| Records |
| 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 |
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English |
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1050-6411 |
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| Notes |
PMID:15642660 |
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no |
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Serial |
39 |
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| Author |
Uri, O.; Pritsch, M.; Oran, A.; Liebermann, D.G. |
| Title |
Upper limb kinematics after arthroscopic and open shoulder stabilization |
Type |
Journal Article |
| Year |
2014 |
Publication |
Journal of Shoulder and Elbow Surgery |
Abbreviated Journal |
Journal of Shoulder and Elbow Surgery |
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Pages |
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Edition |
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| ISSN |
1058-2746 |
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no |
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75 |
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| Author |
Melzer, I.; Liebermann, D.G.; Krasovsky, T.; Oddsson, L.I.E. |
| Title |
Cognitive load affects lower limb force-time relations during voluntary rapid stepping in healthy old and young adults |
Type |
Journal Article |
| Year |
2010 |
Publication |
The Journals of Gerontology. Series A, Biological Sciences and Medical Sciences |
Abbreviated Journal |
J Gerontol A Biol Sci Med Sci |
| Volume |
65 |
Issue |
4 |
Pages |
400-406 |
| Keywords |
*Accidental Falls; Adult; Aged; Aged, 80 and over; Aging/*physiology; Attention/physiology; Cognition/*physiology; Gait/*physiology; Humans; Postural Balance/*physiology; Reaction Time |
| Abstract |
BACKGROUND: Quick step execution may prevent falls when balance is lost; adding a concurrent task delays this function. We investigate whether push-off force-time relations during the execution of rapid voluntary stepping is affected by a secondary task in older and young adults. METHODS: Nineteen healthy older adults and 12 young adults performed rapid voluntary stepping under single- and dual-task conditions. Peak power, peak force, and time to peak force during preparatory and swing phases of stepping were extracted from center of pressure and ground reaction force data. RESULTS: For dual-task condition compared with single-task condition, older adults show a longer time to reach peak force during the preparation and swing phases compared with young adults (approximately 25% vs approximately 10%, respectively). Peak power and peak force were not affected by a concurrent attention-demanding task. CONCLUSION: Older adults have difficulty allocating sufficient attention for fast muscle recruitment when concurrently challenged by an attention-demanding task. |
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Department of Physical Therapy, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel |
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English |
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Edition |
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| ISSN |
1079-5006 |
ISBN |
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| Notes |
PMID:19939911 |
Approved |
no |
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Serial |
50 |
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| Author |
Roijezon, U.; Djupsjobacka, M.; Bjorklund, M.; Hager-Ross, C.; Grip, H.; Liebermann, D.G. |
| Title |
Kinematics of fast cervical rotations in persons with chronic neck pain: a cross-sectional and reliability study |
Type |
Journal Article |
| Year |
2010 |
Publication |
BMC Musculoskeletal Disorders |
Abbreviated Journal |
BMC Musculoskelet Disord |
| Volume |
11 |
Issue |
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Pages |
222 |
| Keywords |
Adult; Aged; Biomechanics/*physiology; Cervical Vertebrae/*physiopathology; Chronic Disease; Cross-Sectional Studies; Female; Head Movements/*physiology; Humans; Middle Aged; Neck Pain/*diagnosis/*etiology/physiopathology; Physical Examination/methods; Reproducibility of Results; Rotation/*adverse effects; Time Factors; Young Adult |
| Abstract |
BACKGROUND: Assessment of sensorimotor function is useful for classification and treatment evaluation of neck pain disorders. Several studies have investigated various aspects of cervical motor functions. Most of these have involved slow or self-paced movements, while few have investigated fast cervical movements. Moreover, the reliability of assessment of fast cervical axial rotation has, to our knowledge, not been evaluated before. METHODS: Cervical kinematics was assessed during fast axial head rotations in 118 women with chronic nonspecific neck pain (NS) and compared to 49 healthy controls (CON). The relationship between cervical kinematics and symptoms, self-rated functioning and fear of movement was evaluated in the NS group. A sub-sample of 16 NS and 16 CON was re-tested after one week to assess the reliability of kinematic variables. Six cervical kinematic variables were calculated: peak speed, range of movement, conjunct movements and three variables related to the shape of the speed profile. RESULTS: Together, peak speed and conjunct movements had a sensitivity of 76% and a specificity of 78% in discriminating between NS and CON, of which the major part could be attributed to peak speed (NS: 226 +/- 88 degrees /s and CON: 348 +/- 92 degrees /s, p < 0.01). Peak speed was slower in NS compared to healthy controls and even slower in NS with comorbidity of low-back pain. Associations were found between reduced peak speed and self-rated difficulties with running, performing head movements, car driving, sleeping and pain. Peak speed showed reasonably high reliability, while the reliability for conjunct movements was poor. CONCLUSIONS: Peak speed of fast cervical axial rotations is reduced in people with chronic neck pain, and even further reduced in subjects with concomitant low back pain. Fast cervical rotation test seems to be a reliable and valid tool for assessment of neck pain disorders on group level, while a rather large between subject variation and overlap between groups calls for caution in the interpretation of individual assessments. |
| Address |
Centre for Musculoskeletal Research, University of Gavle, Sweden. ulrik.roijezon@ltu.se |
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English |
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1471-2474 |
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| Notes |
PMID:20875135 |
Approved |
no |
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Serial |
31 |
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| Author |
Liebermann, D.G.; Berman, S.; Weiss, P.L.T.; Levin, M.F. |
| Title |
Kinematics of reaching movements in a 2-d virtual environment in adults with and without stroke |
Type |
Journal Article |
| Year |
2012 |
Publication |
IEEE Transactions on Neural Systems and Rehabilitation Engineering : a Publication of the IEEE Engineering in Medicine and Biology Society |
Abbreviated Journal |
IEEE Trans Neural Syst Rehabil Eng |
| Volume |
20 |
Issue |
6 |
Pages |
778-787 |
| Keywords |
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| Abstract |
Virtual reality environments are increasingly being used for upper limb rehabilitation in poststroke patients. Our goal was to determine if arm reaching movements made in a 2-D video-capture virtual reality environment are similar to those made in a comparable physical environment. We compared arm and trunk kinematics for reaches made with the right, dominant arm to three targets (14 trials per target) in both environments by 16 adults with right poststroke hemiparesis and by eight healthy age-matched controls. Movement kinematics were recorded with a three-camera optoelectronic system at 100 samples/s. Reaching movements made by both control and stroke subjects were affected by viewing the targets in the video-capture 2-D virtual environment. Movements were slower, shorter, less straight, less accurate and involved smaller ranges of shoulder and elbow joint excursions for target reaches in the virtual environment compared to the physical environment in all subjects. Thus, there was a decrease in the overall movement quality for movements made in the 2-D virtual environment. This suggests that 2-D video-capture virtual reality environments should be used with caution when the goal of the rehabilitation program is to improve the quality of movement patterns of the upper limb. |
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English |
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Edition |
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| ISSN |
1534-4320 |
ISBN |
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| Notes |
PMID:22907972 |
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no |
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Serial |
28 |
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