and Training; Vibration/*therapeutic use |
Abstract |
In this study, we investigated a new method of training for maximal strength and flexibility, which included exertion with superimposed vibration (vibratory stimulation, VS) on target muscles. Twenty-eight male athletes were divided into three groups, and trained three times a week for 3 weeks in one of the following conditions: (A) conventional exercises for strength of the arms and VS stretching exercises for the legs; (B) VS strength exercises for the arms and conventional stretching exercises for the legs; (C) irrelevant training (control group). The vibration was applied at 44 Hz while its amplitude was 3 mm. The effect of training was evaluated by means of isotonic maximal force, heel-to-heel length in the two-leg split across, and flex-and-reach test for body flexion. The VS strength training yielded an average increase in isotonic maximal strength of 49.8%, compared with an average gain of 16% with conventional training, while no gain was observed for the control group. The VS flexibility training resulted in an average gain in the legs split of 14.5 cm compared with 4.1 cm for the conventional training and 2 cm for the control groups, respectively. The ANOVA revealed significant pre-post training effects and an interaction between pre-post training and 'treatment' effects (P < 0.001) for the isotonic maximal force and both flexibility tests. It was concluded that superimposed vibrations applied for short periods allow for increased gains in maximal strength and flexibility. |
Address |
Ribstein Centre for Research and Sport Medicine Sciences, Wingate Institute, Wingate Post, Israel |
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English |
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Series Issue |
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Edition |
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ISSN |
0264-0414 |
ISBN |
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Conference |
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Notes |
PMID:7853452 |
Approved |
no |
Call Number |
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Serial |
56 |
Permanent link to this record |
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Author |
Biess, A.; Liebermann, D.G.; Flash, T. |
Title |
A computational model for redundant human three-dimensional pointing movements: integration of independent spatial and temporal motor plans simplifies movement dynamics |
Type |
Journal Article |
Year |
2007 |
Publication |
The Journal of Neuroscience : the Official Journal of the Society for Neuroscience |
Abbreviated Journal |
J Neurosci |
Volume |
27 |
Issue |
48 |
Pages |
13045-13064 |
Keywords |
Analysis of Variance; Arm/physiology; Biomechanics; *Computer Simulation; Humans; *Models, Biological; Movement/*physiology; *Nonlinear Dynamics; Posture/physiology; Psychomotor Performance/*physiology; Range of Motion, Articular/physiology; Reaction Time/physiology; Space Perception/*physiology; Time Factors; Torque |
Abstract |
Few computational models have addressed the spatiotemporal features of unconstrained three-dimensional (3D) arm motion. Empirical observations made on hand paths, speed profiles, and arm postures during point-to-point movements led to the assumption that hand path and arm posture are independent of movement speed, suggesting that the geometric and temporal properties of movements are decoupled. In this study, we present a computational model of 3D movements for an arm with four degrees of freedom based on the assumption that optimization principles are separately applied at the geometric and temporal levels of control. Geometric properties (path and posture) are defined in terms of geodesic paths with respect to the kinetic energy metric in the Riemannian configuration space. Accordingly, a geodesic path can be generated with less muscular effort than on any other, nongeodesic path, because the sum of all configuration-speed-dependent torques vanishes. The temporal properties of the movement (speed) are determined in task space by minimizing the squared jerk along the selected end-effector path. The integration of both planning levels into a single spatiotemporal representation simplifies the control of arm dynamics along geodesic paths and results in movements with near minimal torque change and minimal peak value of kinetic energy. Thus, the application of Riemannian geometry allows for a reconciliation of computational models previously proposed for the description of arm movements. We suggest that geodesics are an emergent property of the motor system through the exploration of dynamical space. Our data validated the predictions for joint trajectories, hand paths, final postures, speed profiles, and driving torques. |
Address |
Department of Mathematics, Weizmann Institute of Science, 76100 Rehovot, Israel. armin.biess@weizmann.ac.il |
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English |
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Series Issue |
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Edition |
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ISSN |
0270-6474 |
ISBN |
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Conference |
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Notes |
PMID:18045899 |
Approved |
no |
Call Number |
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Serial |
35 |
Permanent link to this record |