The cumulative and residual fatigue response associated with soccer-specific activity performed on different playing surfaces

ABSTRACT

This study aimed to assess the effect of playing surface (Natural [NT] and Artificial [AT] Turf) on the fatigue response to a soccer-specific exercise protocol (SSEP). Eighteen male soccer players completed the SSEP on NT and AT with pre-, post-, and 48 h post-assessments of eccentric knee flexor (eccKF) and concentric knee extensor peak torque (PT), peak countermovement (CMJ) and squat jump (SJ) height, and Nordic hamstring break angle. No significant main effects for surface or any surface and time interactions were observed for any of the outcome measures, except for eccKF PT recorded at 3.14 rad·s^-1, which was significantly lower 48 h post-trial in the AT condition (AT = 146.3 ± 20.4 Nm; NT = 158.8 ± 24.7 Nm). Main effects for time were observed between pre- and post-trial measures for eccKF PT at all angular velocities, Nordic break angle, CMJ and SJ height. Nordic break angle, and both CMJ and SJ height were significantly impaired 48 h post-trial when compared to pre-trial. The findings of the current study suggest surface dependent changes in eccKF PT which may have implications for recovery and subsequent performance after competition on AT.     

Bounding,An Accessible Method for Estimating Principal Causal Effects,Examined and Explained

Estimating treatment effects for subgroups defined by posttreatment behavior (i.e., estimating causal effects in a principal stratification framework) can be technically challenging and heavily reliant on strong assumptions. We investigate an alternative path: using bounds to identify ranges of possible effects that are consistent with the data. This simple approach relies on fewer assumptions and yet can result in policy-relevant findings. As we show, even moderately predictive covariates can be used to substantially tighten bounds in a straightforward manner. Via simulation, we demonstrate which types of covariates are maximally beneficial. We conclude with an analysis of a multisite experimental study of Early College High Schools. When examining the program's impact on students completing the ninth grade “on-track” for college, we find little impact for ECHS students who would otherwise attend a high-quality high school, but substantial effects for those who would not. This suggests a potential benefit in expanding these programs in areas primarily served by lower quality schools.     

Parameters in television captioning for deaf and hard-of-hearing adults: effects of caption rate versus text reduction on comprehension

Caption rate and text reduction are factors that appear to affect the comprehension of captions by people who are deaf or hard of hearing. These 2 factors are confounded in everyday captioning; rate (in words per minute) is slowed by text reduction. In this study, caption rate and text reduction were manipulated independently in 2 experiments to assess any differential effects and possible benefits for comprehension by deaf and hard-of-hearing adults. Volunteers for the study included adults with a range of reading levels, self-reported hearing status, and different communication and language preferences. Results indicate that caption rate (at 130, 180, 230 words per minute) and text reduction (at 84%, 92%, and 100% original text) have different effects for different adult users, depending on hearing status, age, and reading level. In particular, reading level emerges as a dominant factor: more proficient readers show better comprehension than poor readers and are better able to benefit from caption rate and, to some extent, text reduction modifications.     

Elementary teachers’ science subject matter knowledge across the teacher career cycle

Although widely touted as important, there is little evidence regarding the influence of teaching experience on elementary teachers' science subject matter knowledge (SMK). To better understand this phenomenon, we administered an assessment of science topics taught in the fifth and sixth grades to 169 preservice teachers, 231 fifth-grade teachers, and 208 sixth-grade teachers. We then compared the mean scores of teachers at different stages in the career cycle using one-way and two-way ANOVA and explored the relationship between SMK scores and years of teaching experience using regression analysis. Findings indicate that (i) being assigned to a specific grade level had an impact on teachers' SMK for topics included in the grade level, (ii) teachers' SMK scores were lower later in their careers for both science topics they had never taught and for science topics they were responsible for teaching, and (iii) results differed for fifth and sixth grades. This study adds to the existing literature through the examination of a large sample of elementary teachers, with teachers of varying years of experience, while focusing on the science topics these teachers are responsible for teaching. The results of this study provide strong evidence that (i) years of experience teaching specific science topics is associated with the development of teachers' knowledge of these topics, and (ii) teaching experience, what teachers do in the context of their everyday practice, can be an effective means of self-directed learning for teachers. There is also evidence that this influence is not uniform across years of teaching experience or science topics taught. These findings raise important implications about future research into the mechanism of SMK development through teaching experience and teacher grade-level assignments.     

