High frequency periodic forcing of the oscillatory catalytic CO oxidation on Pt(110)

Resonant periodic forcing is applied to catalytic CO oxidation on platinum (110) in the oscillatory regime. The external parameters are chosen such that the unperturbed system spontaneously develops chemical turbulence. By periodically modulating the CO partial pressure, changes in the spatiotemporal behaviour of the system can be induced: the turbulent behaviour is suppressed and frequency locked patterns with sub-harmonic entrainment develop. A novel gas-driving compressor has been implemented to perform the experimental work

An investigation into the use of a movement assessment protocol for under 14 rugby league players in a talent development environment

This study investigated the use of a movement assessment protocol for under-14 rugby league players by evaluating the relationships between chronological age, maturation, and anthropometry, and fitness and qualitative movement assessments (QMA) of 84 rugby league players within a talent development environment. A one-way ANOVA showed Quartile 1 players were more mature, taller (173.0±7.4 vs 165.0±8.0 cm) and heavier (72.5 vs 58.7 kg) than Quartile 4 players, with no difference evident for fitness or QMA measures. Earlier maturing players had significantly greater upper body power (5.39±0.46 vs 4.42±0.68 m), 20m speed (3.48±0.14 vs 3.65±0.19s) and power pass QMA (13.88±2.18 vs 12.00±1.98) than later maturing players. Body mass was positively related to power pass fitness (r=0.50) and QMA (r=0.22) scores, with negative relationships found for vertical jump performance (r=-0.24), sprint QMA (r=-.29) and turn off either foot QMA (r=-0.26). There is a need to educate coaches about the use of both fitness testing and qualitative movement assessments to identify talented U14 rugby league players, which potentially reduces relative age and maturational biases

Lower limb stiffness and maximal sprint speed in 11-16-year-old boys

The purpose of the study was to examine the relationship between vertical stiffness, leg stiffness and maximal sprint speed in a large cohort of 11-16-year-old boys. Three-hundred and thirty-six boys undertook a 30 m sprint test using a floor-level optical measurement system, positioned in the final 15 m section. Measures of speed, step length, step frequency, contact time and flight time were directly measured whilst force, displacement, vertical stiffness and leg stiffness, were modeled from contact and flight times, from the two fastest consecutive steps for each participant over two trials. All force, displacement and stiffness variables were significantly correlated with maximal sprint speed (p 0.7) relationship with sprint speed, while vertical center of mass displacement, absolute vertical stiffness, relative peak force, and maximal leg spring displacement had large (r > 0.5) relationships. Relative vertical stiffness and relative peak force did not significantly change with advancing age (p > 0.05), but together with maximal leg spring displacement accounted for 96% of the variance in maximal speed. It appears that relative vertical stiffness and relative peak force are important determinants of sprint speed in boys aged 11-16 years, but are qualities that may need to be trained due to no apparent increases from natural development. Practitioners may wish to utilize training modalities such as plyometrics and resistance training to enable adaptation to these qualities due to their importance as predictors of speed in youth

High-Intensity Interval Training Interventions in Children and Adolescents: A Systematic Review

BackgroundWhilst there is increasing interest in the efficacy of high-intensity interval training in children and adolescents as a time-effective method of eliciting health benefits, there remains little consensus within the literature regarding the most effective means for delivering a high-intensity interval training intervention. Given the global health issues surrounding childhood obesity and associated health implications, the identification of effective intervention strategies is imperative.ObjectivesThe aim of this review was to examine high-intensity interval training as a means of influencing key health parameters and to elucidate the most effective high-intensity interval training protocol.MethodsStudies were included if they: (1) studied healthy children and/or adolescents (aged 5–18 years); (2) prescribed an intervention that was deemed high intensity; and (3) reported health-related outcome measures.ResultsA total of 2092 studies were initially retrieved from four databases. Studies that were deemed to meet the criteria were downloaded in their entirety and independently assessed for relevance by two authors using the pre-determined criteria. From this, 13 studies were deemed suitable. This review found that high-intensity interval training in children and adolescents is a time-effective method of improving cardiovascular disease biomarkers, but evidence regarding other health-related measures is more equivocal. Running-based sessions, at an intensity of >90% heart rate maximum/100–130% maximal aerobic velocity, two to three times a week and with a minimum intervention duration of 7 weeks, elicit the greatest improvements in participant health.ConclusionWhile high-intensity interval training improves cardiovascular disease biomarkers, and the evidence supports the effectiveness of running-based sessions, as outlined above, further recommendations as to optimal exercise duration and rest intervals remain ambiguous owing to the paucity of literature and the methodological limitations of studies presently available

Influence of training status and exercise modality on pulmonary O2 uptake kinetics in pre-pubertal girls

The limited available evidence suggests that endurance training does not influence the pulmonary oxygen uptake (V(O)(2)) kinetics of pre-pubertal children. We hypothesised that, in young trained swimmers, training status-related adaptations in the V(O)(2) and heart rate (HR) kinetics would be more evident during upper body (arm cranking) than during leg cycling exercise. Eight swim-trained (T; 11.4 +/- 0.7 years) and eight untrained (UT; 11.5 +/- 0.6 years) girls completed repeated bouts of constant work rate cycling and upper body exercise at 40% of the difference between the gas exchange threshold and peak V(O)(2). The phase II V(O)(2) time constant was significantly shorter in the trained girls during upper body exercise (T: 25 +/- 3 vs. UT: 37 +/- 6 s; P < 0.01), but no training status effect was evident in the cycle response (T: 25 +/- 5 vs. UT: 25 +/- 7 s). The V(O)(2) slow component amplitude was not affected by training status or exercise modality. The time constant of the HR response was significantly faster in trained girls during both cycle (T: 31 +/- 11 vs. UT: 47 +/- 9 s; P < 0.01) and upper body (T: 33 +/- 8 vs. UT: 43 +/- 4 s; P < 0.01) exercise. The time constants of the phase II V(O)(2)and HR response were not correlated regardless of training status or exercise modality. This study demonstrates for the first time that swim-training status influences upper body V(O)(2) kinetics in pre-pubertal children, but that cycle ergometry responses are insensitive to such differences

Anthropometric and Physical Qualities of Elite Male Youth Rugby League Players

Rugby league is a collision team sport played at junior and senior levels worldwide, whereby players require highly developed anthropometric and physical qualities (i.e., speed, change of direction speed, aerobic capacity, muscular strength and power). Within junior levels, professional clubs and national governing bodies implement talent identification and development programmes to support the development of youth (i.e., 13-20 years) rugby league players into professional athletes. This review presents and critically appraises the anthropometric and physical qualities of elite male youth rugby league players aged between 13 and 20 years by age category, playing standard and playing position. Height, body mass, body composition, linear speed, change of direction speed, aerobic capacity, muscular strength and power characteristics are presented and demonstrate that qualities develop with age and differentiate between playing standard and playing position. This highlights the importance of anthropometric and physical qualities for the identification and development of youth rugby league players. However, factors such as maturity status, variability in development, longitudinal monitoring and career attainment should be considered to help understand, identify and develop the physical qualities of youth players. Further extensive research is required into the anthropometric and physical qualities of youth rugby league players, specifically considering national standardized testing batteries, links between physical qualities and match performance, together with intervention studies, to inform the physical development of youth rugby league players for talent identification and development purposes