Rapid Changes In Direction Research Articles

Epidemiology of Foot and Ankle Injuries in NCAA Jumping Athletes in the United States During 2009-2014

Background:Foot and ankle injuries comprise a significant proportion of all injuries sustained by National Collegiate Athletic Association (NCAA) athletes. In particular, sports that combine jumping and rapid changes in direction are associated with increased lower extremity injuries.Purpose:To describe the epidemiology of foot and ankle injuries in men’s and women’s jumping sports, including NCAA men’s and women’s basketball, women’s volleyball, and women’s gymnastics, during the 2009-2010 through 2013-2014 seasons.Study Design:Descriptive epidemiology study.Methods:Injury-surveillance data were obtained from the NCAA Injury Surveillance Program for the 2009-2010 through 2013-2014 seasons. Injuries were examined by mechanism, activity during injury, and participation restriction time. Injury rates per 1000 athlete-exposures (AEs), injury rate ratios, and risk ratios with 95% CIs were calculated. Reported sex differences were calculated for men’s and women’s basketball. All 95% CIs not containing 1.0 were considered statistically significant.Results:A total of 1136 players sustained foot and ankle injuries (483 male and 653 female) over 612,680 AEs. These injuries resulted in a combined rate of 1.85 per 1000 AEs (95% CI, 1.75-1.97). Ankle sprains were the most common injury (63.7%), with lateral ligamentous complex injuries making up 77.1% of all ankle sprains. The most common foot injury varied based on sport and sex. Ankle injury rates were higher in male versus female basketball players (injury rate ratio, 1.33 [95% CI, 1.13-1.57]), but foot injury rates did not differ. Among basketball and volleyball players, player contact during jumping was the most common injury mechanism. Female gymnasts had higher overuse injury rates than other athletes (0.49/1000 AEs [95% CI, 0.30-0.74]; P < .002). Overall, female basketball players were 1.81 times more likely to sustain an overuse injury than male basketball players (95% CI, 1.02-3.20; P = .02).Conclusion:The most common foot and ankle injury sustained in collegiate jumping sports was a lateral ligamentous complex ankle sprain. Injury-prevention programs focusing on ankle flexibility, strength, and proprioception may help to alleviate the injury burden and lessen severity. Improving the anticipation of contact during jumping and landing may reduce injury rates and increase player safety. The increased prevalence of overuse injuries in female collegiate athletes competing in jumping sports necessitates further investigation to reduce injury rates through prevention and training programs.

항공기 복행사례를 통한 제주국제공항 저층 윈드시어의 특징 연구

Low level wind shear, which often occurs at Jeju International Airport, is a phenomenon that occurs when the topological location and topographical characteristics of Jeju Island are combined with weather characteristics. Low level wind shears, which are caused by rapid changes in wind direction and wind speed, pose a threat to aircraft safety and also cause abnormal situations, such as aircraft go-around, diversion, and cancellation. Many meteorological studies have been conducted on weather patterns, occurrence periods and frequency of low level wind shears. However, researches related to aircraft operations are limited where here we study the similarities and differences between strong southwest winds and bidirectional tailwind type low level wind shears based on aircraft go-around cases at Jeju International Airport. The results are expected to be used to enhance safety when operating to Jeju International Airport, which includes pilot training that reflects the characteristics generated by wind changes, pilot prior notification, providing pilots with latest trends, and increasing extra fuel.

Численное моделирование сгонно-нагонных колебаний в заливе Донузлав (Черное море)

Surge oscillations in the coastal zone of the seas can have a significant impact on the infrastructure and safety of navigation in bays and bays. The purpose of this work is to study the surge oscillations in the Donuzlav Bay located on the western coast of the Crimean Peninsula and connected to the sea by a narrow strait. The Advanced Circulation Model for Shelves Coasts and Estuaries (ADCIRC) is used for this. The numerical algorithm of the model is based on the finite element method using triangular elements and linear basis functions. The input data of the ADCIRC model were the surface wind velocity and atmospheric pressure fields over the Black Sea. Numerical modeling was performed on two nested unstructured grids. The first grid included the entire Black Sea, the second grid included the bay and the adjacent sea area. To graphically display the simulation results, the Generic Mapping Tools (GMT) mapping package was used. Analysis of the simulation results for different wind directions showed that when the wind acts on the water area of the Donuzlav Bay, seiche-like oscillations occur in the fields of sea level and currents. The intensity of these fluctuations is determined by how quickly the wind speed reaches its maximum value. Owing to the narrowness of the strait outside the bay, fluctuations do not appear. Modeling of an extreme storm situation that occurred in the Black Sea on November 11, 2007 was carried out. During the storm, a rapid change in wind direction from southeast to west occurred with a simultaneous increase in wind speed to 15–21 m/s. This caused a rise in sea level at the top of the bay to 0.5 m and an increase in the current velocity in the strait to 0.6 m/s.

