The Relationship Between Training Load and Injury, Illness and Soreness: A Systematic and Literature Review

A Self-Powered Biosensor for Monitoring Maximal Lactate Steady State in Sport Training

A self-powered biosensor for monitoring the maximal lactate steady state (MLSS) during exercise has been developed for intelligently assisting training system. It has been presented to create poly (vinylidene fluoride) (PVDF)/Tetrapod-shaped ZnO (T-ZnO)/enzyme-modified nanocomposite film through an efficient and cost-effective fabrication process. This sensor can be readily attached to the skin surface of the tester. Due to the piezoelectric surface coupling effect, this biosensor can monitor/sense and analyze physical information in real-time under the non-invasive condition and work independently without any battery. By actively outputting piezoelectric signals, it can quickly and sensitively detect body movements (changes of joint angle, frequency relative humidity during exercise) and physiological information (changes of lactate concentration in sweat). A practical application has been demonstrated by an excellent professional speed skater (male). The purpose of this study is to increase the efficiency of MLSS evaluation, promote the development of piezoelectric surface coupling effect and motion monitoring application, develop an intelligently assisting training system, which has opened up a new direction for human motion monitoring.

Internal and External Workload in Youth Basketball Players Who Are Symptomatic and Asymptomatic for Patellar Tendinopathy

OBJECTIVE

To examine the differences in external and internal workload in players with and without patellar tendinopathy.

DESIGN

Nested case-control study.

METHODS

Workload was monitored in 152 players (aged 13-18 years) for a 1-week period, including all practices, games, and conditioning sessions. Players were prescreened into patellar tendinopathy cases and controls without patellar tendinopathy, using the previously validated Oslo Sports Trauma Research Center-patellar tendinopathy questionnaire. Simple linear regression analysis, with adjustment for clustering by team and Bonferroni correction, was used to examine mean differences in measures of external workload (cumulative jump counts and sessions completed) and internal workload (session rating of perceived exertion in arbitrary units) between cases and controls.

RESULTS

A total of 144 players (19 cases, 125 controls) met the inclusion criteria for final analysis. No significant differences were found between players with patellar tendinopathy and those without patellar tendinopathy in the 3 outcomes: jump count (mean difference, 45 jumps; 98.3% confidence interval [CI]: -41, 130; P = .177), basketball sessions completed (mean difference, 0.9; 98.3% CI: -0.3, 2.2; P = .067), and session rating of perceived exertion (mean difference, 346 arbitrary units; 98.3% CI: -459, 1151; P = .260).

CONCLUSION

In the current study, a significant difference in workload was not detected between youth basketball players with patellar tendinopathy and players without patellar tendinopathy. Efforts toward identifying players at early stages of patellar tendinopathy and applying relevant interventions are warranted. J Orthop Sports Phys Ther 2020;50(7):402-408. Epub 6 Sep 2019. doi:10.2519/jospt.2020.9094.

The Impact of Isolation Measures Due to COVID-19 on Energy Intake and Physical Activity Levels in Australian University Students

The coronavirus disease 2019 (COVID-19) pandemic resulted in physical isolation measures in many parts of the world. In Australia, nationwide restrictions included staying at home, unless seeking medical care, providing care, purchasing food, undertaking exercise, or attending work in an essential service. All undergraduate university classes transitioned to online, mostly home-based learning. We, therefore, examined the effect of isolation measures during the early phase of the COVID-19 pandemic in Australia (March/April) on diet (24-h recall) and physical activity (Active Australia Survey) patterns in third-year biomedical students. Findings were compared with students enrolled in the same course in the previous two years. In females, but not males, energy intake was ~20% greater during the pandemic, and snacking frequency and energy density of consumed snacks also increased compared with 2018 and 2019. Physical activity was impacted for both sexes during the pandemic with ~30% fewer students achieving “sufficient” levels of activity, defined by at least 150 min over at least five sessions, compared with the previous two years. In a follow-up study six to eight weeks later (14–18% response rate), during gradual easing of nationwide restrictions albeit continued gym closures and online learning, higher energy intake in females and reduced physical activity levels in both sexes persisted. These data demonstrate the health impacts of isolation measures, with the potential to affect long-term diet and activity behaviours.

Comparison of individual and group-based load-velocity profiling as a means to dictate training load over a 6-week strength and power intervention

This study compared the effects of dictating load using individual (ILVP) or group (GLVP) load-velocity profiles on lower-body strength and power. Nineteen trained males (23.6 ± 3.7 years) completed a back squat one-repetition maximum (1-RM), load-velocity profiling (LVP), and countermovement (CMJ), static-squat (SSJ) and standing-broad (SBJ) jump tests before and after 6 weeks of resistance training. Participants were randomly assigned to an ILVP, or GLVP intervention with intra-session load dictated through real-time velocity monitoring and prediction of current relative performance using either the participant's LVP (ILVP) or a LVP based on all participant data (GLVP). Training resulted in significant increases in back squat 1-RM for the ILVP and GLVP group (p < 0.01; 9.7% and 7.2%, respectively), with no group-by-time interaction identified between training groups (p = 0.06). All jump performance significantly increased for the ILVP group (p < 0.01; CMJ: 6.6%; SSJ: 4.6%; SBJ: 6.7%), with only CMJ and SSJ improving for the GLVP group (p < 0.05; 4.3%). Despite no significant group-by-time interaction across all variables, the ILVP intervention induced a greater magnitude of adaptation when compared to a GLVP approach. Additionally, an individualised approach may lead to greater positive transfer to power-based movements, specifically vertical and horizontal jumps.

Proteomic Profiling and Monitoring of Training Distress and Illness in University Swimmers During a 25-Week Competitive Season

Purpose

To evaluate relationships of proteomics data, athlete-reported illness, athlete training distress (TDS), and coaches’ ratings of distress and performance over the course of the competitive season.

Methods

Thirty-five NCAA Division II swimmers were recruited to the study (male n = 19, female n = 16; age 19.1 ± 1.6 years). Athletes provided fingerprick dried blood spot (DBS) samples, illness symptoms, and TDS every Monday for 19 of 25 weeks in their season. Coaches monitored performance and rated visual signs of distress. DBS samples were analyzed for a targeted panel of 12 immune-related proteins using liquid chromatography/mass spectrometry (LC/MS).

Results

Thirty-two swimmers completed the protocol. The data were grouped in 2–3 weeks segments to facilitate interpretation and analysis of the data. TDS scores varied between athletes, and were highest during the early fall conditioning ramp up period (8.9 ± 1.6 at baseline to a peak of 22.6 ± 2.0). The percent of athletes reporting illness was high throughout the season (50–78%). Analysis of TDS using Principle Component Analysis (PCA) revealed that 40.5% of the variance (PC1) could be attributed to illness prevalence, and TDS scores for the athletes reporting illness and no illness were different across the season (P < 0.001). The coaches’ ratings of swim performance and swimmer’s distress, sex, and racing distance (sprinters, middle distance, long distance) were not correlated with PC1. Linear Discriminant Analysis (LDA) analysis of the data showed a separation of the baseline weeks from exam weeks with or without competitions, and with competitions alone (p < 0.001). Seven of the 12 proteins monitored over the course of training were upregulated, and the addition of the protein data to LDA analysis enhanced the separation between these groups of weeks.

Conclusion

TDS and illness were related in this group of 32 collegiate swimmers throughout the competitive season, and expression of immune proteins improved the statistical separation of baseline weeks from the most stressful weeks. TDS data provided by the swimmers did not match their coaches’ ratings of distress and swim performance. The importance of the immune system in the reaction to internal and external stress in athletes should be an area of further research.

