Target trial framework for determining the effect of changes in training load on injury risk using observational data: a methodological commentary.

In recent years, a large focus has been placed on managing training load for injury prevention. To minimise injuries, training recommendations should be based on research that examines causal relationships between load and injury risk. While observational studies can be used to estimate causal effects, conventional methods to study the relationship between load and injury are prone to bias. The target trial framework is a valuable tool that requires researchers to emulate a hypothetical randomised trial using observational data. This framework helps to explicitly define research questions and design studies in a way that estimates causal effects. This article provides an overview of the components of the target trial framework as applied to studies on load and injury and describes various considerations that should be made in study design and analyses to minimise bias.

Principles of musculoskeletal sport injuries for epidemiologists: a review.

BACKGROUND: Musculoskeletal injuries are a common occurrence in sport. The goal of sport injury epidemiology is to study these injuries at a population level to inform their prevention and treatment. MAIN BODY: This review provides an overview of musculoskeletal sport injuries and the musculoskeletal system from a biological and epidemiologic perspective, including injury mechanism, categorizations and types of sport injuries, healing, and subsequent injuries. It is meant to provide a concise introductory substantive background of musculoskeletal sport injuries for epidemiologists who may not have formal training in the underlying anatomy and pathophysiology. CONCLUSION: An understanding of sport injuries is important for researchers in sport injury epidemiology when determining how to best define and assess their research questions and measures.

Physical activity, organized sport participation and active transportation to school among Canadian youth by gender identity and sexual attraction. / Activité physique, participation à des sports organisés et utilisation du transport actif pour se rendre à l'école chez les adolescents canadiens par identité de genre et par orientation sexuelle.

INTRODUCTION: Regular physical activity is associated with a wide range of health benefits in youth. While previous studies have identified disparities in physical activity among youth by gender identity and sexual attraction, these have seldom been explored in Canadian youth. METHODS: Data from the 2019 Canadian Health Survey on Children and Youth were used to assess prevalence of and time spent in organized sports participation, total physical activity and active transportation by gender identity (non-cisgender vs. cisgender) among youth aged 12 to 17, and by sexual attraction (nonheterosexual attraction vs. heterosexual attraction) among youth aged 15 to 17. RESULTS: There was no difference in average minutes of total physical activity per week between non-cisgender and cisgender Canadian youth. Non-cisgender youth (which represent 0.5% of the population) averaged significantly fewer minutes of organized sports per week than their cisgender counterparts. There was some evidence of increased active transportation to school among non-cisgender youth, but insufficient power to detect significant differences. Canadian youth reporting any nonheterosexual attraction (which represent 21.2% of the population, including mostly heterosexual youth) were less likely to be regularly physically active and participate in organized sports than youth reporting exclusive heterosexual attraction. Differences were larger among males than females. Males reporting nonheterosexual attraction were more likely to use active transportation to get to school than their heterosexual counterparts. CONCLUSION: Non-cisgender youth and youth reporting nonheterosexual attraction tended to participate less in organized sports than their counterparts, but may have engaged in more active transportation. Mitigating the barriers associated with sport participation could increase physical activity among these groups.

Gender identity and sexual attraction among Canadian youth: findings from the 2019 Canadian Health Survey on Children and Youth. / Identité de genre et attirance sexuelle chez les jeunes Canadiens : résultats de l'Enquête canadienne sur la santé des enfants et des jeunes de 2019.

Gender identity and sexual attraction are important determinants of health. This study reports distributions of gender identity and sexual attraction among Canadian youth using data from the 2019 Canadian Health Survey on Children and Youth. Among youth aged 12 to 17, 0.2% are nonbinary and 0.2% are transgender. Among youth aged 15 to 17, 21.0%, comprising more females than males, report attraction not exclusive to the opposite gender. Given known associations between health and gender and sexual attraction, oversampling of sexual minority groups is recommended in future studies to obtain reliable estimates for identifying inequities and informing policy.

Gender and sexual attraction as a dimension of sexual orientation are important determinants of health among youth. Collecting gender and sexual attraction information as a routine part of public health surveillance is important for identifying inequities and informing policy. This study provides nationally representative estimates for the distribution of gender and sexual attraction among Canadian youth. This study identifies populations (nonbinary, transgender and same gender­attracted youth) that require oversampling or other approaches to ensure that reliable estimates can be obtained in public health surveillance.