Vertical and horizontal movements of bigeye tuna (Thunnus obesus) in southeastern Taiwan

ABSTRACT To learn about the movement patterns of bigeye tuna in eastern Taiwan, pop-up satellite archival tags were attached on five tuna ~55 kg and prematurely detached and popped-up after 32 to 132 days-at-liberty. Two tags were physically recovered and provided fine-scale data archiving the full 47 and 132 days-at-liberty. The deepest descent recorded was 1,292 m and the coldest temperature visited 2.7°C. During daytime, the fish spent the majority of time above 400 m at temperatures from ~10 - 25°C and at nighttime; residency was largely confined to the mixed-layer from the surface to ~100 m. Vertical movements traversing through the thermocline during the daytime are based on physiological constraints and/or rapid directional changes conducive for optimal search strategies that increases the chances of prey encounters. Bigeye tuna appear to follow the diel vertical movements of prey organisms comprising the deep sound scattering layer to exploit them as a resource.

Automatic Classification of Locomotion in Sport: A Case Study from Elite Netball.

Abstract In team sport Human Activity Recognition (HAR) using inertial measurement units (IMUs) has been limited to athletes performing a set routine in a controlled environment, or identifying a high intensity event within periods of relatively low work load. The purpose of this study was to automatically classify locomotion in an elite sports match where subjects perform rapid changes in movement type, direction, and intensity. Using netball as a test case, six athletes wore a tri-axial accelerometer and gyroscope. Feature extraction of player acceleration and rotation rates was conducted on the time and frequency domain over a 1s sliding window. Applying several machine learning algorithms Support Vector Machines (SVM) was found to have the highest classification accuracy (92.0%, Cohen’s kappa Ƙ = 0.88). Highest accuracy was achieved using both accelerometer and gyroscope features mapped to the time and frequency domain. Time and frequency domain data sets achieved identical classification accuracy (91%). Model accuracy was greatest when excluding windows with two or more classes, however detecting the athlete transitioning between locomotion classes was successful (69%). The proposed method demonstrated HAR of locomotion is possible in elite sport, and a far more efficient process than traditional video coding methods.

Changes in the kinetics and kinematics of a reactive cut maneuver after successful athletic groin pain rehabilitation.

Athletic groin pain (AGP) is a chronic, painful condition which is prevalent in players of field sports that require rapid changes of direction. Following successful rehabilitation, systematic changes have been observed in the kinetics and kinematics of pre-planned change of direction maneuvers, providing insight into potential foci for rehabilitation monitoring and for the assessment of interventions. However, changing direction in field sports is often reactive rather than pre-planned, and it is not known whether such post-rehabilitation changes are seen in reactive maneuvers. We analyzed the stance phase kinetics and kinematics of a 90° reactive cutting maneuver in 35 AGP patients before and after a successful exercise intervention program. Following the intervention, transverse plane rotation of the pelvis toward the intended direction of travel increased, and the body center of mass was positioned more anteriorly relative to the center of pressure. Ankle dorsiflexion also increased, and participants demonstrated greater ankle plantar flexor internal moment and power during the second half of stance. These findings provide insight into mechanical variables of potential importance in AGP, as identified during a maneuver based on a common sporting task.

Mining Camera Traces to Estimate Interactions Between Healthcare Workers and Patients

