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PubMed2004

Vehicle speed affects both pre-skid braking kinematics and average tire/roadway friction.

Vehicles decelerate between brake application and skid onset. To better estimate a vehicle's speed and position at brake application, we investigated how vehicle deceleration varied with initial speed during both the pre-skid and skidding intervals on dry asphalt. Skid-to-stop tests were performed from four initial speeds (20, 40, 60, and 80 km/h) using three different grades of tire (economy, touring, and performance) on a single vehicle and a single road surface. Average skidding friction was found to vary with initial speed and tire type. The post-brake/pre-skid speed loss, elapsed time, distance travelled, and effective friction were found to vary with initial speed. Based on these data, a method using skid mark length to predict vehicle speed and position at brake application rather than skid onset was shown to improve estimates of initial vehicle speed by up to 10 km/h and estimates of vehicle position at brake application by up to 8 m compared to conventional methods that ignore the post-brake/pre-skid interval.

Automobile Driving↗
PubMed2002

Driving simulator validation for speed research.

The behavioral validation of an advanced driving simulator for its use in evaluating speeding countermeasures was performed for mean speed. Using mature drivers, 24 participants drove an instrumented car and 20 participants drove the simulator in two separate experiments. Participants drove on roads which contained transverse rumble strips at three sites, as well as three equivalent control sites. The three pairs of sites involved deceleration, and were the approaches to stop sign intersections, right curves, and left curves. Numerical correspondence (absolute validity), relative correspondence (or validity), and interactive (or dynamic) relative validity were analyzed, the latter using correlations developed from canonical correlation. Participants reacted to the rumble strips, in relation to their deceleration pattern on the control road, in very similar ways in both the instrumented car and simulator experiments, establishing the relative validities. However, participants generally drove faster in the instrumented car than the simulator, resulting in absolute validity not being established.

Adult↗
PubMed1997

Evaluation of an alternative traffic light change anticipation system.

A driving simulator was used to study the efficacy of an alternative signal phasing program. The new Traffic Light Change Anticipation System (TLCAS) utilizes a flashing amber in conjunction with a solid green indication to warn drivers of the impending onset of the solid amber indication. This new program was expected to provide drivers with additional information with which to make safe stopping or crossing decisions, and reduce behaviour associated with increased accident rates at signalized intersections. Additionally, a new measure of first response variability was introduced to evaluate the effect of the new program on driver behavior. The results indicated that the new system has the ability to reduce the number of red light violations. Of the 1148 target intersections, 43 violations were recorded for the regular program compared to 9 for the TLCAS program. The severity of decelerations was also impacted. The regular program displayed average maximum decelerations of 3.1 m/sec2 compared to 2.5 m/sec2 for the TLCAS program. However, the TLCAS program showed an increased variability in first response five times larger than the regular program. This finding, in conjunction with traditional measures, indicates that the new system performs comparably to an increased amber duration by increasing the potential for conflicting decisions between successive drivers approaching an intersection. Altogether, the results suggest that this alternative signal phasing program would not improve intersection safety. The findings also suggest that further study of the longitudinal behavior after the introduction of a TLCAS program may be warranted. Specifically, future studies should examine whether subjects engage in appropriate adaptive changes when confronted with a solid amber period warning after becoming familiar with the TLCAS.

Accidents, Traffic↗
PubMed2005

Calibration, information, and control strategies for braking to avoid a collision.

This study explored visual control strategies for braking to avoid collision by manipulating information about speed of self-motion. Participants watched computer-generated displays and used a brake to stop at an object in the path of motion. Global optic flow rate and edge rate were manipulated by adjusting eye-height and ground-texture size. Stopping distance, initiation of braking, and the magnitude of brake adjustments were influenced by both optical variables, but global optic flow rate had a stronger effect. A new model is introduced according to which braking is controlled by keeping the perceived ideal deceleration, based in part on global optic flow rate, within a "safe" region between 0 and the maximum deceleration of the brake.

