Collision activity during training increases total energy expenditure measured via doubly labelled water

When to Pull the Trigger: Conceptual Considerations for Approximating Head Acceleration Events Using Instrumented Mouthguards

Head acceleration events (HAEs) are acceleration responses of the head following external short-duration collisions. The potential risk of brain injury from a single high-magnitude HAE or repeated occurrences makes them a significant concern in sport. Instrumented mouthguards (iMGs) can approximate HAEs. The distinction between sensor acceleration events, the iMG datum for approximating HAEs and HAEs themselves, which have been defined as the in vivo event, is made to highlight limitations of approximating HAEs using iMGs. This article explores the technical limitations of iMGs that constrain the approximation of HAEs and discusses important conceptual considerations for stakeholders interpreting iMG data. The approximation of HAEs by sensor acceleration events is constrained by false positives and false negatives. False positives occur when a sensor acceleration event is recorded despite no (in vivo) HAE occurring, while false negatives occur when a sensor acceleration event is not recorded after an (in vivo) HAE has occurred. Various mechanisms contribute to false positives and false negatives. Video verification and post-processing algorithms offer effective means for eradicating most false positives, but mitigation for false negatives is less comprehensive. Consequently, current iMG research is likely to underestimate HAE exposures, especially at lower magnitudes. Future research should aim to mitigate false negatives, while current iMG datasets should be interpreted with consideration for false negatives when inferring athlete HAE exposure.

The Frequency and Severity of Gastrointestinal Symptoms in Rugby Players

This study aimed to assess the self-reported frequency and severity of gastrointestinal symptoms (GIS) at rest and around rugby training and match play in male and female rugby union players. An online questionnaire was sent to registered rugby union players (sevens or fifteens). Thirteen GIS were assessed alongside perceptions of appetite around rugby and rest using Likert and visual analog scales. Questions investigating a range of medical and dietary factors were included. Three hundred and twenty-five players (male n=271, female n=54) participated in the study. More frequent GIS (at least one GIS experienced weekly/more often) was reported by players at rest (n=203; 62%) compared to around rugby (n=154; 47%). The overall severity of GIS was low (mild discomfort), but a portion of players (33%) did report symptoms of moderate severity around rugby. Female players reported more frequent and severe symptoms compared to male counterparts (p<0.001). Self-reported appetite was significantly lower after matches compared to training. There were no dietary or medical factors associated with GIS severity scores. This study describes GIS characteristics in male and female rugby union players. Half of the players assessed experienced some form of GIS that may affect nutrition, training, or performance, and should thus be a consideration for practitioners supporting this cohort.

The Development of a Resting Metabolic Rate Prediction Equation for Professional Male Rugby Union Players

Determining resting metabolic rate (RMR) is an important aspect when calculating energy requirements for professional rugby union players. Prediction equations are often used for convenience to estimate RMR. However, the accuracy of current prediction equations for professional rugby union players remains unclear. The aims of this study were to examine the RMR of professional male rugby union players compared to nine commonly used prediction equations and develop and validate RMR prediction equations specific to professional male rugby union players. One hundred and eight players (body mass (BM) = 102.9 ± 13.3 kg; fat-free mass (FFM) = 84.8 ± 10.2 kg) undertook Dual-energy X-ray Absorptiometry scans to assess body composition and indirect calorimetry to determine RMR. Mean RMR values of 2585 ± 176 kcal∙day-1 were observed among the group with forwards (2706 ± 94 kcal·day-1), demonstrating significantly (p < 0.01; d = 1.93) higher RMR compared to backs (2465 ± 156 kcal·day-1), which appeared to be due to their higher BM and FFM measures. Compared to the measured RMR for the group, seven of the nine commonly used prediction equations significantly (p < 0.05) under-estimated RMR (-104-346 kcal·day-1), and one equation significantly (p < 0.01) over-estimated RMR (192 kcal·day-1). This led to the development of a new prediction equation using stepwise linear regression, which determined that the strongest predictor of RMR for this group was FFM alone (R2 = 0.70; SEE = 96.65), followed by BM alone (R2 = 0.65; SEE = 104.97). Measuring RMR within a group of professional male rugby union players is important, as current prediction equations may under- or over-estimate RMR. If direct measures of RMR cannot be obtained, we propose the newly developed prediction equations be used to estimate RMR within professional male rugby union players. Otherwise, developing team- and/or group-specific prediction equations is encouraged.