Background: Simulations based on models of healthcare worker (HCW) mobility and contact patterns with patients provide a key tool for understanding spread of healthcare-acquired infections (HAIs). However, simulations suffer from lack of accurate model parameters. This research uses Microsoft Kinect cameras placed in a patient room in the medical intensive care unit (MICU) at the University of Iowa Hospitals and Clinics (UIHC) to obtain reliable distributions of HCW visit length and time spent by HCWs near a patient. These data can inform modeling efforts for understanding HAI spread. Methods: Three Kinect cameras (left, right, and door cameras) were placed in a patient room to track the human body (ie, left/right hands and head) at 30 frames per second. The results reported here are based on 7 randomly selected days from a total of 308 observation days. Each tracked body may have multiple raw segments over the 2 camera regions, which we “stitch” up by matching features (eg, direction, velocity, etc), to obtain complete trajectories. Due to camera noise, in a substantial fraction of the frames bodies display unnatural characteristics including frequent and rapid directional and velocity change. We use unsupervised learning techniques to identify such “ghost” frames and we remove from our analysis bodies that have 20% or more “ghost” frames. Results: The heat map of hand positions (Fig. 1) shows that high-frequency locations are clustered around the bed and more to the patient’s right in accordance with the general medical practice of performing patient exams from their right. HCW visit frequency per hour (mean, 6.952; SD, 2.855) has 2 peaks, 1 during morning shift and 1 during the afternoon shift, with a distinct decrease after midnight. Figure 2 shows visit length (in minutes) distribution (mean, 1.570; SD, 2.679) being dominated by “check in visits” of &lt;30 seconds. HCWs do not spend much time at touching distance from patients during short-length visits, and the fraction of time spent near the patient’s bed seems to increase with visit length up to a point. Conclusions: Using fine-grained data, this research extracts distributions of these critical parameters of HCW–patient interactions: (1) HCW visit length, (2) HCW visit frequency as a function of time of day, and (3) time spent by HCW within touching distance of patient as a function of visit length. To the best of our knowledge, we provide the first reliable estimates of these parameters.Funding: NoneDisclosures: None

Rapid geomagnetic changes inferred from Earth observations and numerical simulations

Extreme variations in the direction of Earth’s magnetic field contain important information regarding the operation of the geodynamo. Paleomagnetic studies have reported rapid directional changes reaching 1° yr−1, although the observations are controversial and their relation to physical processes in Earth’s core unknown. Here we show excellent agreement between amplitudes and latitude ranges of extreme directional changes in a suite of geodynamo simulations and a recent observational field model spanning the past 100 kyrs. Remarkably, maximum rates of directional change reach ~10° yr−1, typically during times of decreasing field strength, almost 100 times faster than current changes. Detailed analysis of the simulations and a simple analogue model indicate that extreme directional changes are associated with movement of reversed flux across the core surface. Our results demonstrate that such rapid variations are compatible with the physics of the dynamo process and suggest that future searches for rapid directional changes should focus on low latitudes.

Total extraperitoneal laparoscopic inguinal hernia repair with adductor tenotomy: a 10-year experience in the treatment of athletic pubalgia.

Athletic pubalgia, commonly referred to as a "sports hernia," is a disease process characterized by groin pain produced by physical exertion often occurring in patients whose athletic activities require them to make rapid changes in direction. The groin pain is due to the traction-countertraction relationship between the adductor muscles and the weaker abdominal muscles. Hence, a few studies have shown inguinal hernia repair with adductor tenotomy to be an effective treatment for this pathology (Brody in Hernia 21:139-147, 2016, https://doi.org/10.1007/s10029-016-1520-8 ; Rossidis et al. in Surg Endosc 29:381-386, 2015, https://doi.org/10.1007/s00464-0143679-3 ). However, these studies are small and few in quantity but have demonstrated promising results. Thus, we sought to further study this combined surgical approach as a treatment for this multifactorial disease to improve our understanding and outcomes. With IRB approval, we retrospectively reviewed the charts of all patients who underwent adductor tenotomy and inguinal hernia repair for the treatment of athletic pubalgia at Mount Sinai Medical Center, Miami Beach FL. Parameters gathered included basic demographics, past medical and surgical history, athletic activity, length of surgery, length of time between surgery and follow-up, intraoperative and postoperative complications, and time to return to athletic activities. A total of 93 patients underwent inguinal hernia repair with adductor tenotomy. These procedures were all performed by a single surgeon at two academic institutions. The average age of patients was 23.4years. Athletic activities reported by the patients were as follows: American football (n = 36), soccer (n= 18), triathlon (n = 11), track and field (n = 8), and baseball (n = 5). Less-represented activities included swimming (n = 3), tennis (n = 2), lacrosse (n = 1), golf (n = 1), and other (n = 8). Mean operative time was 72.4min. Most patients were found to return to athletic activity in 28days following a standardized physical therapy regimen (92.5%). Postoperative complications included recurrence of pain/symptoms (7.5%, n = 7), urinary retention (2.2%, n = 2), pain along the adductor magnus/brevis muscle group with more extraneous activity (1.1%, n = 1), and adductor brevis hematoma 3months following surgery and rehabilitation (1.1%, n = 1). Of the patients with recurrent pain, 2/7 reported contralateral pain. Total extraperitoneal laparoscopic inguinalhernia repair with adductor tenotomy appears to be a relatively quick and safe procedure with few postoperative complications. The majority of treated athletes are able to return to full athletic activities within 28days of operation. While a return of symptoms has been seen in some patients, it is frequently observed on the contralateral side.