Le genre et l'attirance sexuelle en tant que dimension de l'orientation sexuelle sont des déterminants importants de la santé chez les jeunes. La collecte de renseignements sur le genre et l'attirance sexuelle dans le cadre des activités habituelles de surveillance de la santé publique est importante pour relever les iniquités et orienter les politiques. Cette étude fait état d'estimations représentatives à l'échelle nationale de la répartition des genres et de l'attirance sexuelle chez les jeunes Canadiens. Cette étude répertorie les populations (non binaires, transgenres et jeunes ayant une attirance envers des personnes du même genre) devant faire l'objet d'un suréchantillonnage ou d'autres approches afin de garantir que des estimations fiables puissent être obtenues dans le cadre de la surveillance de la santé publique.

Associations of sleep duration and sleep quality with indicators of mental health among youth and adults: findings from the 2015 Canadian Community Health Survey. / Associations entre durée et qualité du sommeil et indicateurs de santé mentale chez les jeunes et les adultes : résultats de l'Enquête sur la santé dans les collectivités canadiennes de 2015.

INTRODUCTION: A growing number of Canadian studies have examined the link between sleep and mental health. This research builds upon that work by investigating associations of sleep duration and quality with positive mental health (PMH) and mental illness and suicidal ideation (MI/SI) outcomes among youth and adults from threeCanadian provinces (i.e. Ontario, Manitoba and Saskatchewan). METHODS: Using cross-sectional data from respondents 12 years and older (n = 18 683) who were asked questions on their sleep in the 2015 Canadian Community Health Survey - Annual Component, we conducted unadjusted and adjusted logistic regressionswith self-reported measures of sleep duration and sleep quality as independent variables and a range of PMH (e.g. high self-rated mental health) and MI/SI indicators (e.g. mood disorder diagnosis) as dependent variables. Analyses were conducted of allcomplete cases and also stratified by sex and age group. RESULTS: Good sleep quality was associated with higher odds of PMH indicators (adjusted odds ratio [aOR]: 1.52-4.24) and lower odds of MI/SI indicators (aOR: 0.23- 0.47); associations remained significant when analyses were stratified. Meeting sleep duration recommendations was positively associated with PMH indicators (aOR: 1.27- 1.56) and negatively associated with MI/SI indicators (aOR: 0.41-0.80), but some associations did not remain significant when stratified. CONCLUSION: This study provides support for associations between sleep duration and quality and indicators of PMH and MI/SI. Findings can inform future research and surveillance efforts that monitor sleep behaviours and indicators of PMH and MI/SI.

Injuries among Canadian children and youth: an analysis using the 2019 Canadian Health Survey on Children and Youth. / Blessures chez les enfants et les jeunes canadiens : analyse reposant sur les données de l'Enquête canadienne sur la santé des enfants et des jeunes de 2019.

This work provides an overview of injury patterns in Canadian children and youth aged 1 to 17 years. Self-reported data from the 2019 Canadian Health Survey on Children and Youth were used to calculate estimates for the percentage of Canadian children and youth who experienced a head injury or concussion, broken bone or fracture, or serious cut or puncture within the last 12 months, overall and by sex and age group. Head injuries and concussions (4.0%) were the most commonly reported, but the least likely to be seen by a medical professional. Injuries most frequently occurred while engaging in sports, physical activity or playing.

Overall, head injuries or concussions were the most commonly reported injury (4.0%), among the types of injuries surveyed. Serious cuts and punctures were most common among young children (aged 1 to 4 years), fractures were most common among children aged 10 to 14 years and head injuries or concussions were most common in youth aged 15 to 17 years. The most common activities that children and youth were partaking in when the injury occurred were playing and engaging in sports or physical activity. The majority of self-reported injuries led to a consultation.