Estimated Energy Expenditures and Energy Intakes of International Female Rugby Sevens Players in Five Days of a Training Camp and Competition Preparation

To understand the energy balance of international female rugby sevens (R7s) players in applied environments, this study estimated the energy intakes (EI) and total daily estimated energy expenditures (TDEE) during a five-day training camp (TRAIN) and phase of competition preparation (COMP) of equal duration. Tri-axial accelerometer devices were worn throughout both scenarios to estimate TDEE, whereas EI was estimated via self-reported food diaries. Energy deficits of -47% (TDEE_TRAIN: 14.6 ± 1.6 MJ·day^-1, EI_TRAIN: 7.7 ± 0.9 MJ·day^-1, p ≤ 0.001, d = 5.1) and -50% (TDEE_COMP: 15.5 ± 1.6 MJ·day^-1, EI_COMP: 7.7 ± 1.0 MJ·day^-1, p ≤ 0.001, d = 5.7) were observed throughout TRAIN (n = 11; age: 25 ± 4 years, height: 170 ± 6 cm, weight: 71 ± 7 kg) and COMP (n = 8; age: 25 ± 3 years, height: 172 ± 5 cm, weight: 72 ± 6 kg), respectively. Carbohydrate intakes were below the lower range of sports nutrition recommendations in both TRAIN (-62%; 2.3 ± 0.3 g·kg^-1 BM, p ≤ 0.001) and COMP (-60%; 2.4 ± 0.5 g·kg^-1 BM, p ≤ 0.001). For protein (TRAIN: 1.7 ± 0.4 g·kg^-1 BM, COMP: 1.5 ± 0.1 g·kg^-1 BM), intakes met the lower range of recommendations. Fat intake exceeded recommendations of the percentage of total EI (COMP: 39 ± 5%). Accordingly, the dietary strategies of international female R7s players may warrant optimization, as carbohydrate and fat intakes were less than optimal when compared to current performance-based sports nutrition guidelines.

Assessment of activity energy expenditure during competitive golf: The effects of bag carrying, electric or manual trolleys

Golf is a sport played around the globe, with an estimated 42.6 million people playing within the United Kingdom and United States of America alone. To date, there is limited data on the energy expenditure of golf. The present study assessed the activity energy expenditure (AEE) of 16 high-standard (handicap under 5) golfers who completed three rounds of competitive golf either carrying the golf bag (BC), using a manual push trolley (MT) or an electric trolley (ET) (Stewart Golf, Gloucester, UK). Prior to each round, participants were fitted with an Actiheart® accelerometer (Camntech, Fenstanton, UK) to estimate AEE, whilst ratings of perceived exertion (RPE) and enjoyment were collected following each round. Data were analysed using a one-way repeated measures ANOVA, with Hedges g effect sizes (ES) calculated. Mean (SD) AEE was 688 ± 213 kcal for BC, 756 ± 210 kcal for MT and 663 ± 218 kcal for ET (p = .05) although these differences were deemed small or less. The ET condition resulted in the lowest mean heart rate, moderate or very large from BC or MT, respectively. There were no significant differences in enjoyment although perceived exertion was lowest in the ET condition. In summary, we report meaningful differences in AEE between the three conditions (p = .05), with perceived exertion and maximum HR being lowest when using the electric trolley. Golf may be considered as an effective intervention to increase step count and improve physical activity levels across the general population regardless of transportation methods of clubs.

