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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 |
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Journal Article |
| Year |
1995 |
Publication |
Ergonomics |
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| Volume |
38 |
Issue  |
9 |
Pages |
1894-1902 |
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| 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. |
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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 |
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Journal Article |
| Year |
1995 |
Publication |
Ergonomics |
Abbreviated Journal |
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| Volume |
38 |
Issue |
9 |
Pages |
1903-1910 |
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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. |
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58 |
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Falk, B.; Eliakim, A.; Dotan, R.; Liebermann, D.G.; Regev, R.; Bar-Or, O. |
| Title |
Birth weight and physical ability in 5- to 8-yr-old healthy children born prematurely |
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Journal Article |
| Year |
1997 |
Publication |
Medicine and Science in Sports and Exercise |
Abbreviated Journal |
Med Sci Sports Exerc |
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29 |
Issue |
9 |
Pages |
1124-1130 |
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*Birth Weight; Child; Child Development/physiology; Child, Preschool; Female; Follow-Up Studies; Humans; Infant, Newborn; *Infant, Premature; Male; *Motor Skills; *Physical Fitness |
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Recent advances in perinatal care have resulted in increased survival rates of extremely small and immature newborns. This has resulted in some neurodevelopmental impairment. The purpose of this study was to quantitatively evaluate and compare neuromuscular performance in children born prematurely at various levels of subnormal birth weight (BW). Subjects were 5- to 8-yr-old children born prematurely at different levels of subnormal BW (535-1760 g, N = 22, PM), and age-matched controls born at full term (> 2500 g, N = 15, CON). None of the subjects had any clinically defined neuromuscular disabilities. Body mass (BM) of PM was lower than that of CON (18.3 +/- 2.7 vs 21.7 +/- 3.8 kg) with no difference in height or sum of 4 skinfolds. Peak mechanical power output determined with a 15-s modified Wingate Anaerobic Test and corrected for BM was lower (P = 0.07) in PM than in CON (5.11 +/- 1.07 vs 5.94 +/- 1.00 W.kg-1). This was especially noticeable in children born at extremely low BW (ELBW, < 1000 g, 4.49 +/- 1.04 W.kg-1, P < 0.01). Peak power, determined in a force-plate vertical jump, corrected for BM was lower in PM vs CON (25.5 +/- 5.4 vs 30.8 +/- 5.2 W.kg-1, respectively P = 0.01), especially in the ELBW group (20.0 +/- 5.5 W.kg-1). Similarly, the elapsed time between peak velocity and actual jump take-off was longer in PM than in CON (41.2 +/- 9.4 vs 35.8 +/- 5.8 ms, respectively, P = 0.04). No differences were observed in peak force. The results suggest that performance deficiencies of prematurely-born children may be a result of inferior inter-muscular coordination. The precise neuromotor factors responsible for this should be identified by future research. |
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Ribstein Center for Research and Sport Medicine Sciences, Wingate Institute, Netanya, Israel. bfalk@ccsg.tau.ac.il |
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0195-9131 |
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PMID:9309621 |
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64 |
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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 |
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Journal Article |
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2012 |
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IEEE Transactions on Neural Systems and Rehabilitation Engineering : a Publication of the IEEE Engineering in Medicine and Biology Society |
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IEEE Trans Neural Syst Rehabil Eng |
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20 |
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6 |
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778-787 |
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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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1534-4320 |
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PMID:22907972 |
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28 |
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Liebermann, D.G.; Krasovsky, T.; Berman, S. |
| Title |
Planning maximally smooth hand movements constrained to nonplanar workspaces |
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Journal Article |
| Year |
2008 |
Publication |
Journal of Motor Behavior |
Abbreviated Journal |
J Mot Behav |
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40 |
Issue |
6 |
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516-531 |
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Adaptation, Physiological; Adult; Algorithms; Female; Hand/*physiology; Humans; *Intention; Kinesthesis/*physiology; Male; Models, Statistical; Movement/*physiology; Psychomotor Performance/*physiology; Reference Values; Writing |
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The article characterizes hand paths and speed profiles for movements performed in a nonplanar, 2-dimensional workspace (a hemisphere of constant curvature). The authors assessed endpoint kinematics (i.e., paths and speeds) under the minimum-jerk model assumptions and calculated minimal amplitude paths (geodesics) and the corresponding speed profiles. The authors also calculated hand speeds using the 2/3 power law. They then compared modeled results with the empirical observations. In all, 10 participants moved their hands forward and backward from a common starting position toward 3 targets located within a hemispheric workspace of small or large curvature. Comparisons of modeled observed differences using 2-way RM-ANOVAs showed that movement direction had no clear influence on hand kinetics (p < .05). Workspace curvature affected the hand paths, which seldom followed geodesic lines. Constraining the paths to different curvatures did not affect the hand speed profiles. Minimum-jerk speed profiles closely matched the observations and were superior to those predicted by 2/3 power law (p < .001). The authors conclude that speed and path cannot be unambiguously linked under the minimum-jerk assumption when individuals move the hand in a nonplanar 2-dimensional workspace. In such a case, the hands do not follow geodesic paths, but they preserve the speed profile, regardless of the geometric features of the workspace. |
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Department of Physical Therapy, The Stanley Steyer School of Health Professions, Sackler Faculty of Medicine, Tel Aviv University, Israel. dlieberm@post.tau.ac.il |
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0022-2895 |
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PMID:18980905 |
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33 |
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