Stress in Academic and Athletic Performance in Collegiate Athletes: A Narrative Review of Sources and Monitoring Strategies

College students are required to manage a variety of stressors related to academic, social, and financial commitments. In addition to the burdens facing most college students, collegiate athletes must devote a substantial amount of time to improving their sporting abilities. The strength and conditioning professional sees the athlete on nearly a daily basis and is able to recognize the changes in performance and behavior an athlete may exhibit as a result of these stressors. As such, the strength and conditioning professional may serve an integral role in the monitoring of these stressors and may be able to alter training programs to improve both performance and wellness. The purpose of this paper is to discuss stressors experienced by collegiate athletes, developing an early detection system through monitoring techniques that identify the detrimental effects of stress, and discuss appropriate stress management strategies for this population.

Analyzing the Seasonal Changes and Relationships in Training Load and Wellness in Elite Volleyball Players

PURPOSE

The purposes of this study were to (1) analyze the variations of acute and chronic training load and well-being measures during 3 periods of the season (early, mid, and end) and (2) test the associations between weekly training load and well-being measures during different periods of the season.

METHODS

Thirteen professional volleyball players from a team competing in the Portuguese Volleyball First Division (age 31.0 [5.0] y) were monitored during an entire season. Weekly acute (wAL) and chronic load (wCL), acute to chronic workload ratio (wACWL), and training monotony (wTM) were calculated during all weeks of the season. The weekly values of muscle soreness (wDOMS), stress (wStress), fatigue (wFatigue), sleep (wSleep), and Hooper index (wHI) were also obtained across the season.

RESULTS

The midseason had meaningfully low values of wAL (-26.9%; effect size [ES]: -1.12) and wCL (-28.0%; ES: -2.81), and greater values of wACWL (+38.9%; ES: 2.81) compared with early season. The wCL (+10.6%; ES: 0.99), wStress (44.6%; ES: 0.87), and wHI (29.0%; ES: 0.62) were meaningfully greater during the end of season than in midseason. Overall, wAL presented very large correlations with wDOMS (r = .80), wSleep (r = .72), and wFatigue (r = .82).

CONCLUSIONS

The results of this study suggest that the load was meaningfully higher during early season; however, stress was higher during the final stages of the season. Overall, it was also found that the acute load is more highly correlated with well-being status and its variations than chronic load or training monotony.

Injuries during transition periods across the year in pre-professional and professional ballet and contemporary dancers: A systematic review and meta-analysis

OBJECTIVE

To consider the association of injuries with transition periods in the dance year, i.e., when dancers return at the start of the year, and when they transition from rehearsal to performance periods.

METHODS

Six electronic databases were searched to November 2019. All English language peer-reviewed studies, of any study design investigating ballet and contemporary pre-professional and professional dance populations were included. Only those studies reporting on the timing of injury were included.

RESULTS

Fifteen cohort and two case-series studies were included. A meta-analysis of seven studies revealed the rate of injuries to be significantly higher for the second and third months (1.52; 95% confidence interval [CI]:1.11-2.08; 1.26; 95%CI:1.07-1.48 respectively) after the return to dance. Two further studies report more injuries up to Week 13 of the year. One study showed an increase in injured dancers at three and four weeks after transition from rehearsals to a performance season. Four studies show an increase in injuries at performance times.

CONCLUSIONS

Meta-analyses of seven studies shows the second and third months after returning to dance have a significantly higher rate of injuries. More research is needed to quantify training loads in dance. Practitioners should be cognisant of the higher injury rates during periods of transition and consider modifying load, as it is a potential contributing factor.

Injury risk and injury incidence rates in CrossFit

INTRODUCTION

Despite completing complex movements under cardiovascular and muscular fatigued conditions, CrossFit suggested safety of participants is one of the most important factors to consider. Therefore, the aim of this brief review was to provide an overview of the injury incidence and incidence rates reported in the current literature as well as to assess the injury risks associated with CrossFit.

EVIDENCE ACQUISITION

Research papers were searched using the following databases: Scopus, SPORTDiscus, Web of Science, PubMed, and MEDLINE. The search identified 718 potential articles across all databases. After the application of inclusion criteria, a total of 14 articles were included in this review.

EVIDENCE SYNTHESIS

The shoulder, spine, and knee are the most commonly injured areas in CrossFit. Injury incidence of each study ranges from 12.8-73.5% and reported injury rates ranging from 0.27-3.3/1000 training hours.

CONCLUSIONS

Reported findings in the current literature would suggest CrossFit has a relatively low injury risk. The current review highlights three important factors associated with injury incidence and incidence rates in CrossFit: 1) training frequency; 2) duration of CrossFit experience; 3) individuals that compete in CrossFit competitions. Due to recall bias and selection bias further research is warranted over a longitudinal prospective study. Additionally, further research is needed to investigate mechanisms of injury and the relationship between training load and injury risk in CrossFit.

Differences in Weekly Load Distribution Over Two Euroleague Seasons with a Different Head Coach

The weekly training management and competition loads are important aspects to optimize the performance of professional basketball players. The objectives of the study were (a) to describe the weekly external load (EL), as well as the internal response (IR), of elite basketball players over two consecutive seasons with a different head coach and (b) to compare weekly loads of different competitive densities. The data were collected from 27 elite players from the same team competing in the Spanish first division league (ACB) and EuroLeague during 2017–2018 and 2018–2019 seasons. EL was measured using microsensor technology to determine PlayerLoad values, expressed in arbitrary units (AU). Session rating of perceived exertion (sRPE) was used for IR quantification. Comparisons between the two seasons and of weeks with different competitive densities were made. The inter-week load variability was moderate-high for both seasons. The highest EL values were measured during the weeks with three games (W3) (W3 > W0 > W2 > W1), while the most demanding week for players’ IR was observed during weeks with no competition (W0). Additionally, higher EL (d = 0.31) and IR (d = 0.37) values were observed in season 2018–2019 compared to 2017–2018. The results obtained in this study contributed new data on the internal and external load required by professional basketball players in weeks with different number of games and showed that different coaching strategies may demand a different external and internal workload in consecutive seasons. Furthermore, the results highlighted the need to carry out an adequate load management program.

'In search of lost time': Identifying the causative role of cumulative competition load and competition time-loss in professional tennis using a structural nested mean model

Injury prevention is critical to the achievement of peak performance in elite sport. For professional tennis players, the topic of injury prevention has gained even greater importance in recent years as multiple of the best male players have been sidelined owing to injury. Identifying potential causative factors of injury is essential for the development of effective prevention strategies, yet such research is hampered by incomplete data, the complexity of injury etiology, and observational study biases. The present study attempts to address these challenges by focusing on competition load and time-loss to competition-a completely observable risk factor and outcome-and using a structural nested mean model (SNMM) to identify the potential causal role of cumulative competition load on the risk of time-loss. Using inverse probability of treatment weights to balance exposure histories with respect to player ability, past injury, and consecutive competition weeks at each time point; the SNMM analysis of 389 professional male players and 55,773 weeks of competition found that total load significantly increases the risk of time-loss (HR = 1.05 per 1,000 games of additional load 95% CI 1.01-1.10) and this effect becomes magnified with age. Standard regression showed a protective effect of load, highlighting the value of more robust causal methods in the study of dynamic exposures and injury in sport and the need for further applications of these methods for understanding how time-loss and injuries of elite athletes might be prevented in the future.

Development of Novel Continuous and Interval Exercise Programs by Applying the FITT-VP Principle in Dogs

Although proper exercise training induces positive physiological effects, improper exercise can lead to injury, fatigue, and poor performance. The frequency, intensity, time/duration, type, volume, and progression (FITT-VP) are the essential components of exercise training to maintain or improve physical fitness and health. The purpose of this study was to develop specific exercise programs by applying the FITT-VP principle and to examine the effects on heart rate (HR) and hematological and biochemical parameters in dogs. The healthy male Beagles (n = 4) included in this study performed continuous and interval exercises, comprising 12 protocols. The HR monitoring elicited an affirmative response to activities but varied depending on the protocols. The hematologic parameters (e.g., red blood cell count, white blood cell count, hemoglobin, mean corpuscular hemoglobin, and mean corpuscular hemoglobin concentration) were within the reference ranges both before and after exercise. The creatine kinase level significantly increased, and the cholesterol level decreased after exercises. In conclusion, the continuous and interval exercise program elicits an appropriate HR reaction, has no adverse effects on the serum parameters, and provides valuable insight for healthcare in dogs.