Dans l'ensemble, les traumatismes crâniens ou les commotions c érébrales ont constitué les blessures les plus fréquemment déclarées (4,0 %) parmi les types de blessures recensées. Les blessures les plus fréquentes étaient les coupures et les perforations graves chez les jeunes enfants de 1 à 4 ans, les fractures chez les 10 à 14 ans, et les traumatismes crâniens et commotions cérébrale s chez les jeunes de 15 à17 ans,. Les activités les plus courantes auxquelles s'adonnaient les enfants et les jeunes au moment de la blessure étaient le jeu, le sport ou l'activité physique. La majorité des blessures autodéclarées ont mené à la consultation d'un professionnel de la santé.

Investigating the Effect of Return-to-Play Timing After Injury on Performance: Does the Analysis Answer the Research Objective?

Return-to-play decision making should be based on all the advantages and disadvantages of return to play for athletes, not just the risk of injury. For competitive athletes, this includes the effect of early versus delayed return to sport on performance. In this paper, we address the questions "How can I estimate the effect of injury on the individual's performance at return to play?" and "What is the effect of delaying return to sport on the individual's performance?". To address these questions, we describe (1) some foundational concepts, design and analytical challenges related to estimating the causal effect of return to play timing on performance in the athlete, (2) additional challenges if one is interested in the effects of delaying return to play and (3) differences when the questions relate to the team's performance. Although the analytical strategies described appear complicated, coaches and athletes make these judgements informally every day without explicitly stating their assumptions. Using a formal approach should help analysts provide the most valid answers to the questions asked by athletes and coaches. In brief, the choice of a comparison group depends on the research question and requires that one consider the hypothetical performance trajectory of the athlete had they never been injured. Thus, the optimal comparison group depends on the shape of the expected trajectory and the specific research question being asked.

Investigating the association between sleep and aspects of mental health in children: findings from the Canadian Health Survey on Children and Youth. / Étude de l'association entre sommeil et composantes de la santé mentale des enfants : résultats de l'Enquête canadienne sur la santé des enfants et des jeunes.

INTRODUCTION: Sufficient sleep and good quality sleep are crucial aspects of children's healthy development. While previous research has suggested associations between sleep and positive mental health, few studies have been conducted in Canadian children. METHODS: This study used data from the 2019 Canadian Health Survey on Children and Youth. Parents of children aged 5 to 11 years (N = 16 170) reported on their children's sleep habits and mental health. Descriptive statistics were used to calculate means and percentages for sleep and mental health indicators. Logistic regression was used to compare mental health outcomes by meeting sleep duration recommendations (9-11 hours of sleep vs. < 9 or > 11 hours of sleep), sleep quality (difficulties getting to sleep) and having enforced rules for bedtime. RESULTS: Overall, 86.2% of children aged 5 to 11 years met sleep duration recommendations (9-11 hours of sleep), 90.0% had high sleep quality and 83.1% had enforced rules for bedtime. While 83.0% of children had high general mental health, mental health diagnoses were reported for 9.5% of children, and 15.8% of children required or received mental health care. High sleep quality was consistently associated with better mental health, enforced rules for bedtime were associated with some negative mental health outcomes and meeting sleep duration recommendations tended not to be associated with mental health outcomes. CONCLUSION: Sleep quality was strongly associated with mental health among children in this study. Future research should explore longitudinal associations between sleep and mental health in Canadian children.

