Designing,building, measuring,and testing a constant equivalent fall height terrain park jump

Previous work has presented both a theoretical foundation for designing terrain park jumps that control landing impact and computer software to accomplish this task. US ski resorts have been reluctant to adopt this more engineered approach to jump design, in part due to questions of feasibility. The present study demonstrates this feasibility. It describes the design, construction, measurement, and experimental testing of such a jump. It improves on the previous efforts with more complete instrumentation, a larger range of jump distances, and a new method for combining jumper- and board-mounted accelerometer data to estimate equivalent fall height, a measure of impact severity. It unequivocally demonstrates the efficacy of the engineering design approach, namely that it is possible and practical to design and build free style terrain park jumps with landing surface shapes that control for landing impact as predicted by the theory.     

Relationship between foot strike pattern,running speed,and footwear condition in recreational distance runners

Compared to competitive runners, recreational runners appear to be more prone to injuries, which have been associated with foot strike patterns. Surprisingly, only few studies had examined the foot strike patterns outside laboratories. Therefore, this study compared the foot strike patterns in recreational runners at outdoor tracks with previously reported data. We also investigated the relationship between foot strike pattern, speed, and footwear in this cohort. Among 434 recreational runners analysed, 89.6% of them landed with rearfoot strike (RFS). Only 6.9 and 3.5% landed with midfoot and forefoot, respectively. A significant shift towards non-RFS was observed in our cohort, when compared with previously reported data. When speed increased by 1 m/s, the odds of having forefoot strike and midfoot strike relative to RFS increased by 2.3 times and 2.6 times, respectively. Runners were 9.2 times more likely to run with a forefoot strike in minimalists compared to regular running shoes, although 70% of runners in minimalists continued to use a RFS. These findings suggest that foot strike pattern may differ across running conditions and runners should consider these factors in order to mitigate potential injury.     

‘The life of crime does not pay; stop and think!’: the process of co-constructing a prototype pedagogical model of sport for working with youth from socially vulnerable backgrounds

Purpose: This study discusses the process of co-constructing a prototype pedagogical model for working with youth from socially vulnerable backgrounds.

Participants and settings: This six-month activist research project was conducted in a soccer program in a socially vulnerable area of Brazil in 2013. The study included 17 youths, 4 coaches, a pedagogic coordinator and a social worker. An expert in student-centered pedagogy and inquiry-based activism assisted as a debriefer helping in the progressive data analysis and the planning of the work sessions.

Data collection/analysis: Multiple sources of data were collected, including 38 field journal/observation and audio records of: 18 youth work sessions, 16 coaches’ work sessions, 3 combined coaches and youth work sessions, and 37 meetings between the researcher and the expert.

Findings: The process of co-construction of this prototype pedagogical model was divided into three phases. The first phase involved the youth and coaches identifying barriers to sport opportunities in their community. In the second phase, the youth, coaches and researchers imagined alternative possibilities to the barriers identified. In the final phase, we worked collaboratively to create realistic opportunities for the youth to begin to negotiate some of the barriers they identified. In this phase, the coaches and youth designed an action plan to implement (involving a Leadership Program) aimed at addressing the youths’ needs in the sport program. Five critical elements of a prototype pedagogical model were co-created through the first two processes and four learning aspirations emerged in the last phase of the project.

Implications: We suggest an activist approach of co-creating a pedagogical model of sport for working with youth from socially vulnerable backgrounds is beneficial. That is, creating opportunities for youth to learn to name, critique and negotiate barriers to their engagement in sport in order to create empowering possibilities.     

Quiet eye training aids the long-term learning of throwing and catching in children: Preliminary evidence for a predictive control strategy

Abstract

Quiet eye training (QET) may be a more effective method for teaching children to catch than traditional training (TT) methods, but it is unclear if the benefits accrued persist in the long term. Thirty children were randomly allocated into a QET or TT group and, while wearing a mobile eye tracker, underwent baseline testing, training and two retention tests over a period of eight weeks, using a validated throw and catch task. During training, movement-related information was provided to both groups, while the QET group received additional instruction to increase the duration of their targeting fixation (QE1) on the wall prior to the throw, and pursuit tracking (QE2) period on the ball prior to catching. In both immediate (R1) and delayed (R2, six weeks later) retention tests, the QET group had a significantly longer QE1 duration and an earlier and longer QE2 duration, compared to the TT group, who revealed no improvements. A performance advantage was also found for the QET compared to the TT group at both R1 and R2, revealing the relatively robust nature of the visuomotor alterations. Regression analyses suggested that only the duration of QE1 predicted variance in catch success post-training, pointing to the importance of a pre-programming visuomotor strategy for successful throw and catch performance.     