Workload Monitoring in Team Sports: Using Elite Cricket as an Example

Workload monitoring is used to assess athlete preparedness to ensure that they are optimally prepared for competition. Although many workload studies have been done, most are delimited to individual sport athletes and endurance athletes. There is also controversy regarding which measures and in what combinations they should be used. There is a paucity of literature on workload monitoring in team sports such as cricket. Cricket is an interesting and complex sport which has dimensions of many other sports (team and individual) and was the focus of this broad, narrative review. The review highlights the unique demands of the sport and why consideration of the sport in question is important. It further identifies that most of the workload research has been done on fast bowlers with debate surrounding optimal workloads. It calls for research in specific areas and importantly on other player positions considering their unique demands and identifies what can be used currently by practitioners in the field.

Absolute and Relative Load and Injury in Elite Junior Australian Football Players Over 1 Season

PURPOSE

To investigate the association between training and match loads and injury in elite junior Australian football players over 1 competitive season.

METHODS

Elite junior Australian football players (n = 290, age 17.7 [0.3] y, range 16-18 y) were recruited from the under-18 state league competition in Victoria to report load and injury information. One-week load (session rating of perceived exertion multiplied by duration) and all time-loss injuries were reported using an online sport-injury surveillance system. Absolute load measures (weekly sums) enabled the calculation of relative measures such as the acute:chronic workload ratio. Load measures were modeled against injury outcome (yes/no) using a generalized estimating equation approach, with a 1-wk lag for injury.

RESULTS

Low (<300 arbitrary units [au]) and high (>4650 au) 1-wk loads were associated with significantly higher risk of injury. Furthermore, low (<100 au) and high (>850 au) session loads were associated with a higher risk of injury. High strain values (>13,000) were associated with up to a 5-fold increase in the odds of injury. There was a relatively flat-line association between the acute:chronic workload ratio and injury.

CONCLUSIONS

This study is the first investigation of elite junior athletes demonstrating linear and nonlinear relationships between absolute and relative load measures and injury. Coaches should focus player loads on, or at least close to, the point at which injury risk starts to increase again (2214 au for 1-wk load and 458 au for session load) and use evidence-based strategies across the week and month to help reduce the risk of injury.

Relationship Between Physical Fitness and the Physical Demands of 50-Over Cricket in Fast Bowlers

Webster, TM, Comfort, P, and Jones, PA. Relationship between physical fitness and the physical demands of 50-over cricket in fast bowlers. J Strength Cond Res XX(X): 000-000, 2020-Professional cricket is constantly evolving and resulting in increased physiological demand placed on players. Fast bowlers experience the greatest physical demand during match-play; despite this, research has overlooked the importance of specific physical attributes to optimizing physical match performance. The aim of this study was to investigate the relationships between 50-Over physical match performance and tests of physical qualities in fast bowlers. Fifteen professional male fast bowlers (age = 23.8 ± 4.0 years; height = 183.4 ± 6.7 cm; body mass = 82.9 ± 9.2 kg) participated in the study. Subjects completed the following physical fitness tests; sum of skinfolds, countermovement jump (CMJ), 20-m sprint, and the Yo-Yo intermittent recovery test level 1. Global positioning system data were collected during 6 professional 50-Over fixtures. Moderate correlations were established between CMJ height to total distance covered (r = 0.585; p = 0.022), sprinting distance (ρ = 0.554; p = 0.032), and maximal velocity (r = 0.567; p = 0.027); 20-m sprint time to total distance covered (ρ = -0.519; p = 0.047) and PlayerLoad (ρ = -0.561; p = 0.03); and Yo-Yo distance to total match distance (r = 0.520; p = 0.047) and sprinting distance (ρ = 0.524; p = 0.045). These findings demonstrate the predictive importance of prolonged intermittent running ability, jump, and sprint performance to match running performance of elite fast bowlers in 1-day cricket. Strength and conditioning coaches should use such information to design training to ensure fast bowlers are adequately conditioned to meet the demands of match running performance.

Session Rating of Perceived Exertion as an Efficient Tool for Individualized Resistance Training Progression

Gomes, RL, Lixandrão, ME, Ugrinowitsch, C, Moreira, A, Tricoli, V, and Roschel, H. Session rating of perceived exertion as an efficient tool for individualized resistance training progression. J Strength Cond Res XX(X): 000-000, 2020-The present study aimed to investigate the effects of an individualized resistance training (RT) progression model based on the session rating of perceived exertion (RPE) on gains in muscle mass and strength when compared with a conventional predetermined progression method (PP). Twenty previously trained young male subjects were randomly allocated to 1 of the 2 groups: RPE (n = 10) or PP (n = 10). Muscle cross-sectional area (CSA) and maximum dynamic strength were assessed at baseline and after 6 weeks. The RPE-based progression model resulted in a lower number of high-intensity sessions compared with the PP-based model. Despite this, both groups showed significant and similar increases in CSA (p < 0.0001; RPE = 6.55 ± 5.27% and PP = 9.65 ± 3.63%) and strength (p < 0.0001; RPE = 9.68 ± 4.57% and PP = 9.28 ± 4.01%) after the intervention period. No significant between-group difference was observed for total training volume (RPE = 45,366.00 ± 10,190.00 kg and PP = 47,779.00 ± 5,685.00 kg; p = 0.52). Our results showed that an RT progression model based on session-to-session physiological response assessments resulted in fewer high-intensity training sessions while allowing for similar gains in muscle strength and mass. Thus, trainees are encouraged to adopt session RPE as a potential tool to control workload progression throughout a training period and allowing the optimization of training stimulus on an individual basis.

Seasonal Training Load Quantification and Comparison in College Male Soccer Players

Ryan, GA, Snarr, RL, Eisenman, ML, and Rossi, SJ. Seasonal training load quantification and comparison in college male soccer players. J Strength Cond Res XX(X): 000-000, 2020-Monitoring and quantification of training load (TL) throughout a competitive soccer season is important to ensure players are able to perform throughout the season. The intent of this study was to examine the positional demands and patterns of select measures of TL during a 14-week season in collegiate male soccer players. Heart rate (HR), running performance (SZ), and perceived recovery data were collected daily using a bioharness for each subject (n = 21). Data were grouped into 2- to 3-week training blocks (Pre1, Pre2, In1, In2, In3, and In4). Continuous variables were analyzed using a multivariate analysis of variance, with post hoc Least Squared Difference pairwise comparisons. Significant positional differences were observed across the season. During Pre1, center midfielders (CM) spent more time in %HRlow compared to center backs (CB) (p < 0.01), wide midfielders (p < 0.01), and center forwards (p = 0.04). Center midfielders spent greater time in SZlower than CB (p < 0.01) and wide backs (WB) (p = 0.01). Wide backs spent greater time in SZupper compared to other positions (all p < 0.01). During Pre2, WB spent more time in %HRhigh and SZupper compared to other positions (all p < 0.01). Positional differences were more varied throughout in-season comparisons, but generally, WB and CB demonstrated higher intensities in variables compared to other positions. Tracking variations in positional TLs across the season is important for coaching and training staffs to determine player readiness and plan future training sessions, while helping to mitigate overuse injuries during a long competitive season.