A novel application of entropy analysis for assessing changes in movement variability during cumulative tackles in young elite rugby league players

The aim of this study was to identify between-position (forwards vs. backs) differences in movement variability in cumulative tackle events training during both attacking and defensive roles. Eleven elite adolescent male rugby league players volunteered to participate in this study (mean ± SD, age; 18.5 ± 0.5 years, height; 179.5 ± 5.0 cm, body mass; 88.3 ± 13.0 kg). Participants performed a drill encompassing four blocks of six tackling (i.e. tackling an opponent) and six tackled (i.e. being tackled by an opponent while carrying a ball) events (i.e. 48 total tackles) while wearing a micro-technological inertial measurement unit (WIMU, Realtrack Systems, Spain). The acceleration data were used to calculate sample entropy (SampEn) to analyse the movement variability during tackles performance. In tackling actions SampEn showed significant between-position differences in block 1 (p = 0.0001) and block 2 (p = 0.0003). Significant between-block differences were observed in backs (block 1 vs 3, p = 0,0021; and block 1 vs 4, p = 0,0001) but not in forwards. When being tackled, SampEn showed significant between-position differences in block 1 (p = 0.0007) and block 3 (p = 0.0118). Significant between-block differences were only observed for backs in block 1 vs 4 (p = 0,0025). Movement variability shows a progressive reduction with cumulative tackle events, especially in backs and when in the defensive role (tackling). Forwards present lower movement variability values in all blocks, particularly in the first block, both in the attacking and defensive role. Entropy measures can be used by practitioners as an alternative tool to analyse the temporal structure of variability of tackle actions and quantify the load of these actions according to playing position.

Dietary Intakes of Elite Male Professional Rugby Union Players in Catered and Non-Catered Environments

In professional rugby union, it is common for players to switch between catered and non-catered dietary environments throughout a season. However, little is known about the difference in dietary intake between these two settings. Twelve elite male professional rugby union players (28.3 ± 2.9 y, 188.9 ± 9.5 cm, 104.1 ± 13.3 kg) from the New Zealand Super Rugby Championship completed seven-day photographic food diaries with two-way communication during two seven-day competition weeks in both catered and non-catered environments. While no significant differences were observed in relative carbohydrate intake, mean seven-day absolute energy intakes (5210 ± 674 vs. 4341 ± 654 kcal·day^-1), relative protein (2.8 ± 0.3 vs. 2.3 ± 0.3 g·kgBM·day^-1) and relative fat (2.1 ± 0.3 vs. 1.5 ± 0.3 g·kgBM·day^-1) intakes were significantly higher in the catered compared to the non-catered environment (respectively) among forwards (n = 6). Backs (n = 6) presented non-significantly higher energy and macronutrient intakes within a catered compared to a non-catered environment. More similar dietary intakes were observed among backs regardless of the catering environment. Forwards may require more support and/or attention when transitioning between catered and non-catered environments to ensure that recommended dietary intakes are being achieved.

The effect of rugby training on indirect markers of gut permeability and gut damage in academy level rugby players

Purpose

To assess indirect markers of intestinal endothelial cell damage and permeability in academy rugby players in response to rugby training at the beginning and end of preseason.

Methods

Blood and urinary measures (intestinal fatty acid binding protein and lactulose:rhamnose) as measures of gastrointestinal cell damage and permeability were taken at rest and after a standardised collision-based rugby training session in 19 elite male academy rugby players (age: 20 ± 1 years, backs: 89.3 ± 8.4 kg; forwards: 111.8 ± 7.6 kg) at the start of preseason. A subsample (n = 5) repeated the protocol after six weeks of preseason training. Gastrointestinal symptoms (GIS; range of thirteen standard symptoms), aerobic capacity (30–15 intermittent fitness test), and strength (1 repetition maximum) were also measured.

Results

Following the rugby training session at the start of preseason, there was an increase (median; interquartile range) in intestinal fatty acid binding protein (2140; 1260–2730 to 3245; 1985–5143 pg/ml, p = 0.003) and lactulose:rhamnose (0.31; 0.26–0.34 to 0.97; 0.82–1.07, p < 0.001). After six weeks of preseason training players physical qualities improved, and the same trends in blood and urinary measures were observed within the subsample. Overall, the frequency and severity of GIS were low and not correlated to markers of endothelial damage.