Adolescent↗
PubMed1993

In vivo examination of the dynamic properties of the human heel pad.

The shock-absorbing characteristics of the heel pad in vivo were examined in adults (N = 16) and 7-year-old children (N = 5) using a drop-impact tester (wt = 5 kg). Impact velocities were 0.72 m/s and 0.93 m/s. It was found that in adults the average peak deceleration was 11.6 G at an impact velocity of 0.93 m/s. The maximum deformation of the heel pad was 11.3 mm, and the computed energy absorption during impact amounted to 79% (range = 75%-89%). These mechanical characteristics remained nearly the same even after 6 min of repeated impacts by the impact tester and even after a 10 km run. The children had larger values of peak deceleration and maximum deformation and smaller energy loss than the adults. It was concluded that the heel pad was a fairly effective shock attenuator and high energy absorber, and that these characteristics remain nearly unchanged even after a relatively long period of repeated impacts. It was also concluded that the mechanical properties of the children's heel pads were different from those of the adults.

Acceleration↗
PubMed1999

Neonatal platelet counts in fetal brain injury.

UNLABELLED: The objective of this study was to determine whether neonatal platelet counts can be used in fetal brain injury. The initial platelet counts, expressed as 1000 per mm3, of singleton term infants with and without permanent asphyxial brain injury were compared. Neonates with encephalopathy were divided into 3 groups: I--nonreactive fetal heart rate (FHR) pattern from admission until delivery; II--reactive FHR pattern on admission followed by nonreactivity, tachycardia, a loss of variability and repetitive FHR decelerations; and III--acute: reactive FHR pattern followed by a sudden prolonged FHR deceleration that lasted until delivery. The neonates and platelet counts for each group were as follows: CONTROL: 104 neonates, mean 281 +/- 56, range 154 to 411; I: 60, mean 185 +/- 80, range 28 to 365; II: 34, mean 251 +/- 66, range 100 to 375; and III: 35, mean 267 +/- 93, range 86 to 569. Platelet counts were significantly lower in neonates with encephalopathy (p <0.001). Group I differed statistically from both Groups II and III (p <0.001). These data suggest an association between the FHR pattern, fetal asphyxial brain injury, and the initial platelet count in singleton term neonates. Further investigation should be pursued to clarify the physiological processes leading to this result.

Brain Diseases↗
PubMed2026

External load metrics and monitoring in women's football match play: A systematic review.

This systematic review aimed to identify the most commonly used variables for monitoring external load during elite women's football matches and to compare reporting practices internationally and in Brazil. Searches were conducted in Web of Science, PubMed, and SciELO using the PICOS framework between February and March 2026, resulting in the inclusion of 35 studies. The main outcomes analysed were total distance covered (TD), distance covered across speed zones (HSR, VHSR, sprint), number of accelerations and decelerations, and maximum speed. TD and distance covered across speed zones were the most frequently reported indicators (94.3%), followed by HSR (82.8%) and sprint distance (68.5%). Considerable variability was observed in the classification of speed zones and thresholds used to define accelerations and decelerations, limiting comparisons between studies. External load values varied according to playing position and competition level, with international matches generally imposing greater demands than national competitions. Brazilian research remains limited and demonstrates notable methodological variability. This review proposes standardised speed and acceleration/deceleration thresholds based on the most recurrent ranges reported in the literature, supporting improved consistency in monitoring practices across elite women's football contexts.

Humans↗
PubMed1997

Visual control of braking in goal-directed action and sport.

Reaching a moving object, avoiding an obstacle, or controlling a rotation are common requirements of experts in sport and goal-directed action. Since the original analysis of optic flow, a large number of studies have addressed the problem of perception and control of braking. In this paper, the perception-action strategies described for deceleration control are reviewed; driving, docking, landing, somersaulting, running and reaching are analysed. The role played by 'tau dot', the first temporal derivative of tau, is shown to be critical. However, the so-called constant tau-dot strategy proposed to explain how we regulate our deceleration in such circumstances is critically examined and rejected. New directions in the problem of braking control are proposed that emphasize: (1) the advantage of tau-dot over other kinematic variables; (2) the task specificity of tau-dot; (3) the need to consider tau-dot as a control variable; and (4) the role played by the controller dynamics in the perception-action loop. Several directions for future research are suggested.

