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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
Corporate Author Thesis
Publisher Place of Publication Editor
Language English Summary Language Original Title (up)
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0014-0139 ISBN Medium
Area Expedition Conference
Notes PMID:1800107 Approved no
Call Number Serial 55
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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
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
Corporate Author Thesis
Publisher Place of Publication Editor
Language English Summary Language Original Title (up)
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0264-0414 ISBN Medium
Area Expedition Conference
Notes PMID:7853452 Approved no
Call Number Serial 56
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Author Liebermann, D.G.; Ben-David, J.; Schweitzer, N.; Apter, Y.; Parush, A.
Title A field study of braking reactions during driving I: Triggering and modulation Type Journal Article
Year 1995 Publication Ergonomics Abbreviated Journal
Volume 38 Issue 9 Pages 1894-1902
Keywords
Abstract The present experiment was carried out to explore the response of driving subjects to emergency braking. The field trial consisted of driving behind a leading vehicle while the following drivers' responses were recorded by telemetry. A group of 51 individuals performed a series of trials at two driving speeds (60 and 80km/h), two following distances (6 and 12 m), and two braking conditions (real and dummy braking). Not all of these subjects completed all conditions or the minimum number of trials. The dependent variables were the total braking time (TBT) and its subcomponents: braking reaction time (BRT), and accelerator-to-brake movement time (MT). These data were analysed in three separate three-way ANOVAs with repeated measures on all factors. The results showed that when subjects were not aware of the forthcoming braking, the distance and braking conditions had major effects on all dependent variables. At the shorter following distance drivers reacted and moved faster. Similarly, when the brakes were real compared with dummy (i.e. brake lights only) drivers reacted faster. In addition, drivers reacted to onset of brake lights in 83% of the cases when dummy braking was applied, compared with 97% when real brakes were applied. Speed of driving did not show any significant effects and did not appear to influence the cognitive or attentional set to anticipate an emergency manoeuvre. These findings suggest that changes in angular velocity during optic expansion of the leading vehicle may be used as a cue to modulate braking movement, while onset of brake lights alone may be enough to trigger a ‘ballistic’ preventive response.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title (up)
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number Serial 57
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Author Schweitzer, N.; Apter, Y.; Ben-David, J.; Liebermann, D.G.; Parush, A.
Title A field study of braking reactions during driving II: Minimum driver braking times Type Journal Article
Year 1995 Publication Ergonomics Abbreviated Journal
Volume 38 Issue 9 Pages 1903-1910
Keywords
Abstract The minimum total braking time (i.e. the braking reaction time plus the accelerator-to-brake movement time) plays an important role in defining a minimum following gap (MFG). This study was designed to obtain a lower limit for this gap. Total braking times (TBT) of a group of 51 male and female young athletes were monitored during real driving conditions. Sudden braking applied by a leading private passenger vehicle initiated the trials. A within-subject design was used to study the effects of different factors on braking time. Individuals performed a series of semi-counterbalanced trials at two following distances (6 and 12 m), two speeds (60 and 80 km/h) and three expectancy stages (naïve driving, partial knowledge, and full knowledge of the forthcoming manoeuvre). A three-way repeated measures ANOVA showed no major effects of ‘speed’, but major effects of the ‘expectancy’ and the ‘distance’ factors. The experiment yielded a mean TBT of 0·678 s (SD = 0·144 s) for trials averaged over distances and speeds in the naïve condition only. The data emphasize the role played by pre-cues in the braking response prior to emergency stops. Both the level of awareness of the forthcoming manoeuvre and the distance between vehicles appear to determine the response time. The descriptive statistics presented may also provide the basis for an objective, acceptable and legally valid minimum time gap for prosecution of ‘careless’ drivers.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title (up)
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number Serial 58
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Author Tenenbaum, G.; Kohler, N.; Shraga, S.; Liebermann, D.G.; Lidor, R.
Title Anticipation and confidence of decisions related to skilled performance Type Journal Article
Year 1996 Publication Journal of Sport Psychology Abbreviated Journal
Volume 27 Issue Pages 293-307
Keywords
Abstract This study was carried out to examine anticipatory decisions of novice, intermediate, and expert tennis players and the confidence with which these decisions are made by these athletes. Perceived eye-focus was also measured to verify whether it is related to expertise level prior to action execution. Forty-five Australian players, 15 in each skill category, were exposed to 6 temporal occluded film conditions (480, 320, 160 ms prior to racquet-ball contact, at contact, and 160 and 320 ms after contact) in randomized order within 8 tennis strokes. In each condition, after viewing the filmed sequence, they were asked to report the final ball location of the opponent's stroke, how confident they were in this decision, and their perceived eye-focus location during the sequence. Experts and intermediates were superior in anticipatory decisions to their counterparts, only under short exposure durations. Novices showed more confidence than experts and intermediates at the beginning of the sequence, but after 160 and 320 ms of ball-racquet contact, experts were much more confident than novices, and intermediates. Self-reported eye-focus differed substantially with respect to expertise level. While experts attended to several locations prior to ball-racquet contact, intermediate and novice players gazed at one location. After contact, the reverse was evident. The findings are in partial agreement with other studies which have applied the temporal occlusion paradigm to study expert-novice differences in anticipatory skills.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title (up)
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number Serial 59
Permanent link to this record