| Records |
Author  |
Liebermann, D.G.; Goodman, D. |
| Title |
Pre-landing muscle timing and post-landing effects of falling with continuous vision and in blindfold conditions |
Type |
Journal Article |
| Year |
2007 |
Publication |
Journal of Electromyography and Kinesiology : Official Journal of the International Society of Electrophysiological Kinesiology |
Abbreviated Journal |
J Electromyogr Kinesiol |
| Volume |
17 |
Issue |
2 |
Pages |
212-227 |
| Keywords |
Adult; Analysis of Variance; Biomechanics; *Blindness; *Electromyography; Humans; Joints/physiology; Lower Extremity/physiology; Male; Movement/*physiology; Muscle, Skeletal/*physiology; Orientation; *Vision, Ocular |
| Abstract |
The present study examined the effect of continuous vision and its occlusion in timing of pre-landing actions during free falls. When vision is occluded, muscle activation is hypothesized to start relative to onset of the fall. However, when continuous vision is available onset of action is hypothesized to be relative to the moment of touchdown. Six subjects performed 6 randomized sets of 6 trials after becoming familiar with the task. The 36 trials were divided in 2 visual conditions (vision and blindfold) and 3 heights of fall (15, 45 and 75 cm). EMG activity was recorded from the gastrocnemius and rectus femoris muscles during the falls. The latency of onset (L(o)) and the lapse from EMG onset to touchdown (T(c)) were obtained from these muscles. Vertical forces were recorded to assess the effects of pre-landing activity on the impacts at collision with and without continuous vision. Peak amplitude (F(max)), time to peak (T(max)) and peak impulse normalized to momentum (I(norm)) were used as outcome measures. Within flight time ranges of approximately 50-400 ms, the results showed that L(o) and T(c) follow a similar linear trend whether continuous vision was available or occluded. However, the variability of T(c) for each of the muscles was larger in the vision occluded condition. Analyses of variance showed that the rectus femoris muscle started consistently earlier in no vision trials. Finally, impact forces were not different in vision or blindfold conditions, and thus, they were not affected by minor differences in the timing of muscles prior to landing. Thus, it appears that knowing the surroundings before falling may help to reduce the need for a continuous visual input. The relevance of such input cannot be ruled out for falls from high landing heights, but cognitive factors (e.g., attention to specific cues and anticipation of a fall) may play a dominant role in timing actions during short duration falls encountered daily. |
| Address |
Physical Therapy Department, Sackler Faculty of Medicine, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel. dlieberm@post.tau.ac.il <dlieberm@post.tau.ac.il> |
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English |
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1050-6411 |
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| Notes |
PMID:16600637 |
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37 |
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| 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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0014-0139 |
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PMID:1800107 |
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55 |
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Liebermann, D.G.; Franks, I. M. |
| Title |
The use of feedback-based technologies in skill acquisition |
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Book Chapter |
| Year |
2004 |
Publication |
Notational analysis of Sport and Coaching Science |
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E & FN Spon Pub |
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Editor |
M. Hughes; I.M. Franks |
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45 |
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| Author |
Liebermann, D.G.; Franks I.M. |
| Title |
Video-feedback and information technologies |
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Book Chapter |
| Year |
2008 |
Publication |
Essentials of notational analysis |
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E & FN Spon Pub |
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I.M. Franks; M. Hughes |
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48 |
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| Author |
Liebermann, D.G.; Defrin, R. |
| Title |
Characteristics of the nociceptive withdrawal response elicited under aware and unaware conditions |
Type |
Journal Article |
| Year |
2009 |
Publication |
Journal of Electromyography and Kinesiology : Official Journal of the International Society of Electrophysiological Kinesiology |
Abbreviated Journal |
J Electromyogr Kinesiol |
| Volume |
19 |
Issue |
2 |
Pages |
e114-22 |
| Keywords |
Adult; Arm/*physiopathology; Attention; *Awareness; Cues; Female; Humans; Male; Movement; *Muscle Contraction; Muscle, Skeletal/*physiopathology; Pain/*physiopathology; *Reflex; *Startle Reaction |
| Abstract |
BACKGROUND: Nociceptive withdrawal reflexes (NWR) are subject to supraspinal modulation. Therefore, awareness about a noxious stimulation may affect its characteristics. The goal of this study was to investigate the effect of different degrees of awareness on the NWR. METHOD: Eight subjects performed back and forth hand movements from a common starting point towards four visual targets during which NWR was evoked when subjects were either unaware or aware of a noxious stimulation (unaware-NWR and aware-NWR). For the comparison between the NWR under both conditions, onset latencies and kinematic variables were computed respectively from the recorded Biceps Brachii EMG and from the spatial coordinates of hand reflective markers. RESULTS: The onset latency of unaware-NWR (mean+/-SD 73.9+/-13 ms) was significantly shorter than that of the aware-NWR (91.1+/-27 ms, p<0.05). The total duration of the muscular activation was shorter in unaware-NWR than in aware-NWR. The slopes of the tangential velocity-time curves were steeper for unaware-NWR than for aware-NWR (p=0.057). CONCLUSIONS: The results suggest that supraspinal regulation of NWR under different degrees of awareness involves the re-parameterization of selected spatiotemporal aspects of a pre-structured motor response. |
| Address |
Department of Physical Therapy, The Stanley Steyer School of Health Professions, Sackler Faculty of Medicine, Tel-Aviv University, Ramat Aviv, Tel Aviv 69978, Israel |
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English |
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Edition |
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1050-6411 |
ISBN |
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| Notes |
PMID:18063387 |
Approved |
no |
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Serial |
34 |
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