Charged particle isotropization in collisionless environments: turbulent magnetic fields as a conduit for random walks

We develop a simple model for the kinematics of charged particles in regions of magnetic turbulence. We approximate the local magnetic field as smoothly varying in strength and direction, where adiabatic invariance prevails, or as presenting rapid changes in direction or ‘kinks’. Particles execute guiding centre gyromotion around a field line. However, in analogy to kinetic theory for collisional environments, when the particle undergoes a rapid change in direction by some angle $\unicode[STIX]{x1D703}$ , it would instantaneously transition to Larmor motion around the new field line. This mimics Brownian motion wherein we replace collisions with other particles by rapid transitions or ‘collisions’ with other field lines. Using standard methods drawn from Brownian motion, we follow the evolution of the parallel and perpendicular components of the velocity, namely $v_{\Vert }$ and $v_{\bot }$ , and rigorously show that kinetic energy isotropization necessarily emerges.

Dynamical self-friction: how mass loss slows you down

ABSTRACT We investigate dynamical self-friction, the process by which material that is stripped from a subhalo torques its remaining bound remnant, which causes it to lose orbital angular momentum. By running idealized simulations of a subhalo orbiting within an analytical host halo potential, we isolate the effect of self-friction from traditional dynamical friction due to the host halo. While at some points in a subhalo’s orbit the torque of the stripped material can boost the orbital angular momentum of the remnant, the net effect over the long term is orbital decay regardless of the initial orbital parameters or subhalo mass. In order to quantify the strength of self-friction, we run a suite of simulations spanning typical host-to-subhalo mass ratios and orbital parameters. We find that the time-scale for self-friction, defined as the exponential decay time of the subhalo’s orbital angular momentum, scales with mass ratio and orbital circularity similar to standard dynamical friction. The decay time due to self-friction is roughly an order of magnitude longer, suggesting that self-friction only contributes at the 10 per cent level. However, along more radial orbits, self-friction can occasionally dominate over dynamical friction close to pericentric passage, where mass stripping is intense. This is also the epoch at which the self-friction torque undergoes large and rapid changes in both magnitude and direction, indicating that self-friction is an important process to consider when modelling pericentric passages of subhaloes and their associated satellite galaxies.

Severe Weather-Induced Exchange Flows through a Narrow Tidal Channel of Calcasieu Lake Estuary

Exchange flows between estuaries and the coastal ocean are important for land-ocean interactions and ecosystem health. This study is aimed at resolving severe weather-induced exchange flows between the Calcasieu Lake Estuary and Gulf of Mexico. For that purpose, we use data from a long-term deployment of side-looking acoustic Doppler current profilers (ADCPs) and conductivity-temperature-depth sensors (CTDs) as well as flow velocity data from a boat operated survey. Regression between the transport measured from a boat mounted ADCP and the velocity data from a fixed side-looking ADCP is done to calculate a long-term transport along the Calcasieu Pass. Analyses have been done for the hydrodynamic response to 16 cold fronts passing the study area. Effects of six strongest cold fronts are discussed in more detail. Results have confirmed that the hydrodynamics is highly correlated with the frequent cold fronts. The highest correlation coefficient is r ~0.75 between the north wind and along channel transport. In general, winds from the southern quadrants push water into the estuary before each frontal passage; after the passage of the front, a rapid change of wind direction to the northern quadrants produces strong outward flows. A quasi-steady state balance between the wind stress and water level difference proposed in recent studies for different systems is further confirmed and discussed in this system. The quasi-steady state balance leads to a relatively high R2 value of greater than 0.8 between the modeled water level gradient and actual observed gradient. We have also applied a regression model, derived from the momentum balance requirement, for the subtidal exchange flow as a function of wind components and their squares which yield an R2 value greater than 0.7. With a confidence in the regression model, we further implement it for twelve years from 26 February 2007 to 10 April 2019. Four extreme events during this 12-year period of time are discussed–they include the Hurricane Ike (2008), Tropical Storm Lee (2011), a warm front, and a cold front. This hindcast of the exchange flows over multiple years can provide a useful tool for coastal management and research for estuarine channels where continuous observations of velocity are not always available.