INTRODUCTION: Un sommeil suffisant et un sommeil de bonne qualité sont des composantes cruciales du développement sain des enfants. Si des recherches antérieures laissent entrevoir des associations entre le sommeil et une bonne santé mentale, peu d'études ont été menées chez les enfants canadiens. MÉTHODOLOGIE: Cette étude se fonde sur les données de l'Enquête canadienne sur la santé des enfants et des jeunes de 2019. Des parents d'enfants âgés de 5 à 11 ans (N = 16 170) ont fait état des habitudes de sommeil et de la santé mentale de leurs enfants. Des statistiques descriptives ont servi à calculer les moyennes et les pourcentages des indicateurs du sommeil et de la santé mentale. Une régression logistique a été utilisée pour comparer les résultats en matière de santé mentale en fonction du respect des recommandations sur la durée du sommeil (9 à 11 heures de sommeil contre moins de 9 heures ou plus de 11 heures), la qualité du sommeil (difficulté à s'endormir) et l'application de règles relatives à l'heure du coucher. RÉSULTATS: Dans l'ensemble, 86,2 % des enfants de 5 à 11 ans respectaient les recommandations sur la durée du sommeil (9 à 11 heures de sommeil), 90,0 % avaient un sommeil de grande qualité et 83,1 % avaient des règles à respecter concernant l'heure du coucher. Si 83,0 % des enfants avaient un niveau élevé de santé mentale générale, des diagnostics en matière de santé mentale ont tout de même été déclarés pour 9,5 % des enfants, et 15,8 % ont eu besoin de soins de santé mentale ou en ont reçus. Un sommeil de grande qualité a été systématiquement associé à une meilleure santé mentale, l'application de règles relatives à l'heure du coucher a été associée à certains effets négatifs sur la santé mentale et le respect des recommandations sur la durée du sommeil ne semble pas avoir d'incidence sur la santé mentale. CONCLUSION: Cette étude révèle une forte association entre la qualité du sommeil et la santé mentale chez les enfants. Les recherches futures devraient se pencher sur les associations longitudinales entre le sommeil et la santé mentale des enfants canadiens.

No associations between C-reactive protein and spinal pain trajectories in children and adolescents (CHAMPS study-DK).

Preliminary evidence points to a link between C-reactive protein (CRP) and spinal pain in adults. However, there is a paucity of research in younger populations. Therefore, we aimed to determine associations between CRP and spinal pain in childhood and adolescence. We identified trajectories of spinal pain from childhood to adolescence and investigated the associations between CRP and trajectory subgroups. Six- to 11-year-old children from 13 primary schools, were followed from October 2008 and until 2014. High-sensitivity CRP collected at baseline (2008) was measured using serum samples. The outcome was the number of weeks with non-traumatic spinal pain between November 2008 and June 2014. We constructed a trajectory model to identify different spinal pain trajectory subgroups. The associations between CRP and spinal pain trajectory subgroups were modelled using mixed-effects multinominal logistic regression. Data from 1556 participants (52% female), with a mean age of 8.4 years at baseline, identified five spinal pain trajectory subgroups: "no pain" (55.3%), "rare" (23.7%), "rare, increasing" (13.6%), "moderate, increasing" (6.1%), and "early onset, decreasing" (1.3%). There were no differences in baseline high-sensitivity CRP levels between spinal pain trajectory subgroups. Thus, the heterogeneous courses of spinal pain experienced were not defined by differences in CRP at baseline.

Implementing Multiple Imputation for Missing Data in Longitudinal Studies When Models are Not Feasible: An Example Using the Random Hot Deck Approach.

Purpose: Researchers often use model-based multiple imputation to handle missing at random data to minimize bias. However, constraints within the data may sometimes result in implausible values, making model-based imputation infeasible. In these contexts, we illustrate how random hot deck imputation can allow for plausible multiple imputation in longitudinal studies. Patients and Methods: Our motivating example is the Childhood Health, Activity, and Motor Performance School Study Denmark (CHAMPS-DK), a prospective cohort study that measured weekly sports participation for 1700 Danish schoolchildren. Using observed data on 4 variables (pain, activity frequency, sport, sport counts), we created a gold-standard data set without missing data. We then created a synthetic data set by setting some variable values to missing based on a prediction model that mimicked real-data missingness patterns. To create 5 imputed data sets, we matched each record with missing data to several fully observed records, generated probabilities from matched records, and sampled from these records based on the probability of each occurring. We assessed variability and agreement (kappa) between the imputed data sets and the gold-standard data set. We compare results to common model-based imputation methods. Results: Variability across data sets appeared reasonable. The range of kappa for the random hot deck approach was moderate for activity frequency (0.65 to 0.71) and sport (0.59 to 0.85), and poor for common model-based approaches (range 0.00 to 0.11). The range of kappas for sport count was strong (0.87 to 0.97) for random hot deck imputation and weak to moderate (0.55 to 0.71) for common model-based imputation. Agreement was higher when more information was present, and when prevalence was higher for our binary variable sport. Conclusion: Random hot deck imputation should be considered as an alternative method when model-based approaches are infeasible, specifically where there are constraints within and between covariates.

