| Records |
| Author |
Liebermann, D.G.; Goodman, D. |
| Title |
Effects of visual guidance on the reduction of impacts during landings |
Type |
Journal Article |
| Year |
1991 |
Publication |
Ergonomics |
Abbreviated Journal  |
Ergonomics |
| Volume |
34 |
Issue |
11 |
Pages |
1399-1406 |
| Keywords |
Adult; Analysis of Variance; Biomechanics; *Cues; Humans; Male; Motor Activity/*physiology; Psychomotor Performance/physiology; Vision, Ocular/*physiology |
| Abstract |
While a common view is that vision is essential to motor performance, some recent studies have shown that continuous visual guidance may not always be required within certain time constraints. This study investigated a landing-related task (self-released falls) to assess the extent to which visual information enhances the ability to reduce the impacts at touchdown. Six individuals performed six blocked trials from four height categories in semi-counterbalanced order (5-10, 20-25, 60-65, and 90-95 cm) in vision and no-vision conditions randomly assigned. A series of two-way ANOVA with repeated measures were carried out separately on each dependent variable collapsed over six trials. The results indicated that vision during the flight did not produce softer landings. Indeed, in analysing the first peak (PFP) a main effect for visual condition was revealed in that the mean amplitude was slightly higher when vision was available (F(1,5) = 6.57; p less than 0.05), thus implicating higher forces at impact. The results obtained when the time to the first peak (TFP) was applied showed no significant differences between conditions (F(1,5) less than 1). As expected, in all cases, the analyses yielded significant main effects for the height categories factor. It appears that during self-initiated falls in which the environmental cues are known before the event, visual guidance is not necessary in order to adopt a softer landing strategy. |
| Address |
Research Department, Wingate Institute, Israel |
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| Language |
English |
Summary Language |
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Edition |
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| ISSN |
0014-0139 |
ISBN |
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| Notes |
PMID:1800107 |
Approved |
no |
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Serial |
55 |
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| Author |
Liebermann, D.G.; Levin, M.F.; McIntyre, J.; Weiss, P.L.; Berman, S. |
| Title |
Arm path fragmentation and spatiotemporal features of hand reaching in healthy subjects and stroke patients |
Type |
Journal Article |
| Year |
2010 |
Publication |
Conference Proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference |
Abbreviated Journal |
Conf Proc IEEE Eng Med Biol Soc |
| Volume |
2010 |
Issue |
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Pages |
5242-5245 |
| Keywords |
Aged; Aged, 80 and over; Analysis of Variance; Arm/*physiology; Biomechanics/physiology; Female; Hand/*physiology; *Health; Humans; Male; Middle Aged; Movement/*physiology; Posture/physiology; Principal Component Analysis; Stroke/*physiopathology; Time Factors |
| Abstract |
Arm motion in healthy humans is characterized by smooth and relatively short paths. The current study focused on 3D reaching in stroke patients. Sixteen right-hemiparetic stroke patients and 8 healthy adults performed 42 reaching movements towards 3 visual targets located at an extended arm distance. Performance was assessed in terms of spatial and temporal features of the movement; i.e., hand path, arm posture and smoothness. Differences between groups and within subjects were hypothesized for spatial and temporal aspects of reaching under the assumption that both are independent. As expected, upper limb motion of patients was characterized by longer and jerkier hand paths and slower speeds. Assessment of the number of sub-movements within each movement did not clearly discriminate between groups. Principal component analyses revealed specific clusters of either spatial or temporal measures, which accounted for a large proportion of the variance in patients but not in healthy controls. These findings support the notion of a separation between spatial and temporal features of movement. Stroke patients may fail to integrate the two aspects when executing reaching movements towards visual targets. |
| Address |
Physical Therapy Dept., Sackler Faculty of Medicine, Tel Aviv University, 69978 Israel. dlieberm@post.tau.ac.il |
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English |
Summary Language |
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Series Issue |
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Edition |
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| ISSN |
1557-170X |
ISBN |
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| Notes |
PMID:21096047 |
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no |
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Serial |
30 |
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| Author |
Melzer, I.; Krasovsky, T.; Oddsson, L.I.E.; Liebermann, D.G. |
| Title |
Age-related differences in lower-limb force-time relation during the push-off in rapid voluntary stepping |
Type |
Journal Article |
| Year |
2010 |
Publication |
Clinical Biomechanics (Bristol, Avon) |
Abbreviated Journal |
Clin Biomech (Bristol, Avon) |
| Volume |
25 |
Issue |
10 |
Pages |
989-994 |
| Keywords |
Accidental Falls/prevention & control; Age Factors; Aged; Aged, 80 and over; Aging/physiology; *Biomechanics; Female; Gait/*physiology; Humans; Male; *Postural Balance; Walking/*physiology |
| Abstract |
BACKGROUND: This study investigated the force-time relationship during the push-off stage of a rapid voluntary step in young and older healthy adults, to study the assumption that when balance is lost a quick step may preserve stability. The ability to achieve peak propulsive force within a short time is critical for the performance of such a quick powerful step. We hypothesized that older adults would achieve peak force and power in significantly longer times compared to young people, particularly during the push-off preparatory phase. METHODS: Fifteen young and 15 older volunteers performed rapid forward steps while standing on a force platform. Absolute anteroposterior and body weight normalized vertical forces during the push-off in the preparation and swing phases were used to determine time to peak and peak force, and step power. Two-way analyses of variance ('Group' [young-older] by 'Phase' [preparation-swing]) were used to assess our hypothesis (P </= 0.05). FINDINGS: Older people exerted lower peak forces (anteroposterior and vertical) than young adults, but not necessarily lower peak power. More significantly, they showed a longer time to peak force, particularly in the vertical direction during the preparation phase. INTERPRETATIONS: Older adults generate propulsive forces slowly and reach lower magnitudes, mainly during step preparation. The time to achieve a peak force and power, rather than its actual magnitude, may account for failures in quickly performing a preventive action. Such delay may be associated with the inability to react and recruit muscles quickly. Thus, training elderly to step fast in response to relevant cues may be beneficial in the prevention of falls. |
| Address |
Department of Physical Therapy, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel |
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English |
Summary Language |
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Series Title |
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Abbreviated Series Title |
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Series Issue |
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Edition |
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| ISSN |
0268-0033 |
ISBN |
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Expedition |
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Conference |
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| Notes |
PMID:20724044 |
Approved |
no |
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Serial |
51 |
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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 |
Summary Language |
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Edition |
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1471-2474 |
ISBN |
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Expedition |
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Conference |
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| Notes |
PMID:20875135 |
Approved |
no |
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Serial |
31 |
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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 |
Summary Language |
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Original Title |
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Series Title |
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Abbreviated Series Title |
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Series Issue |
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Edition |
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| ISSN |
0095-6562 |
ISBN |
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Expedition |
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Conference |
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| Notes |
PMID:9262813 |
Approved |
no |
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Serial |
60 |
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