Conclusions

Rugby training resulted in increased intestinal endothelial cell damage and permeability compared to rest. A similar magnitude of effect was observed after six weeks of pre-season training. This was not related to the experience of GIS.

A systematic review: Role of dietary supplements on markers of exercise-associated gut damage and permeability

Nutrition strategies and supplements may have a role to play in diminishing exercise associated gastrointestinal cell damage and permeability. The aim of this systematic review was to determine the influence of dietary supplements on markers of exercise-induced gut endothelial cell damage and/or permeability. Five databases were searched through to February 2021. Studies were selected that evaluated indirect markers of gut endothelial cell damage and permeability in response to exercise with and without a specified supplement, including with and without water. Acute and chronic supplementation protocols were included. Twenty-seven studies were included. The studies investigated a wide range of supplements including bovine colostrum, glutamine, probiotics, supplemental carbohydrate and protein, nitrate or nitrate precursors and water across a variety of endurance exercise protocols. The majority of studies using bovine colostrum and glutamine demonstrated a reduction in selected markers of gut cell damage and permeability compared to placebo conditions. Carbohydrate intake before and during exercise and maintaining euhydration may partially mitigate gut damage and permeability but coincide with other performance nutrition strategies. Single strain probiotic strains showed some positive findings, but the results are likely strain, dosage and duration specific. Bovine colostrum, glutamine, carbohydrate supplementation and maintaining euhydration may reduce exercise-associated endothelial damage and improve gut permeability. In spite of a large heterogeneity across the selected studies, appropriate inclusion of different nutrition strategies could mitigate the initial phases of gastrointestinal cell disturbances in athletes associated with exercise. However, research is needed to clarify if this will contribute to improved athlete gastrointestinal and performance outcomes.

The Effect of Rugby Union Match Play on Sleep Patterns and Subsequent Impact on Postmatch Fatigue Responses

PURPOSE

Sleep is recognized as an important recovery strategy, yet little is known regarding its impact on postmatch fatigue. The aims of this study were to (1) describe sleep and postmatch fatigue, (2) understand how sleep is affected by contextual and match factors, and (3) assess how changes in sleep can affect postmatch fatigue.

METHODS

Twenty-three male rugby union players were monitored across 1 season (N = 71 player-match observations). Actigraphy was used during preseason to establish baseline sleep quality and quantity. Sleep was then measured 1 and 2 days after each match day (MD + 1 and MD + 2). Global positioning systems, notational analysis, and rating of perceived exertion represented external and internal load from matches. Subjective wellness and a standardized run were used to characterize postmatch fatigue 2 days prior (baseline) and at MD + 1 and MD + 2. Linear mixed models established the magnitude of change (effect size [ES]) between baseline, MD + 1, and MD + 2 for sleep and postmatch fatigue. Stepwise forward selection analysis ascertained the effect of match load on sleep and the effect of sleep on postmatch fatigue. Each analysis was combined with magnitude-based decisions.

RESULTS

Sleep characteristics and neuromuscular and perceptual postmatch fatigue were negatively affected at MD + 1 and MD + 2 (ES = small to very large). Kickoff and travel time had the greatest effect on sleep (ES = small). Wellness and soreness were influenced by sleep (fall-asleep time and fragmentation index) and collisions, respectively (ES = small).

CONCLUSION

Sleep quality and quantity were affected independently of the match load (ie, running activity) sustained, and changes in sleep marginally affected postmatch fatigue.

Quantifying Fatigue in the Rugby Codes: The Interplay Between Collision Characteristics and Neuromuscular Performance, Biochemical Measures, and Self-Reported Assessments of Fatigue