Hurricane eyewall winds and structural response of wind turbines

Abstract. This paper describes the analysis of a wind turbine and support structure subject to simulated hurricane wind fields. The hurricane wind fields, which result from a large eddy simulation of a hurricane, exhibit features such as very high gust factors (&gt;1.7), rapid direction changes (30∘ in 30 s), and substantial veer. Wind fields including these features have not previously been used in an analysis of a wind turbine, and their effect on structural loads may be an important driver of enhanced design considerations. With a focus on blade root loads and tower base loads, the simulations show that these features of hurricane wind fields can lead to loads that are substantially in excess of those that would be predicted if wind fields with equally high mean wind speeds but without the associated direction change and veer were used in the analysis. This result, if further verified for a range of hurricane and tropical storm simulations, should provide an impetus for revisiting design standards.

USE OF NUCLEAR POWER PLANT RELEASED TRITIUM AS A GROUNDWATER TRACER

Tritium presents natural radioactive isotope which can be used as tracer in hydrology. This paper presents usage of tritium in hydrogeological research of the Zagreb aquifer, which presents country`s strategic water reserves and is protected by the Republic of Croatia. In the research area higher tritium content in surface water and groundwater is the result of releasing coolant water from the Nuclear power plant Krsko. Tritium content was measured in 13 piezometers and one pumping well, in the wider area of the Petrusevec and Kosnica well fields. It has been shown that tritium from cooling water is much more pronounced than its natural seasonal variability, and it can be very useful as a tracer. Also, results showed that the intensity and delay of responses in aquifer depend on distance from the Sava River and piezometer depth. Furthermore, results suggest that variable hydrologic conditions can generate rapid change in the groundwater flow direction and affect tritium transport through the aquifer.

A Zero Placement Algorithm for Synthesis of Flat Top Beam Pattern With Low Sidelobe Level

Flat top beam pattern synthesis is increasingly important for beamformer in high mobility scenarios due to the rapid change of Direction of Arrival (DOA). A Zero Placement for Flat Top (ZPFT) beam pattern synthesis algorithm is presented in this article. It works in Z domain directly and breaks down the total response into two portions. The first portion satisfies the beamwidth requirement with low Sidelobe Level (SLL) which is realized through algorithms like Dolph-Chebyshev algorithm. The second portion is then used to create a broadening effect. The location of the broadening zeros are derived using principles result from the broadening effect analysis of two quadratic functions. Compared to conventional Finite Impulse Response (FIR) method or iterative methods, the proposed method identifies the zeros of the array factor directly and computes the weight without iteration. Since it works in the spatial angle domain directly, the steering of the mainlobe beam could be implemented through a simple angle shift. Numerical simulation confirms the effectiveness of the algorithm. ZPFT can achieve 22dB lower SLL while maintaining the same main beam performance as compared with FIR method for an Uniform Linear Array (ULA) with 7 elements. It can achieve the same optimal performance as the iteration based global optimisation techniques like Semi-Definite Relaxation (SDR) with about 380 times less computing time in an Intel Core i7 Windows platform. ZPFT can steer the main beam easily in real time. All these make it an ideal candidate for high mobility applications where the DOA changes rapidly.

Footwear insoles with higher frictional properties enhance performance by reducing in-shoe sliding during rapid changes of direction

ABSTRACTA novel 3D motion capture analysis assessed the efficacy of insoles in maintaining the foot position on the midsole platform inside the shoe during rapid change of direction manoeuvres used in team sports. An insole (TI) with increased static (35%) and dynamic (49%) coefficient of friction compared to a regular insole (SI) was tested. Change of direction performance was faster (p < .001) and perceived to be faster (p < .001) in TI compared to SI. Participants utilised greater coefficient of friction in TI compared to SI during a complete turn, but not during a 20 degree side-cut. In-shoe foot sliding reduced across the forefoot and midfoot during the braking phase of the turn and in the rearfoot during the side-cut in TI. Greater in-shoe foot sliding occurred in the turn than the side-cut across all foot regions. Results provide guidance for athletic footwear design to help limit in-shoe foot sliding and improve change of direction performance.

