Recent advances in intergroup contact theory

Recent advances in intergroup contact theory and research are reviewed. A meta-analysis with 515 studies and more than 250,000 subjects demonstrates that intergroup contact typically reduces prejudice (mean r = −.21). Allport's original conditions for optimal contact - equal status, common goals, no intergroup competition, and authority sanction - facilitate the effect but are not necessary conditions. There are other positive outcomes of intergroup contact, such as greater trust and forgiveness for past transgressions. These contact effects occur not only for ethnic groups but also for such other groups as homosexuals, the disabled and the mentally ill. Intergroup friendship is especially important. Moreover, these effects typically generalize beyond the immediate outgroup members in the situation to the whole outgroup, other situations, and even to other outgroups not involved in the contact. They also appear to be universal - across nations, genders, and age groups. The major mediators of the effect are basically affective: reduced anxiety and empathy. And even indirect contact reduces prejudice - vicarious contact through the mass media and having a friend who has an outgroup friend. Of course, negative contact occurs - especially when it is non-voluntary and threatening. Criticisms of the theory and policy implications are also discussed.     

Classification of trampoline jumps using inertial sensors

The automatic segmentation and classification of an unknown motion data stream according to given motion categories constitute an important research problem with applications in computer animation, medicine and sports sciences. In this paper, the scenario of trampoline motions is considered, where an athlete performs a routine consisting of sequence of jumps that belong to predefined motion categories such as pike jumps or somersaults. As main contribution, a fully automated approach for capturing, segmenting, and classifying trampoline routines according to these categories is introduced. Since trampoline motions are highly dynamic and spacious, optical motion capturing is problematic. Instead, it is reverted to a small number of inertial sensors attached to the athlete’s body. To cope with measurement noise and performance differences, suitable feature and class representations are introduced that are robust to spatial and temporal variations while capturing the characteristics of each motion category. The experiments show that the approach reliably classifies trampoline jumps across different athletes even in the presence of significant style variations.     

Kinematical analysis of the V2 ski skating technique: A longitudinal study

To characterise timing of movements and evaluate performance effects of technique alterations in V2 ski skating, 13 elite male cross-country skiers (age, 23 ± 2 years; stature, 182 ± 6 cm; body mass, 76 ± 8 kg; V2 V?O_2max, 79.3 ± 4.4 mL · kg^?1 · min^?1) were tested four times during the preparation and competition phase on a roller ski treadmill. Each test consisted of submaximal intensities of exercise for determination of oxygen cost followed by one 1000-m performance test. Hip movement (from accelerometer data) and joint angles (2D video) were determined for high-intensity exercise (6° and 3.5 m · s^?1; ~ 97–100% of V?O_2peak). Each ski thrust consisted of three phases: gliding phase (18–50% of cycle time), poling phase (50–70% of cycle time), and kick phase (70–78% of cycle time). Flexion/extension of the hip initiated all phases, followed by the respective joints in legs and arms. Mixed-model analysis, adjusting for systematic time-point effects, identified that both reduced vertical hip acceleration and increased cycle time gave a small likely reduction in oxygen cost and 1000-m time. In conclusion, well-developed hip movement is a key characteristic of the V2 technique for elite-standard skiers’ long-term performance development.     

Associations between prolonged sedentary time and breaks in sedentary time with cardiometabolic risk in 10–14-year-old children: The HAPPY study

This study examines the association between prolonged sedentary time and breaks in sedentary time with cardiometabolic risk in 10–14-year-old children. This cross-sectional design study analysed accelerometry-determined sedentary behaviour and physical activity collected over 7 days from 111 (66 girls) UK schoolchildren. Objective outcome measures included waist circumference, fasting lipids, fasting glucose, blood pressure, and cardiorespiratory fitness. Logistic regression was used for the main data analysis. After adjustment for confounders, the odds of having hypertriglyceridaemia (P = 0.03) and an increased clustered cardiometabolic risk score (P = 0.05) were significantly higher in children who engaged in more prolonged sedentary bouts per day. The number of breaks in sedentary time per day was not associated with any cardiometabolic risk factor, but longer mean duration of daily breaks in sedentary time were associated with a lower odds of having abdominal adiposity (P = 0.04) and elevated diastolic blood pressure (P = 0.01). These associations may be mediated by engagement in light activity. This study provides evidence that avoiding periods of prolonged uninterrupted sedentary time may be important for reducing cardiometabolic disease risk in children.     

