“Biological Background of Block Periodized Endurance Training: A Review”

Reply to Kiely et al.: Comment on: “Biological Background of Block Periodized Endurance Training: A Review”

Causal Mediation Analysis Could Resolve Whether Training-Induced Increases in Muscle Strength are Mediated by Muscle Hypertrophy Abstract Resistance training increases muscle size (i.e., causes hypertrophy) and muscle strength, particularly in untrained individuals. Hypertrophy is widely believed to be one of the mechanisms (i.e., a mediator) by which resistance training increases strength. However, some researchers have questioned whether training-induced hypertrophy causes increases in strength. One approach to resolving this issue has been to use correlations between training-induced changes in muscle size and strength to infer the effect of hypertrophy on strength. This is problematic because correlations between changes in muscle size and strength may be confounded (i.e., correlation is not causation). Another approach has involved randomizing participants to different volumes of exercise to create different levels of hypertrophy and then comparing the strength increases associated with different levels of hypertrophy. This approach is also problematic because the unit of randomization is exercise volume rather than hypertrophy, and the potential for confounding remains. Thus, a new approach is needed to determine the extent to which hypertrophy increases muscle strength. Here, we introduce resistance training researchers to causal mediation analysis and recommend that it be used to resolve the current debate. Causal mediation analysis potentially provides an unconfounded estimate of the effect of a mediating variable (hypertrophy) on an outcome (strength). This analysis is supplemented by causal maps that help conceptualize research questions and identify potential confounders. In addition to resolving the debate on hypertrophy, causal mediation analysis can be used to answer a host of other questions about mechanisms in the health sciences.

Effects of Exercise Compression Stockings on Anterior Muscle Compartment Pressure and Oxygenation During Running: A Randomized Crossover Trial Conducted in Healthy Recreational Runners Abstract Background Exercise compression garments have increased in popularity among athletes at all levels during the last 10 years. However, the scientific grounds for this are unclear. The purpose of the present study was to examine the effect of wearing exercise compression stockings (CS) on the anterior compartment pressure, oxygenation of the tibialis anterior muscle, and early blood biomarkers change for muscle damage during a 10-km treadmill run in healthy subjects. Methods Twenty healthy subjects completed two identical treadmill runs, with or without CS. The subjects were randomized regarding the order in which the sessions were performed. Intramuscular pressure (IMP) and muscle oxygenation in the one leg were continuously measured before, during, and after running sessions. Blood samples were collected just before and directly after these sessions and analyzed for myoglobin and creatine kinase concentrations. Results The use of CS during running resulted in significantly higher IMP (by 22 ± 3.1 mmHg on average) and lower tissue oxygenation index (by 11 ± 1.8%) compared to running without CS (p < 0.001). In addition, the Δ change in median serum myoglobin concentration measured before and after running was significantly higher when CS were used: 58 (9‒210) µg/L as compared to 38 (0‒196) µg/L with no CS (p = 0.04). No difference in post-running early serum creatine kinase concentration was observed between using CS and not using CS. Conclusion Wearing exercise CS during and following a 10-km treadmill run elevated IMP and reduced muscle tissue oxygenation in the anterior compartment of healthy runners. Furthermore, the use of exercise CS did not prevent early exercise-induced muscle damage, as measured by serum biomarkers.

Physiological Impact and Clinical Relevance of Passive Exercise/Movement Abstract Passive exercise/movement has a long history in both medicine and physiology. Early clinical applications of passive exercise/movement utilized pneumatic and direct limb compression to stimulate the vasculature and evoke changes in blood flow to avoid complications brought about by stasis and vascular disease. Over the last 50 years, passive exercise/movement has continued to progress and has provided physiologists with a reductionist approach to mechanistically examine the cardiorespiratory, hyperemic, and afferent responses to movement without the confounding influence of metabolism that accompanies active exercise. This review, in addition to providing an historical perspective, focuses on the recent advancements utilizing passive leg movement, and how the hyperemic response at the onset of this passive movement has evolved from a method to evaluate the central and peripheral regulation of blood flow during exercise to an innovative and promising tool to assess vascular function. As an assessment of vascular function, passive leg movement is relatively simple to perform and provides a nitric oxide-dependent evaluation of endothelial function across the lifespan that is sensitive to changes in activity/fitness and disease state (heart failure, peripheral artery disease, sepsis). The continual refinement and characterization of passive leg movement are aimed at improving our understanding of blood flow regulation and the development of a clinically ready approach to predict and monitor the progression of cardiovascular disease.

