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.     

Acute fatigue negatively affects risk factors for injury in trained but not well-trained habitually shod runners when running barefoot

Introduction: Many factors may contribute to running-related injury. These include fatigue and footwear, the combination of which has rarely been studied, in particular with reference to barefoot running, recently advocated as a method to reduce injury risk. Methods: Twenty-two runners (12 well-trained and 10 trained) participated in a 10?km fatiguing trial. Knee and ankle joint kinematics and kinetics and electromyography were assessed during overground running in the barefoot and shod condition. This was performed pre- and post-fatigue using a motion capture system and force platforms. Results: Initial loading rate increased in the trained runners when barefoot but not shod. Shod knee stiffness increased in both groups after fatigue, whereas barefoot knee stiffness decreased only in the trained group. A reduction in barefoot bicep femoris pre-activation was found in both groups. During stance, a reduction in vastus lateralis and biceps femoris and an increase in tibialis anterior activity were found over time in both groups and conditions. Trained runners decreased gluteus medius and increased lateral gastrocnemius median frequency for both conditions after fatigue. Conclusion: When fatigued, gait adjustments in habitually shod runners may increase injury risk when running barefoot. Training status may be a risk factor for injury, as less-trained runners experience muscular fatigue changes that may compromise ground reaction force attenuation. Caution is recommended when transitioning to pure barefoot running.     

Sport disciplines,types of sports,and waist circumference in young adulthood – a population-based twin study

Purpose: The benefits of physical activity (PA) in preventing abdominal obesity are well recognized, but the role of different sport disciplines remains open. We aimed, therefore, to investigate how participation in different sport disciplines, and the number and types of sports engaged in are associated with waist circumference (WC) in young adulthood. Methods: This population-based cohort study comprised 4027 Finnish twin individuals (1874 men), with a mean age of 34 y (32–37), who answered a survey, including self-measured WC. We extracted the number and identified the types (aerobic, power, and mixed) of the different sport disciplines respondents reported participating in. Results: The number of sport disciplines participated in was inversely associated with WC, the linear decrease averaging 1.38?cm (95% CI 1.10–1.65) per each additional sport discipline. The result persisted after adjustment for the main covariates, such as volume of PA and diet quality. Among dizygotic twin pairs discordant for sports participation (0–2 vs. 5 or more disciplines), the mean within-pair difference in WC was 4.8?cm (95% CI 0.4–9.1) for men and 11.2?cm (95% CI 4.4–18.0) for women; among discordant monozygotic pairs, no differences were observed. In men, all three types of sports were individually associated with smaller WC, while in women, only mixed and power sports showed this association. Conclusions: Participation in several sport disciplines and sport types was associated with smaller WC among young adults in their mid-30s. Shared genetic background may explain some of the associations.     

Symptoms of common mental disorders and related stressors in Danish professional football and handball

The aim of the study was twofold, namely (i) to determine the prevalence of symptoms of common mental disorders (CMDs) among current and retired professional football and handball players and (ii) to explore the relationship of psychosocial stressors with the outcome measures under study. A total of 1155 players were enrolled in an observational study based on a cross-sectional design. Questionnaires based on validated scales were set up and distributed among current and retired professional football and handball players by the Danish football and handball players’ union. In professional football, the highest prevalence (4 weeks) of symptoms of CMDs was 18% and 19% for anxiety/depression among current and retired players, respectively. In professional handball, the highest prevalence (4 weeks) of symptoms of CMDs was 26% and 16% for anxiety/depression among current and retired players, respectively. For both the current and retired professional football and handball players, a higher number of severe injuries and recent adverse life events (LE) were related to the presence of symptoms of CMD. Players exposed to severe injuries and/or recent adverse LE were 20–50% times more likely to report symptoms of CMD. The results suggest that it is possible to recognize the population of professional athletes that are more likely to develop symptoms of CMD. This could create the opportunity to intervene preventively on athletes that suffered from severe injury and/or recent adverse LE that could lead to a faster and safer recovery and psychological readiness to return to play.     