New Wearable Heart Rate Monitor for Contact Sports and Its Potential to Change Training Load Management

Athletes in all sports face injury or illness if they train too much. Therefore, it is crucial for them to manage their training load. Monitoring the heart rate is one way to estimate training load. However, there are limitations to a monitor's measurement ability in contact sports like rugby. Another method to estimate training load in contact sports is the rating of perceived exertion of a player, which is based on a questionnaire. It however takes a long time to obtain answers to questionnaires in team sports. As a solution to this problem, we developed a wearable heart rate monitor for rugby players. The garment-type monitor with flank electrodes can measure the heart rate even in rugby training situations. We also propose a method to estimate the training load from the measured heart rate. The method can be used instead of a questionnaire administered to the players and can reduce the labor in the estimation of the training load.

Influence of Immune and Nutritional Biomarkers on Illness Risk During Interval Training

Intensive training periods may negatively influence immune function, but the immunological consequences of specific high-intensity-training (HIT) prescriptions are not well defined.

PURPOSE

To explore whether 3 different HIT prescriptions influence multiple health-related biomarkers and whether biomarker responses to HIT were associated with upper-respiratory-illness (URI) risk.

METHODS

Twenty-five male cyclists and triathletes were randomized to 3 HIT groups and completed 12 HIT sessions over 4 wk. Peak oxygen consumption (V˙O2peak) was determined using an incremental cycling protocol, while resting serum biomarkers (cortisol, testosterone, 25[OH]D, and ferritin), salivary immunoglobulin-A (s-IgA), and energy availability (EA) were assessed before and after the training intervention. Participants self-reported upper-respiratory symptoms during the intervention, and episodes of URI were identified retrospectively.

RESULTS

Fourteen athletes reported URIs, but there were no differences in incidence, duration, or severity between groups. Increased risk of URI was associated with higher s-IgA secretion rates (odds ratio = 0.90, 90% confidence interval 0.83-0.97). Lower preintervention cortisol and higher EA predicted a 4% increase in URI duration. Participants with higher V˙O2peak reported higher total symptom scores (incidence rate ratio = 1.07, 90% confidence interval 1.01-1.13).

CONCLUSIONS

Although multiple biomarkers were weakly associated with risk of URI, the direction of associations between s-IgA, cortisol, EA, and URI risk were inverse to previous observations and physiological rationale. There was a cluster of URIs in the first week of the training intervention, but no samples were collected at this time point. Future studies should incorporate more-frequent sample time points, especially around the onset of new training regimens, and include athletes with suspected or known nutritional deficiencies.

Modification and Applicability of Questionnaires to Assess the Recovery-Stress State Among Adolescent and Child Athletes

Despite the general consensus regarding the implementation of self-report measures in the training monitoring, there is a lack of research about their applicability and comprehensibility among developing athletes. However, this target group needs special considerations to manage the increasing training demands while maintaining health and performance. This study deals with challenges of applying recovery-stress questionnaires which were validated with adult populations among developing athletes and presents a possible approach to enhance their applicability. In two phases, the Acute Recovery and Stress Scale (ARSS), a 32-adjective list covering eight scales, and the 8-item derived version, the Short Recovery and Stress Scale (SRSS) were answered by 1052 athletes between 10 and 16 years. Phase 1 included 302 14- to 16-year-old athletes who used the original questionnaires with the additional option to mark "I don't understand," while modified versions with additional explanations (phase 2) were applied to 438 adolescents (14.7 ± 0.6 years) and 312 child athletes (11.8 ± 1.1 years). Data of the original validation sample (n = 442) were reanalyzed to examine measurement invariance between adults and adolescents. The results showed comparable psychometric properties to the validation sample (e.g., r it > 0.30) and acceptable fit indices via confirmatory factor analyses (CFA), although more difficulties and limitations were present within the younger groups (e.g., Cronbach's α between 0.50 and 0.87), especially among 10- and 11-year-olds. The original as well as the modified SRSS, on the other hand, indicated good applicability (Cronbach's α between 0.72 and 0.80). Multigroup CFA revealed measurement invariance of the original ARSS among adults and adolescents and of the modified ARSS among adolescents and children. Overall, the present study confirmed the assumption that questionnaires designed by and for adults cannot be directly transferred to younger athletes. The peculiarities and differences in the cognitive and affective development of each age group need to be considered. Future research needs to identify a cut-off age to start the proper use of psychometric tools, especially for state-oriented assessments for routine application in training monitoring. Further modifications and long-term investigations are necessary to implement psychometric monitoring in high-performance environments within youth sport.

The epidemiology of injuries in adult amateur rowers: A cross-sectional study

OBJECTIVES

To investigate the prevalence, nature and factors associated with injury among adult amateur rowers.

DESIGN

Retrospective cross-sectional study.

SETTING

UK-based amateur rowing clubs.

PARTICIPANTS

160 amateur rowers.

MAIN OUTCOME MEASURES

Frequency, type, location, severity and rowing-related factors associated with injury.

RESULTS

Injury rate was 5.7 per 1000 sessions, with no effect of sex (χ² = 0.195, P = 0.659) or weight class (χ² = 0.800, P = 0.371). The lower-back demonstrated an epidemiological incidence proportion (IP) of 0.39 (95%CI = 0.33 to 0.46). The IP for water- and land-based training was 0.39 (95%CI = 0.31 to 0.47) and 0.57 (95%CI = 0.49 to 0.65), respectively. IP was highest between January and March (0.13-0.15), whilst time loss was 0.49 (95%CI = 0.42-0.57). The IP for 'overuse' and 'traumatic' injuries was 0.71 (95%CI = 0.65 to 0.78) and 0.22 (95%CI = 0.16 to 0.27), respectively. Training volume was positively associated with injury rate (r = 0.418, P < 0.001).

CONCLUSIONS

Injury rates appear higher among amateur rowers with the most common injury site being the lower-back. Our results suggest several contextual factors influence injury risk including seasonal phase, training type and training volume.

Robust Exponential Decreasing Index (REDI): adaptive and robust method for computing cumulated workload

Objective

The purpose of this study was to define a new index the Robust Exponential Decreasing Index (REDI), which is capable of an improved analysis of the cumulative workload. This allows for precise control of the decreasing influence of load over time. Additionally, REDI is robust to missing data that are frequently present in sport.

Methods

200 cumulative workloads were simulated in two ways (Gaussian and uniform distributions) to test the robustness and flexibility of the REDI, as compared with classical methods (acute:chronic workload ratio and exponentially weighted moving average). Theoretical properties have been highlighted especially around the decreasing parameter.

Results

The REDI allows practitioners to consistently monitor load with missing data as it remains consistent even when a significant portion of the dataset is absent. Adjusting the decreasing parameter allows practitioners to choose the weight given to each daily workload.

Discussion

Computation of cumulative workload is not easy due to many factors (weekends, international training sessions, national selections and injuries). Several practical and theoretical drawbacks of the existing indices are discussed in the paper, especially in the context of missing data; the REDI aims to settle some of them. The decreasing parameter may be modified according to the studied sport. Further research should focus on methodology around setting this parameter.

Conclusion

The robust and adaptable nature of the REDI is a credible alternative for computing a cumulative workload with decreasing weight over time.

Greater Association of Relative Thresholds Than Absolute Thresholds With Noncontact Lower-Body Injury in Professional Australian Rules Footballers: Implications for Sprint Monitoring

Sprint capacity is an important attribute for team-sport athletes, yet the most appropriate method to analyze it is unclear.

PURPOSE

To examine the relationship between sprint workloads using relative versus absolute thresholds and lower-body soft-tissue and bone-stress injury incidence in professional Australian rules football.

METHODS

Fifty-three professional Australian rules football athletes' noncontact soft-tissue and bone-stress lower-body injuries (N = 62) were recorded, and sprint workloads were quantified over ∼18 months using the global positioning system. Sprint volume (m) and exposures (n) were determined using 2 methods: absolute (>24.9 km·h-1) and relative (≥75%, ≥80%, ≥85%, ≥90%, ≥95% of maximal velocity). Relationships between threshold methods and injury incidence were assessed using logistic generalized additive models. Incidence rate ratios and model performances' area under the curve were reported.

