Anat Meir

Drivers’ perception of vulnerable road users: A hazard perception approach

The present study examined how experienced and young-inexperienced drivers (either trained in hazard perception or not) respond to and identify pedestrians when they appear in residential roads within populated neighborhoods and in urban roads located outside neighborhoods and usually less populated. As part of a hazard perception test, participants were connected to an eye tracking system and were asked to observe 58 traffic scene movies and press a response button each time they detected a hazardous situation. Analyzing all pedestrian-related events revealed that, regardless of driving experience or training, drivers detect pedestrians less often when they appear in urban areas and more often when they appear in residential areas. Moreover, experienced drivers processed information more efficiently than young-inexperienced drivers (both trained and untrained) when pedestrians were identified. Visual search patterns in urban and residential traffic environments are discussed.

Formation and Evaluation of Act and Anticipate Hazard Perception Training (AAHPT) Intervention for Young Novice Drivers

Objective: Young novice drivers’ poor hazard perception (HP) skills are a prominent cause for their overinvolvement in traffic crashes. HP, the ability to read the road and anticipate forthcoming events, is receptive to training. This study explored the formation and evaluation of a new HP training intervention—the Act and Anticipate Hazard Perception Training (AAHPT), which is based upon exposing young novice drivers to a vast array of actual traffic hazards, aiming to enhance their ability to anticipate potential hazards during testing. Method: Forty young novices underwent one of 3 AAHPT intervention modes (active, instructional, or hybrid) or a control group. Active members observed video-based traffic scenes and were asked to press a response button each time they detected a hazard. Instructional members underwent a tutorial that included both written material and video-based examples regarding HP. Hybrid members received a condensed theoretical component followed by a succinct active component. Control was presented with a road safety tutorial. Approximately one week later, participants performed a hazard perception test (HPT), during which they observed other movies and pressed a response button each time they detected a hazard. Twenty-one experienced drivers also performed the HPT and served as a gold standard for comparison. Results: Overall, the active and hybrid modes were more aware of potential hazards relative to the control. Conclusions: Inclusion of an active–practical component generates an effective intervention. Using several evaluation measurements aids performance assessment process. Advantages of each of the training methodologies are discussed. Supplemental materials are available for this article. Go to the publishers online edition of Traffic Injury Prevention to view the supplemental file.

Effect of Distinct Lifestyle Interventions on Mobilization of Fat Storage Pools: CENTRAL Magnetic Resonance Imaging Randomized Controlled Trial

Background: We aimed to assess whether distinct lifestyle strategies can differentially affect specific body adipose depots. Methods: We performed an 18-month randomized controlled trial among 278 sedentary adults with abdominal obesity (75%) or dyslipidemia in an isolated workplace with a monitored provided lunch. Participants were randomized to isocaloric low-fat or Mediterranean/low-carbohydrate (MED/LC) diet+28 g walnuts/day with/without added moderate physical activity (PA; 80% aerobic; supervised/free gym membership). Overall primary outcome was body fat redistribution, and the main specific end point was visceral adipose tissue (VAT). We further followed the dynamics of different fat depots (deep and superficial subcutaneous, liver, pericardial, muscle, pancreas, and renal sinus) by magnetic resonance imaging. Results: Of 278 participants (age, 48 years, 89% men, body mass index, 30.8 kg/m2), 86% completed the trial with good adherence. The low-fat group preferentially decreased reported fat intake (−21.0% versus −11.5% for the MED/LC; P<0.001), and the MED/LC group decreased reported carbohydrates intake (−39.5% versus −21.3% for the low-fat group; P<0.001). The PA+ groups significantly increased the metabolic equivalents per week versus the PA− groups (19.0 versus 2.1; P=0.009). Whereas final moderate weight loss was indifferent, exercise attenuated the waist circumference rebound with the greatest effect in the MED/LCPA+ group (P<0.05). VAT (−22%), intrahepatic (−29%), and intrapericardial (−11%) fats declines were higher than pancreatic and femur intermuscular fats (1% to 2%) loss. Independent of weight loss, PA+ with either diet had a significantly greater effect on decreasing VAT (mean of difference, −6.67cm2; 95% confidence interval, −14.8 to −0.45) compared with PA−. The MED/LC diet was superior to the low-fat diet in decreasing intrahepatic, intrapericardial, and pancreatic fats (P<0.05 for all). In contrast, renal sinus and femoral intermuscular fats were not differentially altered by lifestyle interventions but by weight loss per se. In multivariate models further adjusted for weight loss, losing VAT or intrahepatic fat was independently associated with improved lipid profile, losing deep subcutaneous adipose tissue with improved insulin sensitivity, and losing superficial subcutaneous adipose tissue remained neutral except for an association with decreased leptin. Conclusions: Moderate weight loss alone inadequately reflects the significant lifestyle effects on atherogenic and diabetogenic fat depots. The MED/LC diet mobilizes specific ectopic fat depots, and exercise has an independent contribution to VAT loss. Fat depots exhibit diverse responsiveness and are differentially related to cardiometabolic markers. Distinct lifestyle protocols may uniquely induce fat mobilization from specific anatomic sites. Clinical Trial Registration: URL: https://www.clinicaltrials.gov. Unique identifier: NCT01530724.