The second leg home advantage: evidence from European football cup competitions

The home advantage is a widely acknowledged sporting phenomenon, especially in association football. Here, we examine the second leg home advantage, an effect that is discussed in the public domain but which has received very little scientific attention. The second leg home advantage effect occurs when on average teams are more likely to win a two-stage knock-out competition when they play at home in the second leg. That is, both teams have a home advantage but this advantage is significantly greater for the team that plays at home second. Examining data from three different European Cup football competitions spanning 51 years, we show that the second leg home advantage is a real phenomenon. The second leg home team has more than a 50% probability to qualify for the next round in the competition even after controlling for extra time and team ability as possible alternative explanations. The second leg home advantage appears, however, to have decreased significantly over the past decade. Possible reasons for its existence and subsequent decline are presented.     

Relationship between maximal oxygen uptake and oxygen uptake attained during treadmill middle-distance running

Traditionally, it has been assumed that during middle-distance running oxygen uptake (VO2) reaches its maximal value (VO2max) providing the event is of a sufficient duration; however, this assumption is largely based on observations in individuals with a relatively low VO2max. The aim of this study was to determine whether VO2max is related to the VO2 attained (i.e. VO2peak) during middle-distance running on a treadmill. Fifteen well-trained male runners (age 23.3 +/- 3.8 years, height 1.80 +/- 0.10 m, body mass 76.9 +/- 10.6 kg) volunteered to participate in the study. The participants undertook two 800-m trials to examine the reproducibility of the VO2 response. These two trials, together with a progressive test to determine VO2max, were completed in a randomized order. Oxygen uptake was determined throughout each test using 15-s Douglas bag collections. Following the application of a 30-s rolling average, the highest VO2 during the progressive test (i.e. VO2max) was compared with the highest VO2 during the 800-m trials (i.e. VO2peak) to examine the relationship between VO2max and the VO2 attained in the 800-m trials. For the 15 runners, VO2max was 58.9 +/- 7.1 ml x kg(-1) x min(-1). Two groups were formed using a median split based on VO2max. For the high and low VO2max groups, VO2max was 65.7 +/- 3.0 and 52.4 +/- 1.8 ml x kg(-1) x min(-1) respectively. The limits of agreement (95%) for test-retest reproducibility for the VO2 attained during the 800-m trials were +/- 3.5 ml x kg(-1) x min(-1) for a VO2peak of 50.6 ml x kg(-1) x min(-1) (the mean VO2peak for the low VO2max group) and +/- 2.3 ml x kg(-1) x min(-1) for a VO2peak of 59.0 ml x kg(-1) x min(-1) (the mean VO2peak for the high VO2max group), with a bias in VO2peak between the 800-m runs (i.e. the mean difference) of 1.2 ml x kg(-1) x min(-1). The VO2peak for the 800-m runs was 54.8 +/- 4.9 ml x kg(-1) x min(-1) for all 15 runners. For the high and low VO2max groups, VO2peak was 59.0 +/- 3.3 ml x kg(-1) x min(-1) (i.e. 90% VO2max) and 50.6 +/- 2.0 ml x kg(-1) x min(-1) (i.e. 97% VO2max) respectively. The negative relationship (-0.77) between VO2max and % VO2max attained for all 15 runners was significant (P = 0.001). These results demonstrate that (i) reproducibility is good and (ii) that VO2max is related to the %VO2max achieved, with participants with a higher VO2max achieving a lower %VO2max in an 800-m trial on a treadmill.