RESULTS

Mean (SD) maximal velocity for the group was 31.5 (1.4), range 28.6 to 34.9 km·h-1. In comparing relative and absolute thresholds, 75% maximal velocity equated to ~1.5 km·h-1 below the absolute speed threshold, while 80% and 85% maximal velocity were 0.1 and 1.7 km·h-1 above the absolute speed threshold, respectively. Model area under the curve ranged from 0.48 to 0.61. Very low and very high cumulative sprint loads ≥80% across a 4-week period, when measured relatively, resulted in higher incidence rate ratios (2.54-3.29), than absolute thresholds (1.18-1.58).

DISCUSSION

Monitoring sprinting volume relative to an athlete's maximal velocity should be incorporated into athlete monitoring systems. Specifically, quantifying the distance covered at >80% maximal velocity will ensure greater accuracy in determining sprint workloads and associated injury risk.

A prospective study of health problems at the 2018 17/U and 19/U Australian National Netball Championships with comparison of surveillance methodology

OBJECTIVE

To investigate the incidence, site, nature and cause of injuries sustained during and four weeks following the 2018 Australian National Netball Championships (ANNC's) using medical attention and self-report surveillance tools.

DESIGN

Prospective cohort study.

METHOD

Injuries were recorded prospectively using medical attention and self-report data collection methods. One hundred and ninety-two athletes competed at the 2018 ANNC's with 96 athletes in each age group (17/U & 19/U).

RESULTS

There were 103 medical attention injuries sustained by 80 athletes resulting in an incidence rate of 89.4 per 1000 player hours. The most frequently recorded medical attention injury diagnoses across both age groups were lateral ankle ligament sprain (n=14, 13.6%), foot blisters (n=11, 10.7%), and lumbar pain (n=10, 9.7%). Ankle sprains (n=4), anterior cruciate ligament (ACL) ruptures (n=3) and concussion (n=3) recorded as the highest sports incapacity injuries. The self-report data collection revealed that 46 (27.2%) athletes arrived at the tournament with an existing self-reported injury/illness and 57 (39.3%) athletes had a self-reported injury/illness at the conclusion of the ANNC (RR 1.44 95%CI 1.05-1.99, p=0.030).

CONCLUSION

There are no recent studies reporting injury rates specifically in pre-elite netball players. This study found an incidence rate of 89.4 per 1000 player hours. Ankle sprains are the highest medical attention and sports-incapacity injury in pre-elite netball athletes. Foot blisters and low back pain also feature in the highest medical attention injuries and ACL rupture and concussion were high sports incapacity injuries at the ANNC's. Finally, combining both the medical attention and self-report injury/illness data collection methods identified more injuries/illnesses than the use of one method alone.

Visualizing the Complexity of the Athlete-Monitoring Cycle Through Principal-Component Analysis

PURPOSE

To discuss the use of principal-component analysis (PCA) as a dimension-reduction and visualization tool to assist in decision making and communication when analyzing complex multivariate data sets associated with the training of athletes.

CONCLUSIONS

Using PCA, it is possible to transform a data matrix into a set of orthogonal composite variables called principal components (PCs), with each PC being a linear weighted combination of the observed variables and with all PCs uncorrelated to each other. The benefit of transforming the data using PCA is that the first few PCs generally capture the majority of the information (ie, variance) contained in the observed data, with the first PC accounting for the highest amount of variance and each subsequent PC capturing less of the total information. Consequently, through PCA, it is possible to visualize complex data sets containing multiple variables on simple 2D scatterplots without any great loss of information, thereby making it much easier to convey complex information to coaches. In the future, athlete-monitoring companies should integrate PCA into their client packages to better support practitioners trying to overcome the challenges associated with multivariate data analysis and interpretation. In the interim, the authors present here an overview of PCA and associated R code to assist practitioners working in the field to integrate PCA into their athlete-monitoring process.

Relationships Between Dry-land Resistance Training and Swim Start Performance and Effects of Such Training on the Swim Start: A Systematic Review

BACKGROUND

The swim start requires an explosive muscular response of the lower body musculature to effectively initiate movement off the starting blocks. There are currently key gaps in the literature evaluating the relationship between dry-land resistance training and swim start performance and the effects of this training on swim start performance, as assessed by the time to 5, 10 or 15 m.

OBJECTIVES

The aims of this systematic review were to critically appraise the current literature on (1) the acute relationship between dry-land resistance training and swim start performance and (2) the acute and chronic effects of dry-land resistance training on swim start performance.

METHODS

An electronic search using AusportMed, Embase, Medline (Ovid), SPORTDiscus and Web of Science was performed. The methodological quality of the studies was evaluated using the Newcastle-Ottawa quality assessment scale (NOS) (cross-sectional studies) and the Physiotherapy Evidence Database (PEDro) scale (intervention studies).

RESULTS

Sixteen studies met the eligibility criteria, although the majority did not utilise the starting blocks or technique currently used in elite swimming. Swim start performance was near perfectly related (r > 0.90) to vertical bodyweight jumps and jump height. Post-activation potentiation and plyometrics were found to produce significant improvements in acute and chronic swim start performance, respectively.

CONCLUSION

While there appears to be strong evidence supporting the use of plyometric exercises such as vertical jumps for monitoring and improving swim start performance, future studies need to replicate these findings using current starting blocks and techniques and compare the chronic effects of a variety of resistance training programmes.

Relationships Between Sport Specialization, Sleep, and Subjective Well-Being in Female Adolescent Athletes

OBJECTIVE

To evaluate the relationship between sport specialization, sleep, and subjective well-being in female youth soccer players.

DESIGN

Prospective cohort study.

SETTING

Community soccer organization.

METHODS

During a 4-month season, 52 female youth soccer players (aged 13-18 years) reported daily training load (TL) and every morning recorded sleep duration and stress, mood, fatigue, soreness, and sleep quality from -3 (worst) to +3 (best). As all the athletes participate in soccer as their primary sport for over 8 months of the year, players were considered specialized if they participated in soccer exclusively and had previously quit another sport to focus on soccer. Least-square mean values from linear mixed effects models were used to compare TL, subjective well-being, and sleep while adjusting for individual repeated measures.

RESULTS

Daily TL during the season did not differ between specialized and nonspecialized athletes (412 ± 24 vs 415 ± 19 arbitrary units, P = 0.96, respectively). Despite similar nightly sleep duration (8.10 ± 0.14 vs 8.25 ± 0.11 hours, P = 0.42), specialized athletes were found to have lower (worse) fatigue (1.02 ± 0.14 vs 1.50 ± 0.11, P = 0.010), soreness (0.66 ± 0.18 vs 1.23 ± 0.14, P = 0.013), mood (1.32 ± 0.12 vs 1.72 ± 0.10, P = 0.013), and sleep quality (1.07 ± 0.13 vs 1.42 ± 0.10, P = 0.035) than the nonspecialized group. Although stress was lower (worse) among the specialized athletes, the difference was not statistically significant (0.97 ± 0.16 vs 1.32 ± 0.13, P = 0.092).

CONCLUSIONS

Among female youth soccer players, sport specialization was associated with impairments in subjective well-being and sleep quality. Additional research is necessary to determine whether this relationship is causal or if factors that influence sport specialization also influence sleep and subjective well-being.