Intermuscular adipose tissue and thigh muscle area dynamics during an 18-month randomized weight loss trial

It remains unclear whether intermuscular adipose tissue (IMAT) has any metabolic influence or whether it is merely a marker of abnormalities, as well as what are the effects of specific lifestyle strategies for weight loss on the dynamics of both IMAT and thigh muscle area (TMA). We followed the trajectory of IMAT and TMA during 18-mo lifestyle intervention among 278 sedentary participants with abdominal obesity, using magnetic resonance imaging. We measured the resting metabolic rate (RMR) by an indirect calorimeter. Among 273 eligible participants (47.8 ± 9.3 yr of age), the mean IMAT was 9.6 ± 4.6 cm(2) Baseline IMAT levels were directly correlated with waist circumference, abdominal subdepots, C-reactive protein, and leptin and inversely correlated with baseline TMA and creatinine (P < 0.05 for all). After 18 mo (86.3% adherence), both IMAT (-1.6%) and TMA (-3.3%) significantly decreased (P < 0.01 vs. baseline). The changes in both IMAT and TMA were similar across the lifestyle intervention groups and directly corresponded with moderate weight loss (P < 0.001). IMAT change did not remain independently associated with decreased abdominal subdepots or improved cardiometabolic parameters after adjustments for age, sex, and 18-mo weight loss. In similar models, 18-mo TMA loss remained associated with decreased RMR, decreased activity, and with increased fasting glucose levels and IMAT (P < 0.05 for all). Unlike other fat depots, IMAT may not represent a unique or specific adipose tissue, instead largely reflecting body weight change per se. Moderate weight loss induced a significant decrease in thigh muscle area, suggesting the importance of resistance training to accompany weight loss programs.

Intrahepatic fat, abdominal adipose tissues, and metabolic state: magnetic resonance imaging study

Intrahepatic fat (IHF) is best known to associate with waist circumference (WC) and visceral adipose tissue (VAT), but its relation to abdominal subcutaneous adipose tissue is controversial. While IHF ≥ 5% dichotomously defines fatty liver, %IHF is rarely considered as a continuous variable that includes the normal range. In this study, we aimed to evaluate %IHF association with abdominal fat subdepots, pancreatic, and renal‐sinus fats.

Intramyocellular triacylglycerol accumulation across weight loss strategies; Sub-study of the CENTRAL trial

Background Intramyocellular triacylglycerol (IMTG) is utilized as metabolic fuel during exercise and is linked to insulin resistance, but the long-term effect of weight loss strategies on IMTG among participants with abdominal fat, remain unclear. Methods In an 18-month trial, sedentary participants with abdominal fat/dyslipidemia were randomized to either a low-fat (LF) or Mediterranean/low-carbohydrate (MED/LC) diet (including 28g·day-1 of walnuts). After 6-months, the participants were re-randomized to moderate intense physical activity (PA+) or non-physical activity (PA-). Magnetic resonance imaging (MRI) was used to quantify changes of IMTG, abdominal sub-depots, hepatic and intermuscular fats. Results Across the 277 participants [86% men, age = 48 years, body-mass-index (BMI) = 31kg/m2, visceral fat = 33%] 86% completed the 18-m trial. At baseline, women had higher IMTG than men (3.4% vs. 2.3%, p<0.001) and increased IMTG was associated with aging and higher BMI, visceral and intermuscular fats, HbA1c%, HDL-c and leptin(p<0.05), but not with intra-hepatic fat. After 18 month of intervention and a -3 kg mean weight loss, participants significantly increased IMTG by 25%, with a distinct effect in the MED/LCPA+ group as compared to the other intervention groups (57% vs. 9.5–18.5%, p<0.05). Changes in IMTG were associated with visceral and intermuscular fat, metabolic syndrome, insulin and leptin (p<0.05 for all), however, these associations did not remain after adjustment for visceral fat changes. Conclusions Lifestyle strategies differentially affect IMTG accumulation; combination of exercise with decreased carbohydrate/increased unsaturated fat proportion intake greatly increase IMTG. Our findings suggest that increased IMTG during diet-induced moderate weight loss may not be directly related to cardiometabolic risk. Trial registration ClinicalTrials.gov NCT01530724

The Effect of Hazard Perception Training on Traffic-Scene Movies Categorization

Recently we have developed an innovative hazard perception training methodology, the Act and Anticipate Hazard Perception Training (AAHPT) that exposes young-inexperienced drivers to a large variety of traffic-scene movies. Trainees are asked to act (i.e., respond) each time they perceive a hazard. Trained and untrained young-inexperienced drivers, as well as experienced drivers were tested on 58 short video clips of hazardous situations and were asked to respond each time they detected a hazard. Finally, all drivers observed six traffic-scene movies and were asked to categorize them according to the similarity in their hazardous situations. In general, the trained young-inexperienced drivers were more aware of potential hazards than the untrained control group. Conclusions and implications of the categorization task are discussed.