Causal effects, workload and injury risk: The importance of specifying the research question.

OBJECTIVES: To illustrate why the research question determines whether and how sport medicine investigators should adjust for workload when interested in interventions or causal risk factors for injury. DESIGN: Theoretical conceptualization. METHODS: We use current concepts of causal inference to demonstrate the advantages and disadvantages of adjusting for workload through different analytic approaches when evaluating causal effects on injury risk. RESULTS: When a risk factor of interest changes workload, including workload in the regression will cause bias. When workload represents time-at-risk (e.g. games played, minutes run), including workload as an offset in Poisson regression provides a comparison of injury rates (injuries per unit time). This is equivalent to including log(workload) as an independent variable with the coefficient fixed to 1. If workload is included as an independent variable instead of an offset, using log(workload) rather than workload is more consistent with theory. This practice is similar to the principles of allometric scaling. When workload represents a combination of both time-at-risk and intensity, such as with session ratings of perceived exertion, the optimal analytical strategy may require modeling time-at-risk and intensity separately rather than as one factor. CONCLUSIONS: Whether to account for recent workload or not, and how to account for recent workload, depends on the research question and the causal assumptions, both of which should be explicitly stated.

Sleep behaviours among Canadian adults: Findings from the 2020 Canadian Community Health Survey healthy living rapid response module.

INTRODUCTION: The Canadian 24-Hour Movement Guidelines for Adults, released in October 2020, recommend 7 to 9 hours of good-quality sleep for adults aged 18 to 64 and 7 to 8 hours for adults aged 65 and older, on a regular basis, with consistent sleep and wake times for health benefits. This study assesses the sleep behaviours of Canadian adults and how these behaviours align with the recommendations. DATA AND METHODS: This cross-sectional study uses nationally representative data from the 2020 Canadian Community Health Survey healthy living rapid response module (N = 9,248), collected from January to March 2020. Sleep behaviours were self-reported by respondents, and descriptive statistics were used to calculate means or percentages for sleep duration, guideline adherence, physical activity and screen time, sleep timing, and sleep variability in the full sample. This was done by age, sex, household education, household income adequacy and employment status. RESULTS: Mean sleep duration was 7.9 hours for adults aged 18 to 64, with 77% meeting sleep duration recommendations, and 8.1 hours for adults aged 65 and older, with 55% meeting sleep duration recommendations. Among adults aged 18 to 64, 61% reported high sleep quality, compared with 71% among adults aged 65 and older. High sleep variability (≥30-minute difference between work and free days) and poor sleep-facilitating behaviours were prevalent. Adults who reported high sleep quality and high sleep variability were more likely to meet sleep duration recommendations. INTERPRETATION: To maximize health benefits, continued efforts are needed to promote good sleep behaviours among Canadian adults. Device-based measures of sleep could improve surveillance and research.

Spinal pain in childhood: prevalence, trajectories, and diagnoses in children 6 to 17 years of age.

This study aimed to investigate the trajectories of spinal pain frequency from 6 to 17 years of age and describe the prevalence and frequency of spinal pain and related diagnoses in children following different pain trajectories. First through fifth-grade students from 13 primary schools were followed for 5.5 years. Occurrences of spinal pain were reported weekly via text messages. Children reporting spinal pain were physically evaluated and classified using International Classification of Disease criteria. Trajectories of spinal pain frequency were modeled from age 6 to 17 years with latent class growth analysis. We included data from 1556 children (52.4% female, mean (SD) baseline age = 9.1 (1.9) years) and identified 10,554 weeks of spinal pain in 329,756 weeks of observation. Sixty-three percent of children reported one or more occurrences of spinal pain. We identified five trajectories of spinal pain frequency. Half the children (49.8%) were classified as members of a "no pain" trajectory. The remaining children followed "rare" (27.9%), "rare, increasing" (14.5%), "moderate, increasing" (6.5%), or "early-onset, decreasing" (1.3%) spinal pain trajectories. The most common diagnoses in all trajectory groups were non-specific (e.g., "back pain"). Tissue-specific diagnoses (e.g., muscle strain) were less common and pathologies (e.g., fracture) were rare.  Conclusion: From childhood through adolescence, spinal pain was common and followed heterogeneous courses comprising stable, increasing, and early-onset trajectories. These findings accord with recommendations from adult back pain guidelines that most children with spinal pain can be reassured that they do not have a serious disease and encouraged to stay active. What is Known: • Spinal pain imposes a large burden on individuals and society. • Although many people first experience the condition in childhood, little is known about the developmental trajectories of spinal pain from childhood to adolescence. What is New: • Data from 1556 children and 329,756 participant weeks showed five unique spinal pain trajectories from 6 to 17 years: most children rarely reported spinal pain, while one in five followed increasing or early-onset trajectories. • Most pain occurrences were non-specific; pathological diagnoses were rare.