A grounded theory of positive youth development through sport based on results from a qualitative meta-study

The overall purpose of this study was to create a model of positive youth development (PYD) through sport grounded in the extant qualitative literature. More specifically, the first objective was to review and evaluate qualitative studies of PYD in sport. The second objective was to analyze and synthesize findings from these studies. Following record identification and screening, 63 articles were retained for analysis. Meta-method analysis revealed strengths of studies were the use of multiple data collection and validity techniques, which produced high-quality data. Weaknesses were limited use of ‘named’ methodologies and inadequate reporting of sampling procedures. Philosophical perspectives were rarely reported, and theory was used sparingly. Results of an inductive meta-data analysis produced three categories: PYD climate (adult relationships, peer relationships, and parental involvement), life skills program focus (life skill building activities and transfer activities), and PYD outcomes (in personal, social, and physical domains). A model that distinguishes between implicit and explicit processes to PYD is presented.     

Sport-based physical activity intervention on body weight in children and adolescents: a meta-analysis

Controversial results reported in past research pertaining to the effectiveness of sport-based physical activity interventions on weight loss. The purpose of this study was to assess the impact of sport-based physical activity intervention on body weight in children and adolescents using a meta-analysis. Academic Search Complete, Education Source, ERIC, Medline, ProQuest, PsycINFO and SportDiscus databases were searched from January 2000 to April 2015. Eighteen studies met following inclusion criteria: sport-based intervention studies; subjects aged 6–18 years; reported body weight; published in peer-reviewed journals written in English. The mean intervention duration was 17.72 weeks. The overall effect size (ES) was 0.52 (Cohen’s d (ES) = 0.52, 95% CI = 0.08, 0.95, P = 0.021), using a random effects model. Moderator analyses results showed that the Q statistic for the sport type (individual sport or team sport, Qbetween (Q_b) = 14.52, df = 1, P = 0.001) and diet control (Qbetween (Q_b) = 8.85, df = 1, P = 0.001), explained the heterogeneity of ESs. Our study showed that there was a moderate overall effect of sport-based physical activity intervention on body weight reduction. The team sport type (ES = 1.05, 95% CI = 0.44, 1.66) and diet control group (ES = 0.84, 95% CI = 0.26, 1.41) appeared to be more effective in reducing body weight.     

Evidence for data missing at random in youth physical activity monitoring research

This study examined whether or not activity monitor data collected as part of a typical 7-day physical activity (PA) measurement protocol can be expected to be missing at random. A total of 315 participants (9–18 years) each wore a SenseWear Armband monitor for 7 consecutive days. Participants were classified as “compliant” (86 boys and 124 girls) if they had recorded accelerometer data during 70% or more of the predefined awake time (7 AM–10 PM) on four different days; and “non-compliant” (44 boys and 51 girls) when not meeting these criteria. Linear mixed models were used to examine differences in energy expenditure (EE) levels by compliance across 10 different time periods. The results indicated that non-compliant girls were older (13.4 ± 2.9 vs. 12.2 ± 2.5) and taller (156.8 ± 10.3 vs. 152.8 ± 11.3) than their same gender compliant peers (P < .05). Comparisons of EE rates at segmented portions of the day revealed no differences between compliant and non-compliant groups (P ≥ .05). Differences in EE ranged from ?0.32 kcal · kg^?1 · h^?1 (before school time) to 0.62 kcal · kg^?1 · h^?1 (physical education class) in boys and ?0.39 kcal · kg^?1 · h^?1 (transportation from school) to 0.37 kcal · kg^?1 · hour^?1 (recess) in girls. The results showed that compliant and non-compliant individuals differed in a few demographic characteristics but exhibited similar activity patterns. This suggests that data were considered to be missing at random, but additional work is needed to confirm this observation in a representative sample of children using other types of activity monitors and protocols.     

