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	Author	Liebermann, D.G.; Hoffman, J.R.
	Title	Timing of preparatory landing responses as a function of availability of optic flow information			Type	Journal Article
	Year	2005	Publication	Journal of Electromyography and Kinesiology : Official Journal of the International Society of Electrophysiological Kinesiology	Abbreviated Journal	J Electromyogr Kinesiol
	Volume	15	Issue	1	Pages	120-130
	Keywords	Adult; Cues; Electromyography; Humans; Male; Movement/physiology; Muscle, Skeletal/physiology; Posture/physiology; Psychomotor Performance/physiology; Vision, Ocular/*physiology
	Abstract	This study investigated temporal patterns of EMG activity during self-initiated falls with different optic flow information ('gaze directions'). Onsets of EMG during the flight phase were monitored from five experienced volunteers that completed 72 landings in three gaze directions (downward, mid-range and horizontal) and six heights of fall (10-130 cm). EMG recordings were obtained from the right gastrocnemius, tibialis anterior, biceps femoris and rectus femoris muscles, and used to determine the latency of onset (L(o)) and the perceived time to contact (T(c)). Impacts at touchdown were also monitored using as estimates the major peak of the vertical ground reaction forces (F(max)) normalized to body mass, time to peak (T(max)), peak impulse (I(norm)) normalized to momentum, and rate of change of force (dF(max)/dt). Results showed that L(o) was longer as heights of fall increased, but remained within a narrow time-window at >50 cm landings. No significant differences in L(o) were observed when gaze direction was changed. The relationship between T(c) and flight time followed a linear trend regardless of gaze direction. Gaze direction did not significantly affect the landing impacts. In conclusion, availability of optic flow during landing does not play a major role in triggering the preparatory muscle actions in self-initiated falls. Once a structured landing plan has been acquired, the relevant muscles respond relative to the start of the fall.
	Address	Department of Physical Therapy, Sackler Faculty of Medicine, Stanley Steyer School of Health Professions, University of Tel Aviv, Ramat Aviv, 69978 Tel Aviv, 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	1050-6411	ISBN		Medium
	Area		Expedition		Conference
	Notes	PMID:15642660			Approved	no
	Call Number				Serial	39
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	Author	Friedman, J.; Amiaz, A.; Korman, M.
	Title	The online and offline effects of changing movement timing variability during training on a finger-opposition task			Type	Journal Article
	Year	2022	Publication	Scientific Reports	Abbreviated Journal	Sci Rep
	Volume	12	Issue	1	Pages	13319
	Keywords	Fingers; Humans; Learning; Motor Skills; Movement; Psychomotor Performance; Upper Extremity
	Abstract	In motor learning tasks, there is mixed evidence for whether increased task-relevant variability in early learning stages leads to improved outcomes. One problem is that there may be a connection between skill level and motor variability, such that participants who initially have more variability may also perform worse on the task, so will have more room to improve. To avoid this confound, we experimentally manipulated the amount of movement timing variability (MTV) during training to test whether it improves performance. Based on previous studies showing that most of the improvement in finger-opposition tasks comes from optimizing the relative onset time of the finger movements, we used auditory cues (beeps) to guide the onset times of sequential movements during a training session, and then assessed motor performance after the intervention. Participants were assigned to three groups that either: (a) followed a prescribed random rhythm for their finger touches (Variable MTV), (b) followed a fixed rhythm (Fixed control MTV), or (c) produced the entire sequence following a single beep (Unsupervised control MTV). While the intervention was successful in increasing MTV during training for the Variable group, it did not lead to improved outcomes post-training compared to either control group, and the use of fixed timing led to significantly worse performance compared to the Unsupervised control group. These results suggest that manipulating MTV through auditory cues does not produce greater learning than unconstrained training in motor sequence tasks.
	Address
	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	2045-2322	ISBN		Medium
	Area		Expedition		Conference
	Notes	PMID:35922460; PMCID:PMC9349301			Approved	no
	Call Number				Serial	115
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	Author	Biess, A.; Flash, T.; Liebermann, D.G.