Patellar tendon structure responds to load over a 7-week preseason in elite male volleyball players

The purpose of this study was to investigate the relation between external and internal load and the response of the patellar tendon structure assessed with ultrasound tissue characterization (UTC) in elite male volleyball players during preseason. Eighteen players were followed over 7 weeks, measuring four load parameters during every training and match: volume (minutes played), rating of perceived exertion (RPE) (ranging from 6 to 20), weekly load (RPE*volume), and jump frequency (number of jumps). Patellar tendon structure was measured biweekly using UTC, which quantifies tendon matrix stability resulting in four different echo types (I-IV). On average, players spent 615 min/wk on training and matches with an RPE of 13.9 and a jump frequency of 269. Load evaluation shows significant changes over the 7 weeks: Volume and weekly load parameters were significantly higher in week 3 than week 7 and in week 4 than week 2. Weekly load performed in week 4 was significantly higher than week 7. No significant changes were observed in tendon structure. On the non-dominant side, no significant correlations were found between changes in load parameters and echo types. At the dominant side, a higher weekly volume and weekly load resulted in a decrease of echo type I and a higher mean RPE in an increase of echo type II. The results of this study show that both external and internal load influence changes in patellar tendon structure of elite male volleyball players. Monitoring load and the effect on patellar tendon structure may play an important role in injury prevention.

Sex Differences in Training Loads during British Army Basic Training

PURPOSE

To compare training loads between men and women during 14 wk of British Army standard entry basic training.

METHODS

Thirty-one male (mean ± SD: age, 21 ± 4 yr; height, 1.78 ± 0.08 m; mass, 77.1 ± 10.5 kg) and 28 female (age, 22 ± 4 yr; height, 1.65 ± 0.05 m; mass, 63.9 ± 8.9 kg) British Army recruits had external (distance) and internal (HR, training impulse [TRIMP], RPE) training loads measured during weeks 1, 2, 6, 12, and 13 of basic training. Total energy expenditure was measured during weeks 1 to 2 and weeks 12 to 13.

RESULTS

Daily distance was higher for men than women (13,508 ± 666 vs 11,866 ± 491 m, respectively, P < 0.001). Average daily HR (29% ± 3% vs 30% ± 3% HR reserve) and RPE (4 ± 1 vs 4 ± 1) were not different between men and women, respectively (P ≥ 0.495). Daily TRIMP was higher for women than men (492 ± 130 vs 261 ± 145 au, respectively, P < 0.001). Total energy expenditure was higher for men than women during weeks 1 to 2 (4020 ± 620 vs 2847 ± 323 kcal·d, respectively) and weeks 12 to 13 (4253 ± 556 kcal·d vs 3390 ± 344 kcal·d, respectively) (P < 0.001). Daily RPE, HR, and TRIMP were related to daily distance (R = 0.18-0.57, P ≤ 0.037), and daily RPE was related to daily TRIMP and HR (R = 0.37-0.77, P ≤ 0.001).

CONCLUSIONS

Sex differences in training loads could contribute to the greater injury risk for women during basic training. Daily RPE appears a practical option for measuring internal training load during military training.

Epidemiology of elite sprint kayak injuries: A 3-year prospective study

OBJECTIVES

To analyse the characteristics of injuries sustained by elite sprint kayak athletes, to investigate relationships between initial and subsequent injuries, and to examine injury differences between male and female athletes.

DESIGN

Descriptive epidemiology study.

METHODS

Data from 63 athletes (37 male, 26 female) of the Australian national sprint kayak squad were prospectively collected over three continuous years (September 2014-August 2017). All medical attention injuries were recorded irrespective of time-loss and modality of training. Descriptive analyses were performed, and frequency comparisons across genders assessed with chi squared tests.

RESULTS

Forty-nine athletes (78%) sustained 146 injuries (median=2, interquartile range=1-4, range=0-12). Most injuries were to the upper limb (48%), with the shoulder being the most common body site injured (27%). Thirty-one athletes (49%) sustained at least one subsequent injury, equating to 97 subsequent injuries. The majority (68%) of subsequent injuries occurred at a different site and nature to previous injuries. Male athletes were more likely to sustain an injury than remain injury free compared to female athletes (Chi²₍₁₎=6.75, p=0.009), but there was no difference between males and females who thereafter sustained a subsequent injury (Chi²₍₁₎=0.84, p=0.359).

CONCLUSIONS

Injury occurrence is common in sprint kayak, with many athletes experiencing more than one injury. Small variations in injury characteristics exist between male and female athletes in sprint kayak. This study identifies upper limb and trunk, and joint and muscle injuries as the most prevalent sprint kayak injuries, providing a focus for the development of future injury prevention strategies.

Quantification of a Professional Football Team's External Load Using a Microcycle Structure

Martín-García, A, Gómez Díaz, A, Bradley, PS, Morera, F, and Casamichana, D. Quantification of a professional football team's external load using a microcycle structure. J Strength Cond Res 32(12): 3520-3527, 2018-The aims of this study were to (a) determine the external load of a football team across playing position and relative to competition for a structured microcycle and (b) examine the loading and variation the day after competition for players with or without game time. Training and match data were obtained from 24 professional football players who belonging to the reserve squad of a Spanish La Liga club during the 2015/16 season using global positioning technology (n = 37 matches and n = 42 training weeks). Training load data were analyzed with respect to the number of days before or after a match (match day [MD] minus or plus). Training load metrics declined as competition approached (MD-4 > MD-3 > MD-2 > MD-1; p < 0.05; effect sizes [ES]: 0.4-3.1). On the day after competition, players without game time demonstrated greater load in a compensatory session (MD + 1C) that replicated competition compared with a recovery session (MD + 1R) completed by players with game time (MD + 1C > MD + 1R; p < 0.05; ES: 1.4-1.6). Acceleration and deceleration metrics during training exceeded 50% of that performed in competition for MD + 1C (80-86%), MD-4 (71-72%), MD-3 (62-69%), and MD-2 (56-61%). Full backs performed more high-speed running and sprint distance than other positions at MD-3 and MD-4 (p < 0.05; ES: 0.8-1.7). The coefficient of variation for weekly training sessions ranged from ∼40% for MD-3 and MD-4 to ∼80% for MD + 1R. The data demonstrate that the external load of a structured microcycle varied substantially based on the players training day and position. This information could be useful for applied sports scientists when trying to systematically manage load, particularly compensatory conditioning for players without game time.

Monitoring Training Loads and Perceived Stress in Young Elite University Athletes

With increased professionalism in sport there has been a greater interest in the scientific approach to training and recovery of athletes. Applying appropriate training loads along with adequate recovery, is essential in gaining maximal adaptation in athletes, while minimizing harm such as overreaching, overtraining, injury and illness. Although appropriate physical stress is essential, stress for many athletes may come from areas other than training. Stress from may arise from social or environmental pressure, and for many athletes who combine elite athletic training with university study, academic workloads create significant stress which adds to the constant pressure to perform athletically. This research aimed to determine if subjective stressors were associated with counterproductive training adaptations in university athletes. Moreover, it aimed to elucidate if, and when, such stressors are most harmful (i.e., certain times of the academic year or sports training season). We monitored subjective (mood state, energy levels, academic stress, sleep quality/quantity, muscle soreness, training load) and objective (injury and illness) markers in 182 young (18–22 years) elite athletes over a 4-year period using a commercially available software package. Athletes combined full-time university study with elite sport and training obligations. Results suggest athletes were relatively un-stressed with high levels of energy at the beginning of each university semester, however, energy levels deteriorated along with sleep parameters toward the examination periods of the year. A logistical regression indicated decreased levels of perceived mood (0.89, 0.85–0.94, Odds Ratio and 95% confidence limits), sleep duration (0.94, 0.91–0.97) and increased academic stress (0.91, 0.88–0.94) and energy levels (1.07, 1.01–1.14) were able to predict injury in these athletes. Examination periods coincided with the highest stress levels and increased likelihood of illness. Additionally, a sudden and high increase in training workload during the preseason was associated with an elevated incidence of injury and illness (r = 0.63). In conclusion, young elite athletes undertaking full-time university study alongside their training and competition loads were vulnerable to increased levels of stress at certain periods of the year (pre-season and examination time). Monitoring and understanding these stressors may assist coaches and support staff in managing overall stress in these athletes.