Role of Physical Activity and Sedentary Behavior in the Mental Health of Preschoolers, Children and Adolescents: A Systematic Review and Meta-Analysis Abstract Background Evidence suggests that participation in physical activity may support young people’s current and future mental health. Although previous reviews have examined the relationship between physical activity and a range of mental health outcomes in children and adolescents, due to the large increase in published studies there is a need for an update and quantitative synthesis of effects. Objectives The objectives of this study were to determine the effect of physical activity interventions on mental health outcomes by conducting a systematic review and meta-analysis, and to systematically synthesize the observational evidence (both longitudinal and cross-sectional studies) regarding the associations between physical activity and sedentary behavior and mental health in preschoolers (2–5 years of age), children (6–11 years of age) and adolescents (12–18 years of age). Methods A systematic search of the PubMed and Web of Science electronic databases was performed from January 2013 to April 2018, by two independent researchers. Meta-analyses were performed to examine the effect of physical activity on mental health outcomes in randomized controlled trials (RCTs) and non-RCTs (i.e. quasi-experimental studies). A narrative synthesis of observational studies was conducted. Studies were included if they included physical activity or sedentary behavior data and at least one psychological ill-being (i.e. depression, anxiety, stress or negative affect) or psychological well-being (i.e. self-esteem, self-concept, self-efficacy, self-image, positive affect, optimism, happiness and satisfaction with life) outcome in preschoolers, children or adolescents. Results A total of 114 original articles met all the eligibility criteria and were included in the review (4 RCTs, 14 non-RCTs, 28 prospective longitudinal studies and 68 cross-sectional studies). Of the 18 intervention studies, 12 (3 RCTs and 9 non-RCTs) were included in the meta-analysis. There was a small but significant overall effect of physical activity on mental health in children and adolescents aged 6–18 years (effect size 0.173, 95% confidence interval 0.106–0.239, p < 0.001, percentage of total variability attributed to between-study heterogeneity [I2] = 11.3%). When the analyses were performed separately for children and adolescents, the results were significant for adolescents but not for children. Longitudinal and cross-sectional studies demonstrated significant associations between physical activity and lower levels of psychological ill-being (i.e. depression, stress, negative affect, and total psychological distress) and greater psychological well-being (i.e. self-image, satisfaction with life and happiness, and psychological well-being). Furthermore, significant associations were found between greater amounts of sedentary behavior and both increased psychological ill-being (i.e. depression) and lower psychological well-being (i.e. satisfaction with life and happiness) in children and adolescents. Evidence on preschoolers was nearly non-existent. Conclusions Findings from the meta-analysis suggest that physical activity interventions can improve adolescents’ mental health, but additional studies are needed to confirm the effects of physical activity on children’s mental health. Findings from observational studies suggest that promoting physical activity and decreasing sedentary behavior might protect mental health in children and adolescents. PROSPERO Registration Number: CRD42017060373.

Methodological Issues in Soccer Talent Identification Research Abstract Talent identification research in soccer comprises the prediction of elite soccer performance. While many studies in this field have aimed to empirically relate performance characteristics to subsequent soccer success, a critical evaluation of the methodology of these studies has mostly been absent in the literature. In this position paper, we discuss advantages and limitations of the design, validity, and utility of current soccer talent identification research. Specifically, we draw on principles from selection psychology that can contribute to best practices in the context of making selection decisions across domains. Based on an extensive search of the soccer literature, we identify four methodological issues from this framework that are relevant for talent identification research, i.e. (1) the operationalization of criterion variables (the performance to be predicted) as performance levels; (2) the focus on isolated performance indicators as predictors of soccer performance; (3) the effects of range restriction on the predictive validity of predictors used in talent identification; and (4) the effect of the base rate on the utility of talent identification procedures. Based on these four issues, we highlight opportunities and challenges for future soccer talent identification studies that may contribute to developing evidence-based selection procedures. We suggest for future research to consider the use of individual soccer criterion measures, to adopt representative, high-fidelity predictors of soccer performance, and to take restriction of range and the base rate into account.