	Title	Riemannian geometric approach to human arm dynamics, movement optimization, and invariance			Type	Journal Article
	Year	2011	Publication	Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics	Abbreviated Journal	Phys Rev E Stat Nonlin Soft Matter Phys
	Volume	83	Issue	3 Pt 1	Pages	031927
	Keywords	Arm/physiology; Biomechanics; Computer Simulation; Humans; Kinetics; Male; Models, Biological; Models, Statistical; Models, Theoretical; Movement; Psychomotor Performance/physiology; Range of Motion, Articular/physiology; Reaction Time/physiology; Space Perception/physiology; Torque
	Abstract	We present a generally covariant formulation of human arm dynamics and optimization principles in Riemannian configuration space. We extend the one-parameter family of mean-squared-derivative (MSD) cost functionals from Euclidean to Riemannian space, and we show that they are mathematically identical to the corresponding dynamic costs when formulated in a Riemannian space equipped with the kinetic energy metric. In particular, we derive the equivalence of the minimum-jerk and minimum-torque change models in this metric space. Solutions of the one-parameter family of MSD variational problems in Riemannian space are given by (reparameterized) geodesic paths, which correspond to movements with least muscular effort. Finally, movement invariants are derived from symmetries of the Riemannian manifold. We argue that the geometrical structure imposed on the arm's configuration space may provide insights into the emerging properties of the movements generated by the motor system.
	Address	Bernstein Center for Computational Neuroscience, DE-37073 Gottingen, Germany. armin@nld.ds.mpg.de
	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	1539-3755	ISBN		Medium
	Area		Expedition		Conference
	Notes	PMID:21517543			Approved	no
	Call Number				Serial	29
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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
	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	Steinhart, S.; Weiss, P.L.; Friedman, J.
	Title	Proximal and distal movement patterns during a graphomotor task in typically developing children and children with handwriting problems			Type	Journal Article
	Year	2021	Publication	Journal of Neuroengineering and Rehabilitation	Abbreviated Journal	J Neuroeng Rehabil
	Volume	18	Issue	1	Pages	178
	Keywords	Arm; Biomechanical Phenomena; Child; Handwriting; Humans; Motor Skills; Movement; Upper Extremity; Distal joints; Handwriting; Motor control; Movement analysis; Proximal; Stability
	Abstract	BACKGROUND: Therapists specializing in handwriting difficulties in children often address motor problems including both proximal and distal movements in the upper extremity. Kinematic measures can be used to investigate various aspects of handwriting. This study examined differences in movement patterns in proximal and distal joints of the upper extremity during graphomotor tasks between typically developing children with and without handwriting problems. Additionally, it explored relationships between movement patterns, speed, and legibility of writing. METHODS: Forty-one children, aged 7-11 years, were assessed with the Aleph Aleph Ktav Yad Hebrew Handwriting assessment and the Beery Test of Visual Motor Integration and, based on their scores, were divided into a research group (with handwriting difficulties) and a control group (without handwriting difficulties). Upper extremity joint movement patterns were analyzed with a motion capture system. Differences in the quality of shapes traced and copied on a graphics tablet positioned horizontally and vertically were compared. Between-group differences and relationships with speed and legibility were analyzed. RESULTS: In both groups, there was greater movement in the distal compared to the proximal joints, greater movement when performing the task in a horizontal compared to a vertical plane, and greater movement when tracing than copying. Joint movements in the arm executed scaled-down versions of the shapes being drawn. While the amount of joint displacement was similar between groups, children in the research group showed greater dissimilarity between the drawn shape and the shape produced by the proximal joints. Finally, the drawing measure on the tablet was a significant predictor of legibility, speed of writing, visual motor integration and motor coordination, whereas the dissimilarity measure of joint movement was a significant predictor of speed of writing and motor coordination. CONCLUSIONS: This study provides support for the role of the distal upper extremity joints in the writing process and some guidance to assist clinicians in devising treatment strategies for movement-related handwriting problems. While we observed differences in proximal joint movements between the children with and without handwriting difficulties, the extent to which they are responsible for the differences in drawing quality remains to be determined. Further studies should use a similar methodology to examine additional tasks such as drawing shapes of varying sizes.
	Address	Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel. jason@tau.ac.il
	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	1743-0003	ISBN		Medium
	Area		Expedition		Conference
	Notes	PMID:34930334; PMCID:PMC8690895			Approved	no
	Call Number				Serial	118
Permanent link to this record