The influence of race length on arterial compliance following an ultra-endurance marathon     

Alis Bonsignore  Shannon S. D. Bredin  Holly Wollmann  Barb Morrison  Andrew Jeklin  Lauren Buschmann 《European Journal of Sport Science》2017,17(4):441-446

There is inconclusive evidence concerning the effects of routine participation in ultra-endurance events on cardiovascular disease (CVD) risk. Arterial compliance is a reliable, non-invasive, and effective tool for evaluating CVD risk. The purpose of this research was to examine if race length influences acute changes in arterial compliance following an ultra-marathon event. A total of 46 ultra-marathon runners were recruited including 21 participants (39.8?±?8.3?years, 6 females) in the 80-km event and 25 participants (43.7?±?9.8?years, 3 female) in the 195-km event. Arterial compliance was measured via radial applanation tonometry (CR-2000, HDI) for diastolic pulse contour analysis before and following the race. Significant between-group differences were found for changes in large arterial compliance with a decrease (increase in stiffness) following the 195-km event and an increase following the 80-kilometre event (p?<?.05). Longer race lengths are associated with greater reductions in large arterial compliance following recreational ultra-marathon running. Assessment of arterial compliance might be a useful prognostic tool to assess the long-term risk of CVD among ultra-marathon runners.  相似文献   

Resting MAPK expression in chronically trained endurance runners     

Justin X. Nicoll  Andrew J. Galpin  Donald B. Thomason  Christopher A. Moore 《European Journal of Sport Science》2017,17(9):1194-1202

Purpose: There is a paucity of research investigating the expression of mitogen-activated protein kinases (MAPK) in chronically trained (CT) athletes. Thus, it is unclear how MAPK may contribute to performance and muscle adaptation in CT subjects. The purpose of this study was to determine MAPK total protein, and phosphorylated expression of extracellular signal-regulated kinases 1 and 2 (ERK1/2), c-Jun N-terminal kinase (JNK), and p38-MAPK (p38) between untrained, and chronically trained runners. Methods: Tissue samples were analysed from sedentary (SED; n?=?5) controls and chronically trained runners (CT; n?=?5). Resting muscle biopsy samples were analysed for total-MAPK – and ratio of phosphorylated/total (p-MAPK) – ERK1/2, JNK, and p38-MAPK via western blotting. Mann–Whitney U tests and effect sizes were utilized to determine differences in total MAPK protein content and phosphorylation status between SED and CT subjects. Results: There was no difference in total-MAPK expression between SED and CT (p?>?.05). p-p38-MAPK tended to be greater for CT compared to SED (p?=?.07). There were moderate effect sizes of decreased pERK/total-ERK (d?=??0.69) and increased pJNK/total-JNK (d?=?0.54) in CT compared to SED. There was a positive correlation between p-p38-MAPK/total-MAPK and the percentage of type I fibres (r?=?0.73, p?=?.016). Conclusion: Contrary to previous studies, chronic endurance training does not greatly influence total MAPK protein expression in chronically trained runners. However, resting phosphorylation of p38-MAPK may contribute to enhanced oxidative metabolism at chronically trained levels. These alterations are likely involved in the different physiological adaptations that occur following long-term training or at highly competitive levels.  相似文献   

Combined individual scrummaging kinetics and muscular power predict competitive team scrum success     

Andrew Green  Chloe Dafkin  Samantha Kerr  Warrick McKinon 《European Journal of Sport Science》2017,17(8):994-1003

Scrummaging is a major component of Rugby Union gameplay. Successful scrummaging is dependent on the coordination of the forward players and the strength of the eight individuals. The study aim was to determine whether individual scrummaging kinetics and other candidate factors associated with scrummaging performance discriminate team scrum performances. Sixteen club-level forwards (stature: 1.80?±?0.1?m; mass: 99.0?±?18.2?kg) were initially divided into two scrummaging packs. A total of 10 various scrum permutations were tested, where players were randomly swapped between the two packs. Winning scrums were determined by two observers on opposite sides of the scrum. Fatigue (100?mm visual analogue scale (VAS)) and scrummaging effort (6–20 rating of perceived exertion (RPE)) were assessed following each scrum contest. Individual scrummaging kinetics were acquired through an instrumented scrum ergometer and muscular power indicated through vertical jump heights. Student’s t-tests were used to differentiate between winning and losing scrum packs. VAS and RPE were assessed using repeated measures ANOVAs. Winning scrum packs had significantly larger combined force magnitudes (p?<?.002), regardless of the player contribution calculations. Additionally, winning packs had less individual movement (p?=?.033) and higher combined vertical jump heights (p?<?.001) but were not significantly heavier (p?=?.759) than losing scrum packs. While perceived VAS and RPE values progressively increased (p?<?.001), no differences in the individual scrum magnitudes were observed between the 1st and 10th scrum (p?=?.418). The results indicated that the combination of individual forces, variation in movement and factors related to scrummaging performance, such as vertical jump height, were associated with team scrummaging success.  相似文献   

Short-term reliability of inflammatory mediators and response to exercise in the heat     

Joshua H. Guy  Andrew M. Edwards  Catherine M. Miller  Glen B. Deakin  David B. Pyne 《Journal of sports sciences》2017,35(16):1622-1628