Estimating fat-free mass in elite-level male rowers: a four-compartment model validation of laboratory and field methods

The purpose of this study was to investigate the accuracy of fat-free mass (FFM) estimates from two-compartment (2C) models including air displacement plethysmography (ADP), ultrasound (US), near-infrared interactance (NIR), and the Jackson and Pollock skinfold equation (SKF) against a criterion four-compartment (4C) model in elite male rowers. METHODS: Twenty-three elite-level male rowers (mean± SD; age 24.6 ± 2.2 years; stature: 191.4 ± 7.2 cm; mass: 87.2 ± 11.2 kg) participated in this investigation. All body composition assessments were performed on the same day in random order, except for hydrostatic weighing (HW), which was measured last. FFM was evaluated using a 4C model, which included total body water from bioimpedance spectroscopy, body volume from HW, and total body bone mineral via dual-energy X-ray absorptiometry. The major findings of the study were that the 2C models evaluated overestimated FFM and should be considered with caution for the assessment of FFM in elite male rowers. Future studies should use multiple-compartment models, with measurement of TBW and bone mineral content, for the estimation of FFM.     

Effects of heat acclimation on hand cooling efficacy following exercise in the heat

This study examined the separate and combined effects of heat acclimation and hand cooling on post-exercise cooling rates following bouts of exercise in the heat. Seventeen non-heat acclimated (NHA) males (mean ± SE; age, 23 ± 1 y; mass, 75.30 ± 2.27 kg; maximal oxygen consumption [VO₂ max], 54.1 ± 1.3 ml·kg^?1·min^?1) completed 2 heat stress tests (HST) when NHA, then 10 days of heat acclimation, then 2 HST once heat acclimated (HA) in an environmental chamber (40°C; 40%RH). HSTs were 2 60-min bouts of treadmill exercise (45% VO₂ max; 2% grade) each followed by 10 min of hand cooling (C) or no cooling (NC). Heat acclimation sessions were 90–240 min of treadmill or stationary bike exercise (60–80% VO₂ max). Repeated measures ANOVA with Fishers LSD post hoc (α < 0.05) identified differences. When NHA, C (0.020 ± 0.003°C·min^?1) had a greater cooling rate than NC (0.013 ± 0.003°C·min^?1) (mean difference [95%CI]; 0.007°C [0.001,0.013], P = 0.035). Once HA, C (0.021 ± 0.002°C·min^?1) was similar to NC (0.025 ± 0.002°C·min^?1) (0.004°C [?0.003,0.011], P = 0.216). Hand cooling when HA (0.021 ± 0.002°C·min^?1) was similar to when NHA (0.020 ± 0.003°C·min^?1) (P = 0.77). In conclusion, when NHA, C provided greater cooling rates than NC. Once HA, C and NC provided similar cooling rates.     

Kicking modality during erratic-dynamic and static condition effects the muscular co-activation of attacker

The purpose of the study was to investigate the effect of different kicking modality, i.e., erratic-dynamic target (EDT) versus static target (ST) on the performance of the roundhouse kick in two groups of taekwondo athletes of different skill level. Three-dimensional analysis and surface electromyography (SEMG) analysis were performed on 12 (Group A: six sub-elite, Group B: six elite) athletes to investigate muscle co-activation pattern under two conditions, i.e., EDT versus ST. In the results, the muscle recruitment ratio of the agonistic muscles was higher for Group A, whereas Group B had higher recruitment ratio for antagonist muscles. Overall, the co-activation index (CI) of hip joints appeared higher in the extensors for Group A, whereas higher CI was observed in flexor muscles for Group B with comparatively higher CI during EDT condition than ST condition. Higher value of CI was observed in flexor muscles of the knee joints among Group A during EDT conditions, in contrast, higher CI in the extensor muscles was observed among Group B during ST conditions. In conclusion, the study confirmed that erratic-dynamic movements of target could change the movement coordination pattern to maintain the joint stability of participants.