Planar motion controller design for a modular mechatronic device with heading compensation

MechaCells are designed as closed, scalable and modular semi-autonomous devices that can be used alone or part of a pack. In this paper, we discuss a locomotion system that uses the reaction force produced by a rotating unbalance that moves in a spherical domain with a steering mechanism. In order to produce the precise motion capability, a multi-loop controller is developed. This controller uses a friction compensation algorithm based on the mathematical model of the locomotion system. To improve the accuracy of tracking, conventional LuGre friction estimation model is extended for rapid directional changes of the MechaCell during planar motion. The linear and rotational acceleration of the device is also included in controller calculations since it affects the locomotion force generated by the unbalanced mass. The resulting control system is validated both with simulations and experiments and the effectiveness of the extended model and the controller is verified. Our results show significant improvement when a detailed friction compensation observer is used in the controller that includes the effect of sudden steering changes for precise path following.

THE MOTOR ABILITIES OF HANDBALL PLAYERS OF DIFFERENT BIOLOGICAL MATURATION

The aim of this research was to determine the differences between the results from the tests of motor abilities carried out on a selected group of handball players in relation to their biological maturation. A total of 23 handball players, belonging to a selected group, took part in this research. The overall sample of participants was divided into three groups based on their biological maturation. The measurements of motor abilities were carried out using the following tests: explosive power, sprint speed and rapid changes in direction. The statistical analysis included descriptive statistics, a univariate analysis of variance and the Bonferroni PostHoc test in order to determine whether a statistically significant difference could be detected between the groups on the tests of motor abilities. Based on the statistical analysis (ANOVA method), a difference was determined between the peak height velocity (PHV) groups for all the variables. The PostHoc test later determined that there were no differences for any of the variables between the PrePHV and MidPHV groups. Differences in all the variables were determined between the PrePHV and PostPHV groups. Differences between the MidPHV and PostPHV groups were determined for 7 variables, while no statistically significant difference was determined for 3 of the variables (5JT, T-test and the Slalom). The main contribution of this research is that it indicates to coaches the inevitability of being familiar with the biological maturation of their players for optimal selection, for adequate training design, and a decrease in the risk of injury.

Patient-specific Computational Hemodynamic Analysis for Interrupted Aortic Arch in an Adult: Implications for Aortic Dissection Initiation

The guideline for the treatment of interrupted aortic arch (IAA) in adults has not been established although most centers tend to propose surgery. There is no clear evidence for the preferred selection of surgical repair versus conservatively medical treatment for the uncertain effects of both treatments. However, reports of sporadic aortic dissection (AD) of descending aorta (DAo) in IAA in adults before surgery drew our attention. It is quite perplexing because there seems to be no risk factors for the development of AD at DAo such as long-term uncontrolled hypertension, atherosclerosis, aortic aneurysm or genetic disorder. In this paper, we carried out the numerical investigation on the hemodynamics in a patient-specific IAA model, which was reconstructed from computed tomography images. Hemodynamic parameters including the flow pattern, pressure distribution, and wall shear stress (WSS) indicators were obtained. The simulation revealed that the jet flows from the collateral arteries (CAs) induced risk hemodynamic forces on the lumen wall including high time-averaged wall shear stress (TAWSS), high pressure and rapid change of WSS direction throughout the cardiac cycle. Moreover, it is found that only a jet flow which circumferentially washes out the aortic wall might cause tears on the wall. It is concluded that the specific geometrical features of the extensive major CAs might result in the risky hemodynamics leading to the initiation and development of AD in this particular IAA patient. CFD analysis in IAA can provide a clinical reference, and the results should be further studied in depth in the future.

Shape from shading under inconsistent illumination.

People are able to perceive the 3D shape of illuminated surfaces using image shading cues. Theories about how we accomplish this often assume that the human visual system estimates a single lighting direction and interprets shading cues in accord with that estimate. In natural scenes, however, lighting can be much more complex than this, with multiple nearby light sources. Here we show that the human visual system can successfully judge 3D surface shape even when the lighting direction varies from place to place over a surface, provided the scale at which these lighting changes occur is similar to, or larger than, the size of the shape features being judged. Furthermore, we show that despite being able to accommodate rapid changes in lighting direction when judging shape, observers are generally unable to detect these changes. We conclude that, rather than relying on a single estimated illumination direction, the human visual system can accommodate illumination that varies substantially and rapidly across a surface.