Prospective application of serum cytokines, lipopolysaccharide (LPS), and heat shock proteins (eHSPs) requires reliable measurement of these biomarkers that can signify exercise-induced heat stress in hot conditions. To accomplish this, both short-term (7 day) reliability (at rest, n = 12) and the acute responsiveness of each biomarker to exercise in the heat (pre and post 60-min cycling, 34.5°C and 70% RH, n = 20) were evaluated. Serum was analysed for the concentration of C-reactive protein (CRP), interleukin-6 (IL-6), heat shock protein 72 (eHSP72), immunoglobulin M (IgM) and LPS. Test–retest reliability was determined as the coefficient of variation (CV). Biomarkers with the least short-term within-participant variation were IL-6 (19%, ±20%; CV, ±95% confidence limits (CL)) and LPS (23%, ±13%). Greater variability was observed for IgM, eHSP72 and CRP (CV range 28–38%). IL-6 exhibited the largest increase in response to acute exercise (95%, ±11%, P = < 0.001) and although CRP had a modest CV (12%, ±7%), it increased substantially post-exercise (P = 0.02, ES; 0.78). In contrast, eHSP72 and LPS exhibited trivial changes post-exercise. It appears variation of common inflammatory markers after exercise in the heat is not always discernible from short-term (weekly) variation.  相似文献   

Effects of false-start disqualification rules on response-times of elite-standard sprinters     

Kevin C. Brosnan  Kevin Hayes  Andrew J. Harrison 《Journal of sports sciences》2017,35(10):929-935

The 100 ms ruling for false start disqualification at athletic competitions governed by the International Association of Athletics Federations has been in force since the early 1990s. Throughout this period, there have been marked changes to the rules that govern the disqualification of athletes from sprint events incorporating starts from blocks. This study analysed all available World and European Championship response-time (RT) data from 1999 to 2014 to examine effects of rule changes on competition RT at major championships. The exponentially modified Gaussian distribution was used to model RT and make comparisons relative to athletes’ sex, ruling periods and competition rounds. Revised RT thresholds of 115 ms and 119 ms were identified for men and women, respectively, indicating that the current 100 ms rule could result in some false starts not being detected in competitive athletics. The study proposes that when using existing International Association of Athletics Federations approved systems, the false start detection threshold should be increased and that men and women athletes should have different thresholds because of substantial evidence of a sex-based difference in RT in elite-standard athletes.  相似文献   

Exposing athletes to playing form activity: outcomes of a randomised control trial among community netball teams using a game-centred approach     

Andrew Miller  Stephen Harvey  David Morley  Roland Nemes  Maggie Janes  Narelle Eather 《Journal of sports sciences》2017,35(18):1846-1857

This study evaluated whether exposing junior netball players to greater amounts of competition relevant activity (playing form activity) had an effect on game play outcomes and session involvement. A group-randomised controlled trial in one junior netball club in the Hunter Region, NSW, Australia. Ninety female athletes (mean age = 9.04 years, SD 1.53) were randomised by team (n = 11) into the intervention (n = 41) or 9-week wait-list control (n = 49) condition. The Professional Learning for Understanding Games Education into Sport (PLUNGE into Sport) programme was undertaken in the first half of nine training sessions (9 × 30 min). The intervention exposed athletes to playing form activity through a coach development programme within training sessions. Athletes’ decision-making, support and skill outcomes during a small-sided invasion game, and session involvement (pedometer step/min), were measured at baseline and 9-week follow-up. Linear mixed models revealed significant group-by-time intervention effects (P < 0.05) for decision-making (d = 0.4) and support (d = 0.5) during game play, and in-session activity (d = 1.2). An intervention exposing athletes to greater levels of playing form activity, delivered via a coach education programme, was efficacious in improving athlete decision-making and support skills in game play and increasing athlete involvement during sessions.  相似文献   

Identification of temporal factors related to shot performance for indoor recurve archery     

Andrew J. Callaway  Johanna Wiedlack  Mario Heller 《Journal of sports sciences》2017,35(12):1142-1147

The purpose of this study was to investigate the temporal phases of the archery shot cycle that distinguish the arrows distance from centre, in an attempt to understand critical factors that affect performance. Fifteen archers of varying ability each performed 30 shots at 18 m. Fourteen potential predictor variables were measured for statistical modelling by stepwise multiple linear regression. The results show that pre-shot time (pre-performance routine), follow-through time (post-performance routine), aiming time, speed of the arrow and the %variation in clicker-release time, account for 7.7% of the variation in predicting shot performance. The results have implications for practice demonstrating factors that coaches should focus on to develop their athletes. Further work on pre-, but more importantly, post-performance routines are needed generally within sport research as they are lacking and have been shown to be important contributing factors in a number of sports.  相似文献   

Pernicious nonsense ‘Moonfleet’ by J. Meade Falkner     

Andrew Stibbs 《Children‘s Literature in Education》1970,1(3):11-20

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Copper wire rope lightning conductors     

Andrew Smith 《Journal of The Franklin Institute》1847,43(6):426-427

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The impulse strength of solid and gas-filled high voltage cables     

Andrew Gemant 《Journal of The Franklin Institute》1942,234(6):519-533

A method is presented that allows the computation of the impulse strength of insulating oil and of solid and gas-filled cables. The principle of the calculation is that breakdown is initiated by currents due to an electronic emission from the cathode; in gas-filled cables these currents are increased by means of gaseous ionization in the butt spaces. Approximate equations are deduced and numerical impulse strength values for insulating oil and solid cable computed, resulting in fair agreement with experimental observations. Extending the equations to gas-filled cables, numerical impulse data for varying gas pressure and for varying radial butt-space alignment are evaluated.  相似文献