Running Biomechanics in Individuals with Anterior Cruciate Ligament Reconstruction: A Systematic Review Abstract Background A return to running after anterior cruciate ligament reconstruction (ACL-R) is critical to the clinical success of any cutting and pivoting athlete who wishes to return to sport. Knowledge of specific alterations during running after ACL-R is required to optimise rehabilitation for improving outcomes and long-term disability. Objective The objective of this systematic review was to summarise kinematic, kinetic and muscle activation data during running after ACL-R and the intrinsic factors (e.g. surgical technique and strength asymmetries) affecting running biomechanics. Methods MEDLINE, EMBASE, SPORTDiscus and CINAHL databases were searched from inception to 10 December, 2018. The search identified studies comparing kinematic, kinetic or muscle activation data during running between the involved limb and contralateral or control limbs. Studies analysing the effect of intrinsic factors in the ACL-R group were also included. Risk of bias was assessed, qualitative and quantitative analyses performed, and levels of evidence determined. Results A total of 1993 papers were identified and 25 were included for analysis. Pooled analyses reported a deficit of knee flexion motion and internal knee extension moment, compared with both contralateral or control limbs, during the stance phase of running from 3 months to 5 years after ACL-R (strong evidence). Inconsistent results were found for both peak vertical ground reaction force and impact forces after ACL-R. Patellofemoral and tibiofemoral joint contact forces differed from both contralateral or control limbs up until at least 2.5 years after ACL-R and moderate evidence indicated no difference for muscle activations during moderate speed running. Quadriceps and hamstring strength asymmetries, and knee function, but not surgical techniques, were likely to be associated with both knee kinematics and kinetics during running after ACL-R. Conclusion After ACL-R, knee flexion motion and internal knee extension moment are the most affected variables and are consistently smaller in the injured limb during running when pooling evidence. Clinicians should be aware that these deficits do not appear to resolve with time and, thus, specific clinical interventions may be needed to reduce long-term disability. Systematic review registration Registered in PROSPERO 2017, CRD42017077130.

The Role of Hypernetworks as a Multilevel Methodology for Modelling and Understanding Dynamics of Team Sports Performance Abstract Despite its importance in many academic fields, traditional scientific methodologies struggle to cope with analysis of interactions in many complex adaptive systems, including team sports. Inherent features of such systems (e.g. emergent behaviours) require a more holistic approach to measurement and analysis for understanding system properties. Complexity sciences encompass a holistic approach to research on collective adaptive systems, which integrates concepts and tools from other theories and methods (e.g. ecological dynamics and social network analysis) to explain functioning of such systems in their natural environments. Multilevel networks and hypernetworks comprise novel and potent methodological tools for assessing team dynamics at more sophisticated levels of analysis, increasing their potential to impact on competitive performance in team sports. Here, we discuss how concepts and tools derived from studies of multilevel networks and hypernetworks have the potential for revealing key properties of sports teams as complex, adaptive social systems. This type of analysis can provide valuable information on team performance, which can be used by coaches, sport scientists and performance analysts for enhancing practice and training. We examine the relevance of network sciences, as a sub-discipline of complexity sciences, for studying the dynamics of relational structures of sports teams during practice and competition. Specifically, we explore the benefits of implementing multilevel networks, in contrast to traditional network techniques, highlighting future research possibilities. We conclude by recommending methods for enhancing the applicability of hypernetworks in analysing team dynamics at multiple levels.

Your Personal Motivator is with You: A Systematic Review of Mobile Phone Applications Aiming at Increasing Physical Activity Abstract Background Literature shows mixed evidence about the power of mobile phone applications to foster physical activity. A systematic integration that offers insights into which mobile phone application techniques can or cannot foster physical activity is lacking, as is a theoretical integration of current research. Objectives We performed a systematic review guided by a theoretical framework focusing on effects that certain mobile phone application techniques have on physical activity, to improve our understanding of what techniques are more or less effective. Methods We identified articles by searching EBSCO Business Source Complete, Science Direct, PsycINFO, Springer, PLoS ONE, Taylor and Francis, IEEE, Social Science Citation Index, Science Citation Index Expanded, PUBMED, MEDLINE, and Google Scholar. We considered articles if (1) they referred to the use of mobile phone applications to promote physical activity; (2) their methodological approach allowed one to derive appropriate results (e.g., intervention-based approach, observational study); (3) they were published in peer-reviewed journals or conference proceedings; and (4) they were written in English. The literature search resulted in 41 usable studies. Meta-synthesis and vote counting were applied to analyze these studies. Results Based on the ratio of supportive versus non-supportive evidence in both the qualitative and the quantitative studies, we propose the following descending rank order for the effectiveness of application techniques to foster physical activity. This is tentative in nature because the current overall small body of literature made coming to definite conclusions difficult: (1) feedback, (2) goal setting and its sub-forms, (3) competition, social sharing with familiar users in both segregated and social network groups, and (4) social sharing with strangers in segregated groups, reward, and social sharing with strangers in social network groups. Rewards in particular provided mixed results, and social sharing with strangers in segregated and social network groups seemed rather ineffective but may work under special conditions that need to be identified in additional research. One limitation of our study was that our results are mostly derived from qualitative studies, since quantitative studies are underrepresented in the field. Conclusion Several mobile phone application techniques were identified that have the potential to foster physical activity, whereas others were identified that are unlikely to increase physical activity. Major avenues for future research include more theoretical development and more quantitative studies, among others.