Extracurricular Physical Activity Programs in California Private Secondary Schools

Purpose: Interscholastic, intramural, and club physical activity (PA) programs can be important contributors to student PA accrual at schools. Few studies have assessed factors related to the provision of these extracurricular PA programs, especially in private schools. Methods: We used a 16-item questionnaire to assess the associations and influences of selected factors relative to extracurricular PA program policies and practices in 450 private California secondary schools. Associations were evaluated using contingency table analyses (i.e., chi-squared, effect size, and post-hoc analyses). Results: Six factors were associated with schools providing extracurricular PA programs: school location, level, enrollment, and religious classification and whether the physical education (PE) program met state PE time standards and was taught by PE specialists. Conclusions: Both static factors (e.g., school location, level, enrollment, and religious affiliation) and modifiable factors (e.g., meeting PE standards and employing specialists) affect the provision of extracurricular PA programs. As education is state-mandated, additional study is recommended to assess the generalizability of these findings to other states and to public schools.     

The effect of mountain bike wheel size on cross-country performance

ABSTRACT

The purpose of this study was to determine the influence of different wheel size diameters on indicators of cross-country mountain bike time trial performance. Nine competitive male mountain bikers (age 34.7 ± 10.7 years; stature 177.7 ± 5.6 cm; body mass 73.2 ± 8.6 kg) performed 1 lap of a 3.48 km mountain bike (MTB) course as fast as possible on 26″, 27.5″ and 29″ wheeled MTB. Time (s), mean power (W), cadence (revs · min^?1) and velocity (km · h^?1) were recorded for the whole lap and during ascent and descent sections. One-way repeated measure ANOVA was used to determine significant differences. Results revealed no significant main effects for any variables by wheel size during all trials, with the exception of cadence during the descent (F_{(2, 16)} = 8.96; P = .002; P² = .53). Post hoc comparisons revealed differences lay between the 26″ and 29″ wheels (P = .02). The findings indicate that wheel size does not significantly influence performance during cross-country when ridden by trained mountain bikers, and that wheel choice is likely due to personal choice or sponsorship commitments.     

Studies of Physical Education in the United States Using SOFIT: A Review

Purpose: An objective database for physical education (PE) is important for policy and practice decisions, and the System for Observing Fitness Instruction Time (SOFIT) has been identified as an appropriate surveillance tool for PE across the nation. The purpose of this review was to assess peer-reviewed studies using SOFIT to study K–12 PE in U.S. schools. Method: The Preferred Reporting Items for Systematic Reviews and Meta-Analyses informed the review, and 10 databases were searched for English-language articles published through 2016. A total of 704 records identifying SOFIT were located, and 137 full texts were read. Two authors reviewed full-text articles, and a data extraction tool was developed to select studies and main topics for synthesis. Results: Twenty-nine studies that included direct observations of 12,256 PE lessons met inclusion criteria; 17 were conducted in elementary schools, 9 in secondary schools, and 3 in combined-level schools. Inconsistent reporting among studies was evident, including not all identifying the number of classes and teachers involved. All studies reported student physical activity, but fewer reported observer reliabilities (88%), lesson context (76%), teacher behavior (38%), and PE dosage (34%). The most frequently analyzed independent variables were teacher preparation (48%), lesson location (38%), and student gender (31%). Conclusions: SOFIT can be used reliably in diverse settings. Inconsistent reporting about study procedures and variables analyzed, however, limited comparisons among studies. Adherence to an established protocol and more consistent reporting would more fully enable the development of a viable database for PE in U.S. schools.