Association between socio-economic status and physical activity is mediated by social support in Brazilian students

This study evaluated whether the relationship between socioeconomic status (SES) and moderate-to-vigorous physical activity (MVPA) is mediated by social support of peers and parents. A cross-sectional study included students (n = 1182) aged 11 to 18 years who were recruited in 2014 from public schools in Fortaleza, Brazil. Participants completed a questionnaire to assess all variables. Mediation analyses were performed to determine the role of parental support and peer support on the relationship between SES and MVPA. Also, moderated-mediation analyses with estimating of conditional indirect effects were performed in order to identify whether gender is a moderator of the mediating effect. A positive and significant association between SES and MVPA was found among Brazilian students, and social support of parents and peers were significant mediators of this relationship. Conditional indirect effects showed that both parental and peer support had a significant indirect effect among boys; only parental support had a significant indirect effect among girls. These results suggest that improving social support can help reduce the impact of SES on physical activity among Brazilian adolescents.     

Acute effects of aerobic exercise performed with different volumes on strength performance and neuromuscular parameters

The aim of the present study was to investigate the acute effect of the aerobic exercise volume on maximum strength and strength-endurance performance; and possible causes of strength decrements (i.e. central and peripheral fatigue). Twenty-one moderately trained men were submitted to a maximal incremental test to determine anaerobic threshold (AnT) and maximum dynamic strength (1RM) and strength-endurance (i.e. total volume load [TV]) tests to determine their baseline strength performance. Following, subjects performed six experimental sessions: aerobic exercise sessions (continuous running at 90% AnT) with different volumes (3?km, 5?km or 7?km) followed by 1RM or strength-endurance test in the 45° leg press exercise. Maximum voluntary isometric contraction (MVIC), voluntary activation (VA) level, contractile properties, and electromyographic activity (root mean square [RMS]) of the knee extensor muscles were assessed before and after aerobic exercises and after strength tests. TV was lower after 5?km and 7?km runs than in the control condition (12% and 22%, respectively). Additionally, TV was lower after 7?km than 3?km (14%) and 5?km (12%) runs. MVIC, VA, RMS, and contractile properties were reduced after all aerobic exercise volumes (～8%, ～5%, ～11% and ～6–14%, respectively). Additionally, MVIC, VA, and contractile properties were lower after strength tests (～15%, ～6%, ～9–26%, respectively). In conclusion, strength-endurance performance is impaired when performed after aerobic exercise and the magnitude of this interference is dependent on the aerobic exercise volume; and peripheral and central fatigue indices could not explain the different TV observed.     

Collective effectiveness in the XV de France: selections and time matter

The aim of this study was to quantify the impact of selections and shared selections in the rugby union. Players’ names, positions, and number of selections were collected for all XV de France’s games (1906–2014). Every team’s percentage of renewal of workforce was calculated for backs and forwards. During the 1987–2014 period, all second row forwards (locks), halfbacks, and centres’ shared selections (number of times when two players have competed together) were recreated. The Best vs. Rest method was applied to these remodelled dyads. They were analysed and compared with surrounding teammates as well as opponents. Head coaches similarly change their workforce for upcoming matches after winning or losing (around 30%), but losing teams renew significantly more positions in their line-ups. The recreated halfbacks, locks, and centres reveal a common pattern. Whether victorious or not, the ‘renewed couples’ victory percentage will congregate towards the XV de France’s victory percentage. For all the best recreated couples, the cumulated number of selections for forwards’ is always higher than the ones part of less efficient teams: 231.3?±?80 vs. 212.9?±?91 selections for locks’ teammates (Effect sizes (ES) small, possibly positive, 54.8%). In best recreated couples, number 8’s are significantly more experienced than their counterparts in less efficient pairs (ES small, likely positive, 76.3%). The XV de France’s collective effectiveness relies on a balance between stability and workforce renewal, which allows the building of specific position interactions and builds on experimented forwards packs. Selections and shared selections are serious collective performance parameters associated with performance.     

Reliability of unipodal and bipodal counter movement jump landings in a recreational male population

Movement patterns during landing have been suggested to be related to injury risk. The purpose of this study was to determine the inter-session reliability of kinematic variables and ground reaction forces during landing in a population of male recreational athletes after a counter movement jump. Both unipodal and bipodal landings were evaluated. Furthermore, the possibility to improve landing reliability with a verbal instruction was also studied. Twenty-four male volunteers with no history of lower extremity trauma were randomly assigned to two groups (with and without verbal landing instruction). An optoelectronic 3D system and force plates were used to measure the lower limb joint angles and the ground reaction forces during landing. Intraclass correlation values show moderate to excellent inter-session reliability for the bipodal task (ICC average: 0.80, range: 0.46–0.97) and poor to excellent reliability for the unipodal task (ICC average: >0.75, range: 0.20–0.95). However, large standard errors of measurement values at the ankle joint at impact (27.6?±?11.5°) and for the vertical ground reaction forces (394?±?1091 N) show that some variables may not be usable in practice. The verbal instruction had a negative effect on the reliability of unipodal landing but improved the reliability of bipodal landing. These findings show that the reliability of a landing task is influenced by its motor complexity as well as the instruction given to the subject.     

虞山药用植物资源研究初报（二）——草本植物类

虞山药用的草本类植物约１３０种,分隶５２个科,１０８个属,通过对这些草本类药用植物在虞山上的分布状况调查及药用价值的描述,为合理开发利用提供一定的依据。     

Intensity and physiological strain of competitive ultra-endurance exercise in humans

The aim of this study was to determine the magnitude and pattern of intensity, and physiological strain, of competitive exercise performed across several days, as in adventure racing. Data were obtained from three teams of four athletes (7 males, 5 females; mean age 36 years, s = 11; cycling .VO(2 peak) 53.9 ml . kg(-1) . min(-1), s = 6.3) in an international race (2003 Southern Traverse; 96 - 116 h). Heart rates (HR) averaged 64% (95% confidence interval: +/- 4%) of heart rate range [%HRR = (HR - HR(min))/(HR(max) - HR(min)) x 100] during the first 12 h of racing, fell to 41% (+/-4%) by 24 h, and remained so thereafter. The level and pattern of heart rate were similar across teams, despite one leading and one trailing all other teams. Core temperature remained between 36.0 and 39.2 degrees C despite widely varying thermal stress. Venous samples, obtained before, during, and after the race, revealed increased neutrophil, monocyte and lymphocyte concentrations (P < 0.01), and increased plasma volume (25 +/- 10%; P < 0.01) with a stable sodium concentration. Standardized exercise tests, performed pre and post race, showed little change in the heart rate-work rate relationship (P = 0.53), but a higher perception of effort post race (P < 0.01). These results provide the first comprehensive report of physiological strain associated with adventure racing.     

Development of Pre-Service Mathematics Teachers' Professional Knowledge and Identity in Working with Information and Communication Technology

This paper describes the workundertaken in a course in communication andinformation technology in a pre-service programfor secondary school mathematics teachers. Thiscourse aimed to help pre-service teachersdevelop a positive attitude regarding ICT anduse it confidently. It focused on theexploration of educational software and of theInternet's potential as a means of research andproduction of web sites. We discuss how thepre-service mathematics teachers evaluate theirwork concerning their commitment, difficultiesthey found, learning they identified, andpersonal relationship. We also analyse theeffects of the course on the development oftheir professional knowledge and identity.