Injury epidemiology and risk factors in competitive artistic gymnasts: a systematic review

Background

Artistic gymnastics is reported to have some of the highest injury rates in sports, which limits participation and often involves considerable medical expenses.

Purpose

To critically appraise the epidemiological literature on injury patterns and risk factors in competitive artistic gymnastics.

Study design

Systematic review.

Methods

Six databases were searched for articles that investigated injuries in competitive artistic gymnasts. Injury incidence, prevalence and risk factor data were extracted, alongside information on injury location, type, severity, nature and mechanism of injury. Quality and level of evidence were assessed using a modified Downs and Black quality index checklist and the Oxford Centre for Evidence-based Medicine guidelines.

Results

The search identified 894 articles, with 22 eligible for inclusion. Descriptive analysis showed that injury incidence and prevalence varied from 0.3 to 3.6 injuries per gymnast (female=0.3–3.6, male=0.7) and 2.0–2.3 (female=2.0–2.3, male=2.0), respectively. Male gymnasts sustained mostly upper limb injuries, while female gymnast reported lower limb injuries. Floor was associated with the greatest number of injuries for both male and female gymnasts. Higher competitive level and exposure to competition were risk factors for gymnastics injury: age, body mass, body size, training duration and life stress were significant associated factors.

Conclusion

Injury incidence and prevalence results are substantial among artistic gymnasts of all competitive levels. Gymnasts who train at highly competitive levels and are exposed to competition environments are a greater risk of injury. Future researchers should implement consistent reporting methods.

Training load and well-being status variations of elite futsal players across a full season: Comparisons between normal and congested weeks

The aim of this study was two-fold: (i) to analyze the variations of internal load (IL) and well-being between normal and congested weeks in professional futsal (also known as indoor soccer) players and (ii) to analyze variations in training days (MD-1, MD-2 and MD-3 [matchday -1, -2, and -3, respectively]) within weeks. Twenty male professional futsal players (age: 27.8 ± 5.7 years old; height: 173.8 ± 5.6 cm; weight: 71.5 ± 7.9 kg) that participated in the first futsal league of Portugal were monitored in all training sessions and matches during a full season. Session ratings of perceived exertion and a Hooper questionnaire (to measure muscle soreness, stress, fatigue, and sleep) were used to monitor the IL and well-being, respectively. Almost certain large decreases in IL during congested weeks in training session MD-3 were observed (-27.7%, [-35.8;-18.6]). Likely moderate decreases in IL during congested weeks in the MD-2 session were also verified (-9.9%, [-17.2;-2.0]). Regarding muscle soreness, almost certain large decreases were found during congested weeks on MD-3 (-21.2%, [-30.0;-11.3]) and MD-1 (-17.3%, [-26.6;-6.9]). Similar evidence was found for fatigue level, as almost certain large decreases were observed during congested weeks on MD-3 (-23.5%, [-32.9;-12.7]) and MD-1 (-16.6%, [-24.8;-7.4]). Within-week changes during normal weeks revealed almost certain large increases in internal load on MD-2 (93.4%, [78.6;109.3]) and MD-3 (106.7%, [88.2;127.0]) in comparison with MD-1. Also, during congested weeks, almost certain large increases of internal load were observed on MD-2 (77.2%, [53.4;104.7]) and MD-3 (65.7%, [42.8;92.3]) in comparison with MD-1. The major findings of this study revealed meaningful increases of IL, muscle soreness, and fatigue in normal weeks in comparison to congested ones. Within-week changes were also observed, with the greatest loads being observed on MD-3 during normal weeks and on MD-2 during congested weeks.

Time-to-event analysis for sports injury research part 1: time-varying exposures

BACKGROUND

'How much change in training load is too much before injury is sustained, among different athletes?' is a key question in sports medicine and sports science. To address this question the investigator/practitioner must analyse exposure variables that change over time, such as change in training load. Very few studies have included time-varying exposures (eg, training load) and time-varying effect-measure modifiers (eg, previous injury, biomechanics, sleep/stress) when studying sports injury aetiology.

AIM

To discuss advanced statistical methods suitable for the complex analysis of time-varying exposures such as changes in training load and injury-related outcomes.

CONTENT

Time-varying exposures and time-varying effect-measure modifiers can be used in time-to-event models to investigate sport injury aetiology. We address four key-questions (i) Does time-to-event modelling allow change in training load to be included as a time-varying exposure for sport injury development? (ii) Why is time-to-event analysis superior to other analytical concepts when analysing training-load related data that changes status over time? (iii) How can researchers include change in training load in a time-to-event analysis? and, (iv) Are researchers able to include other time-varying variables into time-to-event analyses? We emphasise that cleaning datasets, setting up the data, performing analyses with time-varying variables and interpreting the results is time-consuming, and requires dedication. It may need you to ask for assistance from methodological peers as the analytical approaches presented this paper require specialist knowledge and well-honed statistical skills.

CONCLUSION

To increase knowledge about the association between changes in training load and injury, we encourage sports injury researchers to collaborate with statisticians and/or methodological epidemiologists to carefully consider applying time-to-event models to prospective sports injury data. This will ensure appropriate interpretation of time-to-event data.

Training-Monitoring Engagement: An Evidence-Based Approach in Elite Sport

PURPOSE

Poor athlete buy-in and adherence to training-monitoring systems (TMS) can be problematic in elite sport. This is a significant issue, as failure to record, interpret, and respond appropriately to negative changes in athlete well-being and training status may result in undesirable consequences such as maladaptation and/or underperformance. This study examined the perceptions of elite athletes to their TMS and their primary reasons for noncompletion.

METHODS

Nine national-team sprint athletes participated in semistructured interviews on their perceptions of their TMS. Interview data were analyzed qualitatively, based on grounded theory, and TMS adherence information was collected.

RESULTS

Thematic analysis showed that athletes reported their main reason for poor buy-in to TMS was a lack of feedback on their monitoring data from key staff. Furthermore, training modifications made in response to meaningful changes in monitoring data were sometimes perceived to be disproportionate, resulting in dishonest reporting practices.

CONCLUSIONS

Perceptions of opaque or unfair decision making on training-program modifications and insufficient feedback were the primary causes for poor athlete TMS adherence. Supporting TMS implementation with a behavioral-change model that targets problem areas could improve buy-in and enable limited resources to be appropriately directed.

The Current State of Subjective Training Load Monitoring-a Practical Perspective and Call to Action

This commentary delivers a practical perspective on the current state of subjective training load (TL) monitoring, and in particular sessional ratings of perceived exertion, for performance enhancement and injury prevention. Subjective measures may be able to reflect mental fatigue, effort, stress, and motivation. These factors appear to be important moderators of the relationship TL has with performance and injury, and they also seem to differ between open and closed skill sports. As such, mental factors may affect the interaction between TL, performance, and injury in different sports. Further, modeling these interactions may be limited due to the assumption that an independent signal can adequately account for the performance or injury outcomes. An independent signal model does not accurately reflect training environments where multiple stressors (e.g., mechanical, emotional, nutritional) impact adaptations. Common issues with using subjective TL monitoring, including a lack of differentiation between biomechanical, physiological, and cognitive load, may be overcome by considering psychometric measurement best practices, finer graded scales, and differential ratings of perceived exertion. Methods of calculating TL, including different acute and chronic time periods, may also need to be individualized to different sports and potentially different individuals within the same sport. As TL monitoring is predominately a "chronic" decision-making tool, "acute" decision-making tools, e.g., subjective wellness and autonomic nervous system measures, should be combined in a bespoke multivariate model to aid sports coaches. A call to action is presented for future research on key issues associated with TL monitoring that will have relevance for practitioners in an applied setting.