Animals↗
PubMed1998

Effects of tennis practice on the coincidence timing accuracy of adults and children.

This study examines the development of perceptuomotor processes involved in coincidence timing tasks according to age and experience in tennis. Tennis players and novices, 7, 10, 13, and 23 years of age, were tested in a coincidence timing task which consisted of estimating the arrival of a simulated moving object on a target. The effect of three different motions were analyzed: constant velocity, constant acceleration, and constant deceleration. Results showed that (1) timing accuracy improves mainly between the ages of 7 and 10 years; (2) tennis practice accelerates the development of timing accuracy; and (3) acceleration or deceleration of the moving stimulus had no effect on the timing accuracy of any of the tested groups, suggesting a continuous visual control of the trajectory. Theoretical implications for the development of perceptuomotor processes involved in coincidence timing tasks are discussed.

Acceleration↗
PubMed1996

Routine transesophageal echocardiography for the diagnosis of aortic disruption in trauma patients without enlarged mediastinum.

OBJECTIVE: To assess the value of routine transesophageal echocardiography (TEE) in diagnosing traumatic disruption of the aorta (TDA) in trauma patients presenting without enlarged mediastinum on chest x-ray films. DESIGN: Prospective study. MATERIALS AND METHODS: TEE was routinely performed to exclude the presence of TDA in patients who sustained severe trauma secondary to abrupt deceleration collisions and presented with an upper mediastinum of fewer than 8 cm on supine chest x-ray films. Patients were divided into two groups according to the presence (group I) or absence (group II) of mediastinal hematoma diagnosed during TEE examination. Radiographic signs regarded as indicators of the presence of TDA were evaluated in both groups. RESULTS: Among the 40 consecutive patients studied, TEE demonstrated two cases of TDA associated with a mediastinal hematoma that were confirmed by both aortography and surgery. One of the patients had a normal mediastinum on presentation chest x-ray films, and the other only exhibited a blurred aortic knob. Radiographic mediastinal abnormalities suggestive of TDA were observed in 13 patients, but chest x-ray films were unremarkable in 12 patients. Twenty patients had multiple rib fractures. The frequency of chest radiographic abnormalities was not significantly higher in group I (n = 6) when compared with group II patients (n = 34). TEE examination demonstrated a normal thoracic aorta in 35 patients and was nondiagnostic in 3 patients (normal aortography). CONCLUSION: TEE should be routinely performed in victims of violent deceleration collisions, even in patients presenting apparently normal mediastinum on supine chest radiography.

Accidents, Traffic↗
PubMed1998

In vitro attenuation of impact shock in equine digits.

This study was designed to test the impact characteristics of the equine digit in vitro with the objective of providing a better understanding of the role of the digital structures in the attenuation of impact shock. Uni-axial accelerometers were mounted on cadaver digits on the distolateral hoof wall, the proximolateral hoof wall, the dorsal surface of the second phalanx, and the mid-lateral first phalanx. The hoof-mounted accelerometers were aligned with the hoof tubules while the bone-mounted accelerometers were oriented along the longitudinal axis of the bone. Each digit was mounted in a test apparatus designed to simulate impact of the hoof with the ground during locomotion. The digits were subjected to 3 impact trials against a barrier at each of 3 vertical impact velocities that simulated a forward trotting velocity in the range of 2.67 to 4.46 m/s. The impact deceleration tended to increase with impact velocity. Attenuation of the impact shock by the digital tissues resulted in a reduction in impact decleration in the more proximal measuring locations. The interphalangeal joints appeared to play a larger role in amplitude attenuation than the hoof wall or the soft tissue structures within the hoof wall. The signal frequency data showed that the soft tissues within the hoof acted as a 'lowpass' filter, attenuating the higher deceleration frequencies. The hoof wall and the interphalangeal joints showed little frequency attenuation.

