The acute effects of vibration stimulus following FIFA 11+ on agility and reactive strength in collegiate soccer players

Purpose： The aim of this study was to assess the effects of combining the FIFA 11＋ and acute vibration training on reactive strength index （RSI） and 505 agility. Methods： Seventy-four male collegiate soccer players took part in the study and were randomly assigned to FIFA 11＋ with acute vibration group （FIFA ＋ WBV）, FIFA 11＋ with isometric squat group （FIFA ＋ IS） or a control group consisting of the F1FA 11＋ alone （Con）. The warm-up consisted of the FIFA 11＋ and was administered to all participants. The participants in the acute vibration group were exposed to 30 s whole body vibration in squat position immediately post warm-up. The isometric group completed an isometric squat for 30 s immediately post warm-up. Results： RSI significantly improved pre- to post-intervention amongst FIFA ＋ WBV （p 〈 0.001） due to a decrease in contact time （p 〈 0.001） in comparison to FIFA ＋ IS and Con, but 505 agility was not affected. Conclusion： The results of this study suggest the inclusion of an acute bout of WBV post FIFA 11＋ warm-up produces a neuromuscular response leading to an improvement in RSI. Future research is required to examine the exact mechanisms behind these improvements amongst other populations and over time course of the performance.

Adsorption/reaction energetics measured by microcalorimetry and correlated with reactivity on supported catalysts: A review

The formations and transformations of the chemical bonds of reactants and intermediates on cata- lyst surfaces occur in conjunction with the evolution of heat during catalytic reactions. Measure- ment of this evolved heat is helpful in terms of understanding the nature of the interactions be- tween the catalyst and the adsorbed species, and provides insights into the reactivity of the catalyst. Although various techniques have previously been applied to assessments of evolved heat, direct measurements using a Tian-Calvet microcalorimeter are currently the most reliable method for this purpose. In this review, we summarize the relationship between the adsorption/reaction energetics determined by microcalorimetry and the reactivities of supported catalysts, and examine the im- portant role of microcalorimetry in understanding catalytic performance from the energetic point of view.

Changes in balance ability,power output,and stretch-shortening cycle utilisation after two high-intensity intermittent training protocols in endurance runners

Purpose：This study aimed to describe the acute effects of 2 different high-intensity intermittent trainings（HIITs） on postural control,countermovement jump（CMJ）,squat jump（SJ）,and stretch-shortening cycle（SSC） utilisation,and to compare the changes induced by both protocols in those variables in endurance runners.Methods：Eighteen recreationally trained endurance runners participated in this study and were tested on 2 occasions：10 runs of 400 m with 90 s recovery between running bouts（10×400 m）,and 40 runs of 100 m with 30 s recovery between runs（40 × 100 m）.Heart rate was monitored during both HIITs;blood lactate accumulation and rate of perceived exertion were recorded after both protocols.Vertical jump ability（CMJ and SJ） and SSC together with postural control were also controlled during both HIITs.Results：Repeated measures analysis revealed a significan improvement in CMJ and SJ during 10 × 400 m（p〈0.05）,whilst no significan changes were observed during 40×100 m.Indexes related to SSC did not experience significan changes during any of the protocols.As for postural control,no significan changes were observed in the 40×100 m protocol,whilst significan impairments were observed during the 10×400 m protocol（p〈0.05）.Conclusion：A protocol with a higher number of shorter runs（40×100 m） induced different changes in those neuromuscular parameters than those with fewer and longer runs（10×400 m）.Whereas the 40×100 m protocol did not cause any significan changes in vertical jump ability,postural control or SSC utilisation,the 10×400 m protocol impaired postural control and caused improvements in vertical jumping tests.

Review of Matrix Aluminas for Refractory Formulations

Historically,ground calcined aluminas were the first high-alumina matrix products that were used in refractory formulations, in both shaped and unshaped products. At that time the flow properties of castables were enhanced by the use of silica fume. This was followed later by the development of fully ground reactive aluminas which contributed to the design of the matrix below 63 μm. In addition to aggregate fines,a range of bi-modal and multi-modal reactive aluminas were also developed. These not only gave improved physical properties but also better castable workability. This paper reviews matrix alumina developments over time,from basic ground calcines to complex multi-modal matrix products and their globally standardised manufacture.

Phase Specific Comparisons of High and Low Vertical Jump Performance in Collegiate Female Athletes

Introduction Countermovement vertical jump testing has become a staple in athlete assessment protocols.As the popularity of jump testing has grown,a need and interest has also grown in identifying the factors that underpin high-level outputs.As jump height alone as a variable in evaluating vertical jump performance has been questioned in athletic populations,other variables such as the reactive strength index modified(RSIm)allow for not only evaluating the outcome,but the strategy used in obtaining that outcome.Purpose Thus,the purpose of this investigation was to examine the differences in high and low vertical jump performances,as determined by the RSIm in female collegiate athletes.Methods Thirty NCAA Division I female volleyball and basketball athletes performed countermovement vertical jump trials on a force platform.The sample was then broken into two groups as determined by median RSIm values.Independent sample t-test were then used to compare groups.Results High RSIm group displayed greater jump heights(P<0.05).Additionally,the high performing group displayed lower eccentric duration times(P<0.05).No differences between groups were seen in kinetic variables.Conclusion The high performing group displayed faster eccentric times which translated to lower values in time to take-off though not statistical significant.The higher RSIm values appear to be a result of both greater jump heights and reduced time to take off.Thus,focus being placed on the speed of the movement during training would be of benefit in improving RSIm values.

Relationships Between Vertical Jump Metrics and Sprint Performance,and Qualities that Distinguish Between Faster and Slower Sprinters

Purpose This study aimed to investigate the relationships between vertical jump metrics and phases during a 60 m sprint.The variances in strength qualities between sprinters of different ability levels were also compared.Methods Eighteen young male elite sprinters(age:18.1±1.3 years;stature:1.72±0.07 m;body mass:66.3±6.2 kg)were assessed for squat(SJ),countermovement(CMJ),drop(DJ),and standing long jumps,a maximal load back-squat,and a 60-m sprint from a block-start.The relationships between sprint performances with all variables were analysed using correlation and multiple regression while discriminative parameters between fast(100 m time:~10.50 s)and slow(~11.00 s)sprint groups were assessed using independent t-tests.Results Higher associations existed between vertical jumps and longer sprint distances,especially between SJ height and relative peak power with 10 m(r=−0.47 and−0.47,respectively),30 m(−0.71 and−0.74),60 m(−0.76 and−0.81),10-30 m(−0.80 and−0.86),and 30-60 m(−0.78 and−0.84)sprint distances.Concurrently,variables such as relative maximal-strength,relative SJ parameters(height,peak force,and peak power),relative CMJ peak power,and reactive strength index(DJ from 35 cm height)had significant discriminative ability and correlations(P<0.05)with sprint distances involving maximal velocity and flying-start.Additionally,a combination of SJ height and relative maximal-strength during back-squat accounted for 75%of the variance in 60 m sprint times.Conclusions Relative measures of multiple strength metrics may provide better insight regarding factors that enhance sprint performance.Adequate maximal-strength,high explosive power,and reactive strength seem necessary to improve sprint performance in young male elite sprinters.