A Narrative Review of the Physical Demands and Injury Incidence in American Football: Application of Current Knowledge and Practices in Workload Management

The sport of American football (AmF) exposes athletes to high-velocity movements and frequent collisions during competition and training, placing them at risk of contact and non-contact injury. Due to the combative nature of the game, the majority of injuries are caused by player contact; however, a significant number are also non-contact soft-tissue injuries. The literature suggests that this mechanism of injury can be prevented through workload monitoring and management. The recent introduction of microtechnology into AmF allows practitioners and coaches to quantify the external workload of training and competition to further understand the demands of the sport. Significant workload differences exist between positions during training and competition; coupling this with large differences in anthropometric and physical characteristics between and within positions suggests that the training response and physiological adaptations will be highly individual. Effective athlete monitoring and management allows practitioners and coaches to identify how athletes are coping with the prescribed training load and, subsequently, if they are prepared for competition. Several evidence-based principles exist that can be adapted and applied to AmF and could decrease the risk of injury and optimise athletic performance.

Training and match volume and injury in adolescents playing multiple contact team sports: A prospective cohort study

Training and competition loads have emerged as valuable injury risk factors but very few studies have explored injury outcomes in adolescent athletes. The aims of this study were to describe injuries and to explore the relationship between training and match load volumes and injury in adolescent athletes participating in multiple contact team sports. One hundred and three male youth rugby athletes aged 14-16 years from 8 rugby union teams were prospectively monitored during a season for weekly training and match volumes and injuries. The relationship between volume and injury was explored by comparing the weekly volume in the week prior to an injury vs weeks without injury. There were 83 time-loss injuries in 58 athletes (62%). Overall injury incidence was 18.5 per 1000 player-hours. Mean weekly injury prevalence was 27% (95% CI 25-30). Average weekly volume was 5.4 (2.2) hours comprising 1.4 (1) match hours and 4 (2.6) training hours. Compared with weeks without injury, weeks prior to an injury had higher match volumes (110 [57] min vs 83 [59] min, P < 0.001). Poisson regression demonstrated that match volume was a predictor of injury with an odds ratio of 1.41 (P = 0.001). The contribution of match volumes to injury risk and the relatively high injury burden in these athletes may be profound. Very high match volumes are unlikely to be in the best interests of young athletes and could be avoided with a systematic approach to load management and athlete development.

The Relationships Between Internal and External Measures of Training Load and Intensity in Team Sports: A Meta-Analysis

BACKGROUND

The associations between internal and external measures of training load and intensity are important in understanding the training process and the validity of specific internal measures.

OBJECTIVES

We aimed to provide meta-analytic estimates of the relationships, as determined by a correlation coefficient, between internal and external measures of load and intensity during team-sport training and competition. A further aim was to examine the moderating effects of training mode on these relationships.

METHODS

We searched six electronic databases (Scopus, Web of Science, PubMed, MEDLINE, SPORTDiscus, CINAHL) for original research articles published up to September 2017. A Boolean search phrase was created to include search terms relevant to team-sport athletes (population; 37 keywords), internal load (dependent variable; 35 keywords), and external load (independent variable; 81 keywords). Articles were considered for meta-analysis when a correlation coefficient describing the association between at least one internal and one external measure of session load or intensity, measured in the time or frequency domain, was obtained from team-sport athletes during normal training or match-play (i.e., unstructured observational study). The final data sample included 122 estimates from 13 independent studies describing 15 unique relationships between three internal and nine external measures of load and intensity. This sample included 295 athletes and 10,418 individual session observations. Internal measures were session ratings of perceived exertion (sRPE), sRPE training load (sRPE-TL), and heart-rate-derived training impulse (TRIMP). External measures were total distance (TD), the distance covered at high and very high speeds (HSRD ≥ 13.1-15.0 km h^-1 and VHSRD ≥ 16.9-19.8 km h^-1, respectively), accelerometer load (AL), and the number of sustained impacts (Impacts > 2-5 G). Distinct training modes were identified as either mixed (reference condition), skills, metabolic, or neuromuscular. Separate random effects meta-analyses were conducted for each dataset (n = 15) to determine the pooled relationships between internal and external measures of load and intensity. The moderating effects of training mode were examined using random-effects meta-regression for datasets with at least ten estimates (n = 4). Magnitude-based inferences were used to interpret analyses outcomes.

RESULTS

During all training modes combined, the external load relationships for sRPE-TL were possibly very large with TD [r = 0.79; 90% confidence interval (CI) 0.74 to 0.83], possibly large with AL (r = 0.63; 90% CI 0.54 to 0.70) and Impacts (r = 0.57; 90% CI 0.47 to 0.64), and likely moderate with HSRD (r = 0.47; 90% CI 0.32 to 0.59). The relationship between TRIMP and AL was possibly large (r = 0.54; 90% CI 0.40 to 0.66). All other relationships were unclear or not possible to infer (r range 0.17-0.74, n = 10 datasets). Between-estimate heterogeneity [standard deviations (SDs) representing unexplained variation; τ] in the pooled internal-external relationships were trivial to extremely large for sRPE (τ range = 0.00-0.47), small to large for sRPE-TL (τ range = 0.07-0.31), and trivial to moderate for TRIMP (τ range= 0.00-0.17). The internal-external load relationships during mixed training were possibly very large for sRPE-TL with TD (r = 0.82; 90% CI 0.75 to 0.87) and AL (r = 0.81; 90% CI 0.74 to 0.86), and TRIMP with AL (r = 0.72; 90% CI 0.55 to 0.84), and possibly large for sRPE-TL with HSRD (r = 0.65; 90% CI 0.44 to 0.80). A reduction in these correlation magnitudes was evident for all other training modes (range of the change in r when compared with mixed training - 0.08 to - 0.58), with these differences being unclear to possibly large. Training mode explained 24-100% of the between-estimate variance in the internal-external load relationships.

CONCLUSION

Measures of internal load derived from perceived exertion and heart rate show consistently positive associations with running- and accelerometer-derived external loads and intensity during team-sport training and competition, but the magnitude and uncertainty of these relationships are measure and training mode dependent.

An Updated Subsequent Injury Categorisation Model (SIC-2.0): Data-Driven Categorisation of Subsequent Injuries in Sport

BACKGROUND

Accounting for subsequent injuries is critical for sports injury epidemiology. The subsequent injury categorisation (SIC-1.0) model was developed to create a framework for accurate categorisation of subsequent injuries but its operationalisation has been challenging.

OBJECTIVES

The objective of this study was to update the subsequent injury categorisation (SIC-1.0 to SIC-2.0) model to improve its utility and application to sports injury datasets, and to test its applicability to a sports injury dataset.

METHODS

The SIC-1.0 model was expanded to include two levels of categorisation describing how previous injuries relate to subsequent events. A data-driven classification level was established containing eight discrete injury categories identifiable without clinical input. A sequential classification level that sub-categorised the data-driven categories according to their level of clinical relatedness has 16 distinct subsequent injury types. Manual and automated SIC-2.0 model categorisation were applied to a prospective injury dataset collected for elite rugby sevens players over a 2-year period. Absolute agreement between the two coding methods was assessed.

RESULTS

An automated script for automatic data-driven categorisation and a flowchart for manual coding were developed for the SIC-2.0 model. The SIC-2.0 model was applied to 246 injuries sustained by 55 players (median four injuries, range 1-12), 46 (83.6%) of whom experienced more than one injury. The majority of subsequent injuries (78.7%) were sustained to a different site and were of a different nature. Absolute agreement between the manual coding and automated statistical script category allocation was 100%.

CONCLUSIONS

The updated SIC-2.0 model provides a simple flowchart and automated electronic script to allow both an accurate and efficient method of categorising subsequent injury data in sport.