Evaluating quality of implementation in physical activity interventions based on theories of motivation: current challenges and future directions

The evidence base pointing towards the maladaptive health consequences of an inactive lifestyle highlights the need for interventions that are effective in changing and maintaining physical activity behaviours. Theories of motivation are frequently applied to inform the content and delivery of such interventions. Systematic monitoring and evaluation of the quality of intervention implementation is therefore an important step in understanding if and how theories of motivation can be adopted and effectively applied to promote and/or sustain physical activity behaviours. However, intervention implementation quality in studies that aim to apply motivation theory to promote physical activity is often under-reported. The purpose of this article is, first, to review contemporary approaches used to monitor and evaluate intervention implementation; we outline the degree to which these methods have been used effectively in research concerned with applying theories of motivation to impact physical activity behaviours. Second, we identify and discuss specific challenges in effectively measuring quality of implementation faced by researchers who adopt a motivation theory basis to their work. Finally, recommendations for methods to monitor and evaluate intervention implementation in future trials aiming to promote physical activity based on theories of motivation are also proposed.     

Kinematic analysis of hip and knee rotation and other contributors to ballet turnout

Turnout, or external rotation (ER) of the lower extremities, is essential in ballet. The purpose of this study was to utilise physical examination and a biomechanical method for obtaining functional kinematic data using hip and knee joint centres to identify the relative turnout contributions from hip rotation, femoral anteversion, knee rotation, tibial torsion, and other sources. Ten female dancers received a lower extremity alignment assessment, including passive hip rotation, femoral anteversion, tibial torsion, weightbearing foot alignment, and Beighton hypermobility score. Next, turnout was assessed using plantar pressure plots and three-dimensional motion analysis; participants performed turnout to ballet first position on both a plantar pressure mat and friction-reducing discs. A retro-reflective functional marker motion capture system mapped the lower extremities and hip and knee joint centres. Mean total turnout was 129±15.7° via plantar pressure plots and 135±17.8° via kinematics. Bilateral hip ER during turnout was 49±10.2° (36% of total turnout). Bilateral knee ER during turnout was 41±5.9° (32% of total turnout). Hip ER contribution to total turnout measured kinematically was less than expected compared to other studies, where hip ER was determined without functional kinematic data. Knee ER contributed substantially more turnout than expected or previously reported. This analysis method allows precise assessment of turnout contributors.     

Influence of sex and limb dominance on lower extremity joint mechanics during unilateral land-and-cut manoeuvres

Limb dominance theory suggests that females tend to be more one-leg dominant and exhibit greater kinematic and kinetic leg asymmetries than their male counterparts, contributing to the increased risk of anterior cruciate ligament injury among female athletes. Thus, the purpose of this study was to examine the influences of sex and limb dominance on lower extremity joint mechanics during unilateral land-and-cut manoeuvres. Twenty-one women and 21 men completed land-and-cut manoeuvres on their dominant limb as well as their nondominant limb. Three-dimensional kinematics and kinetics were calculated bilaterally for the entire stance phase of the manoeuvre. Women performed land-and-cut manoeuvres with altered hip motions and loads as well as greater knee abduction at touchdown compared to men. Dominant limb land-and-cut manoeuvres where characterised by decreased hip flexion at touchdown as well as decreased hip flexion and adduction range of motion compared to nondominant land-and-cuts regardless of sex. The observed sex differences are consistent with previous research regarding mechanisms underlying the sex disparity in anterior cruciate ligament injury rates. However, observed differences regarding limb dominances appear somewhat arbitrary and did not suggest that the dominant or nondominant limb would be at increased risk of anterior cruciate ligament injury.     

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

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.     

Changes in kinematics and arm–leg coordination during a 100-m breaststroke swim

The purpose of this study was to compare arm–leg coordination and kinematics during 100 m breaststroke in 26 (8 female; 18 male) specialist breaststroke swimmers. Laps were recorded using three 50-Hz underwater cameras. Heart rate and blood lactate were measured pre- and post-swim. Arm–leg coordination was defined using coordination phases describing continuity between recovery and propulsive phases of upper and lower limbs: coordination phase 1 (time between end of leg kick and start of the arm pull phases); and coordination phase 2 (time between end of arm pull and start of leg kick phases). Duration of stroke phases, coordination phases, swim velocity, stroke length (SL), stroke rate (SR) and stroke index (SI) were analysed during the last three strokes of each lap that were unaffected by turning or finishing. Significant changes in velocity, SI and SL (P < 0.05) were found between laps. Both sexes showed significant increase (P < 0.05) in heart rate and blood lactate pre- to post-swim. Males had significantly (P < 0.01) faster swim velocities resulting from longer SLs (P = 0.016) with no difference in SR (P = 0.064). Sex differences in kinematic parameters can be explained by anthropometric differences providing males with increased propelling efficiency.     

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.