Predicting Injury Risk Over Changes in Physical Activity in Children Using the Acute:Chronic Workload Ratio.

Limited research exists on the relationship between changes in physical activity levels and injury in children. In this study, we investigated the prognostic relationship between changes in activity, measured by the acute:chronic workload ratio (ACWR), and injury in children. We used data from the Childhood Health, Activity, and Motor Performance School Study Denmark (2008-2014), a prospective cohort study of 1,660 children aged 6-17 years. We modeled the relationship between the uncoupled 5-week ACWR and injury, defined as patient-reported musculoskeletal pain, using generalized additive mixed models. These methods accounted for repeated measures, and they improved model fit and precision compared with previous studies that used logistic models. The prognostic model predicted an injury risk of approximately 3% between decreases in activity level of up to 60% and increases of up to 30%. Predicted risk was lower when activity decreased by more than 60% (minimum of 0.5% with no recreational activity). Predicted risk was higher when activity increased by more than 30% (4.5% with a 3-fold increase in activity). Girls were at significantly higher risk of injury than boys. We observed similar patterns but lower absolute risks when we restricted the outcome to clinician-diagnosed injury. Predicted increases in injury risk with increasing activity were much lower than those of previous studies carried out in adults.

Analyzing Activity and Injury: Lessons Learned from the Acute:Chronic Workload Ratio.

Injuries occur when an athlete performs a greater amount of activity than what their body can withstand. To maximize the positive effects of training while avoiding injuries, athletes and coaches need to determine safe activity levels. The International Olympic Committee has recommended using the acute:chronic workload ratio (ACWR) to monitor injury risk and has provided thresholds to minimize risk when designing training programs. However, there are several limitations to the ACWR and how it has been analyzed which impact the validity of current recommendations and should discourage its use. This review aims to discuss previously published and novel challenges with the ACWR, and strategies to improve current analytical methods. In the first part of this review, we discuss challenges inherent to the ACWR. We explain why using a ratio to represent changes in activity may not always be appropriate. We also show that using exponentially weighted moving averages to calculate the ACWR results in an initial load problem, and discuss their inapplicability to sports where athletes taper their activity. In the second part, we discuss challenges with how the ACWR has been implemented. We cover problems with discretization, sparse data, bias in injured athletes, unmeasured and time-varying confounding, and application to subsequent injuries. In the third part, conditional on well-conceived study design, we discuss alternative causal-inference based analytical strategies that may avoid major flaws in studies on changes in activity and injury occurrence.

Effects of shear stress on microalgae - A review.

Cultivation of microalgae requires consideration of shear stress, which is generated by operations such as mixing, circulation, aeration and pumping that are designed to facilitate mass and heat transfer as well as light distribution in cultures. Excessive shear stress can cause increased cell mortality, decreased growth rate and cell viability, or even cell lysis. This review examines the sources of shear stress in different cultivation systems, shear stress tolerance of different microalgal species and the physiological factors and environmental conditions that may affect shear sensitivity, and potential approaches to mitigate the detrimental effects of shear stress. In general, green algae have the greatest tolerance to shear stress, followed by cyanobacteria, haptophytes, red algae, and diatoms, with dinoflagellates comprising the most shear-sensitive species. The shear-sensitivity of microalgae is determined primarily by cell wall strength, cell morphology and the presence of flagella. Turbulence, eddy size, and viscosity are the most prominent parameters affecting shear stress to microalgal cells during cultivation.