Animals↗
PubMed1990

A proposed new mechanism of traumatic aortic rupture: the osseous pinch.

The currently accepted mechanism to explain traumatic aortic rupture from rapid deceleration involves a combination of traction, torsion, and hydrostatic forces. The authors hypothesize that aortic isthmus lacerations result from a pinch of the aorta between the spine and the anterior bony thorax (manubrium, clavicle, and first ribs) during chest compression caused by abrupt deceleration. Compression of an articulated, normally moving thoracic skeleton containing a synthetic aorta consistently caused transection of the aorta at the isthmus between the spine and anterior bony structures. Analysis of rotation of the first rib in 10 consecutive patients undergoing computed tomography of the chest demonstrated interposition of the distal aortic arch and isthmus between the vertebrae and anterior bony thorax in each instance. Aortas excised from laboratory dogs were pinched between structures simulating bones to reproduce intimal and medial lesions indistinguishable from lesions associated with naturally occurring traumatic disruptions. Although further studies in cadaveric specimens are necessary to confirm this mechanism of injury, the authors believe that their results support the osseous-pinch mechanism of aortic rupture.

Animals↗
PubMed2003

A feedback-controlled treadmill (treadmill-on-demand) and the spontaneous speed of walking and running in humans.

A novel apparatus, composed by a controllable treadmill, a computer, and an ultrasonic range finder, is here proposed to help investigation of many aspects of spontaneous locomotion. The acceleration or deceleration of the subject, detected by the sensor and processed by the computer, is used to accelerate or decelerate the treadmill in real time. The system has been used to assess, in eight subjects, the self-selected speed of walking and running, the maximum "reasonable" speed of walking, and the minimum reasonable speed of running at different gradients (from level up to +25%). This evidenced the speed range at which humans neither walk nor run, from 7.2 +/- 0.6 to 8.4 +/- 1.1 km/h for level locomotion, slightly narrowing at steeper slopes. These data confirm previous results, obtained indirectly from stride frequency recordings. The self-selected speed of walking decreases with increasing gradient (from 5.0 +/- 0.8 km/h at 0% to 3.0 +/- 0.9 km/h at +25%) and seems to be approximately 30% higher than the speed that minimizes the metabolic energy cost of walking, obtained from the literature, at all the investigated gradients. The advantages, limitations, and potential applications of the newly proposed methodology in physiology, biomechanics, and pathology of locomotion are discussed in this paper.

Acceleration↗
PubMed1991

Dynamic characteristics of a sport wheelchair.

A single subject performed 36 coast-down trials on a hardwood floor in a sport model wheelchair with velocity ranging from 1.28 to 5.31 m/s (4.6 to 19.1 km/h). A portable computer attached to the wheelchair was used to record the time to the nearest 0.001-second of each half-revolution of a rear wheel. The deceleration during each trial was determined with an average coefficient of variation of 2.6 percent from linear regression of velocity versus time values. A significant relationship (r = 0.97) between deceleration and the square of the velocity was noted in an analysis of the values from the 36 trials. Total drag force and power was calculated as a function of wheelchair velocity from this relationship, indicating that the power output needed to propel the wheelchair increased as a function of the velocity cubed. It is speculated that this noted exponential increase in the energy cost of wheelchair propulsion at higher speeds was due mainly to an increase in air drag.

Acceleration↗
PubMed2001

The effect of upper-limb motion on lower-limb muscle synchrony. Implications for anterior cruciate ligament injury.

BACKGROUND: A high prevalence of rupture of the anterior cruciate ligament is associated with activities that incorporate both abrupt deceleration and catching a ball. In the present study, we examined whether the upper-limb motion involved in catching a ball affected the synchrony of the lower-limb muscles during tasks known to stress the anterior cruciate ligament-namely, abrupt decelerative landings. METHODS: Seven male and eleven female subjects decelerated abruptly to land in single-limb stance after catching a chest-height pass and after no catching. Ground-reaction force and electromyographic data for six lower-limb muscles were sampled while the subjects' landing technique was filmed. The joint-reaction forces and the sagittal planar net moments for the knee then were calculated to derive the tibiofemoral shear forces. The muscle onsets and peak muscle activities were temporally analyzed with respect to the time of initial foot-ground contact, the peak resultant ground-reaction force, and the peak tibiofemoral shear force. RESULTS: When catching a pass, the subjects demonstrated significantly (p < 0.05) earlier rectus femoris onset relative to the timing of the initial foot-ground contact and of the peak tibiofemoral shear force, and they showed delayed biceps femoris onset relative to the timing of the peak tibiofemoral shear force compared with the findings in the trials without catching. CONCLUSIONS: We concluded that catching a ball during an abrupt landing could increase the potential for an anterior cruciate ligament injury by limiting the time available for the hamstring muscles to generate posterior tibial-drawer force before the onset of the quadriceps-induced anterior tibial translation. CLINICAL RELEVANCE: The integrity of the anterior cruciate ligament during landing relies on the proper coordination of the lower-limb muscles, particularly the quadriceps and the hamstrings. The present study demonstrated that motion of the upper-limbs may interfere with recruitment of these muscles, thereby predisposing the anterior cruciate ligament to injury.

Adult↗
PubMed1990

Perceptual inequality between two physically equal constant velocities.

When an object moves with an equal constant velocity before and after passing through a tunnel (or before and after a sudden acceleration--or deceleration--in the central part of its trajectory), the two velocities (the one preceding and the one following the tunnel or the sudden acceleration or deceleration) are perceived as different even if actually physically equal. Four experiments were carried out to underestimation of the second velocity (i.e., the one following the tunnel) when the first one (i.e., the one preceding the tunnel) is low, and an overestimation of the second one when the values of the first velocity are higher. An interpretation of the results is proposed, suggesting that an appearance effect (i.e., an apparent higher velocity at the beginning of the movement) could be for the perceptual inequality between the two physically equal constant velocities.

Attention↗
PubMed2003

The influence of object-image velocity change on perceived heading in minimal environments.

When human observers move forward and rotate their eyes, a complex pattern of light flows across the retina. This pattern is referred to as retinal flow. A model has been proposed to explain how humans perceive their direction of self-movement (or heading) from (1) static depth, (2) direction of image motion, and (3) whether image velocity undergoes acceleration or deceleration (Wang & Cutting, 1999). However, findings from past research in which sparse or minimalist stimuli were used have suggested that not all of the information to which participants are sensitive is captured within the scope of this model. In particular it has been suggested that the magnitude or size of image velocity change may be of significance beyond simply whether image velocity could be categorized as speeding up (i.e., accelerating) or slowing down (i.e., decelerating). In two experiments, the influence of this factor on heading judgments under minimal conditions was investigated. Evidence was found in support of the idea that the rate of image velocity change can influence judgments of the direction of self-movement in minimalist conditions.

Acceleration↗
PubMed2002

Traumatic innominate artery transection.

Blunt innominate artery injury is a rare but often lethal complication of severe deceleration trauma. We report the case of a 38-year-old man with such an injury who was successfully operated on an emergency basis. In cases of brachiocephalic vessel trauma, a high index of suspicion in chest deceleration injuries may lead to a proper investigative process and an accurate diagnosis. Clinical signs as blood pressure gradient between the arms and widening of the mediastinum on chest X-ray is highly suggestive of trauma of the thoracic aorta and its great vessels. A chest CT scan may contribute to the diagnosis and can rule out major trauma of the aorta, but the procedure of choice for the definite diagnosis is usually the angiography. Subsequent early repair is favorable to avoid complications and fatal events. Cardiopulmonary bypass use in selected cases favors the outcome.

Accidents, Traffic↗