Locomotor and collision actions that rugby players complete during match-play often lead to substantial fatigue, and in turn, delays in recovery. The methods used to quantify post-match fatigue and recovery can be categorised as subjective and objective, with match-related collision characteristics thought to have a primary role in modulating these recovery measures. The aim of this review was to (1) evaluate how post-match recovery has been quantified in the rugby football codes (i.e., rugby league, rugby union, and rugby sevens), (2) to explore the time-course of commonly used measures of fatigue post-match, and (3) to investigate the relationships between game-related collisions and fatigue metrics. The available evidence suggests that upper-, and lower-body neuromuscular performance are negatively affected, and biomarkers of muscular damage and inflammation increase in the hours and days following match-play, with the largest differences being at 12–36 h post-match. The magnitude of such responses varies within and between neuromuscular performance (Δ ≤ 36%, n = 13 studies) and tissue biomarker (Δ ≤ 585%, n = 18 studies) measures, but nevertheless appears strongly related to collision frequency and intensity. Likewise, the increase in perceived soreness in the hours and days post-match strongly correlate to collision characteristics across the rugby football codes. Within these findings, there are specific differences in positional groups and recovery trajectories between the codes which relate to athlete characteristics, and/or locomotor and collision characteristics. Finally, based on these findings, we offer a conceptual model of fatigue which details the multidimensional latent structure of the load to fatigue relationship contextualised to rugby. Research to date has been limited to univariate associations to explore relationships between collision characteristics and recovery, and multivariate methods are necessary and recommended to account for the latent structures of match-play external load and post-match fatigue constructs. Practitioners should be aware of the typical time windows of fatigue recovery and utilise both subjective and objective metrics to holistically quantify post-match recovery in rugby.

"Fuel for the Damage Induced": Untargeted Metabolomics in Elite Rugby Union Match Play

The metabolic perturbations caused by competitive rugby are not well characterized. Our aim is to utilize untargeted metabolomics to develop appropriate interventions, based on the metabolic fluctuations that occur in response to this collision-based team sport. Seven members of an English Premiership rugby squad consented to provide blood, urine, and saliva samples daily, over a competitive week including gameday (GD), with physical demands and dietary intake also recorded. Sample collection, processing and statistical analysis were performed in accordance with best practice set out by the metabolomics standards initiative employing 700 MHz NMR spectroscopy. Univariate and multivariate statistical analysis were employed to reveal the acute energy needs of this high intensity sport are met via glycolysis, the TCA cycle and gluconeogenesis. The recovery period after cessation of match play and prior to training recommencing sees a re-entry to gluconeogenesis, coupled with markers of oxidative stress, structural protein degradation, and reduced fatty acid metabolism. This novel insight leads us to propose that effective recovery from muscle damaging collisions is dependent upon the availability of glucose. An adjustment in the periodisation of carbohydrate to increase GD+1 provision may prevent the oxidation of amino acids which may also be crucial to allay markers of structural tissue degradation. Should we expand the ‘Fuel for the work required’ paradigm in collision-based team sports to include ‘Fuel for the damage induced’?

Latent variable dose-response modelling of external training load measures and musculoskeletal responses in elite rugby league players

Establishing dose-response relationships between training load and fatigue can help the planning of training. The aim was to establish the relative importance of external training load measurements to relate to the musculoskeletal response on a group and individual player level. Sixteen elite male rugby league players were monitored across three seasons. Two- to seven-day exponential weighted averages (EWMA) were calculated for total distance, and individualised speed thresholds (via 30-15 Intermittent Fitness Test) derived from global positioning systems. The sit and reach, dorsiflexion lunge, and adductor squeeze tests represented the musculoskeletal response. Partial least squares and repeated measures correlation analyses established the relative importance of training load measures and then investigated their relationship to the collective musculoskeletal response for individual players through the construction of latent variables. On a group level, 2- and 3-day EWMA total distance had the highest relative importance to the collective musculoskeletal response (p < 0.0001). However, the magnitude of relationships on a group (r value = 0.20) and individual (r value = 0.06) level were trivial to small. The lack of variability in the musculoskeletal response over time suggest practitioners adopting such measures to understand acute musculoskeletal fatigue responses should do so with caution.

Physical characteristics of different professional rugby union competition levels

OBJECTIVES

To evaluate whether differences in physical characteristics (running-related and collision-related metrics) exist between four different professional rugby union competition levels.

DESIGN

We collected and retrospectively analysed microsensor technology data from players of two professional rugby union clubs that competed across four different competition levels: International rugby union, European Rugby Champions Cup, PRO14 club competition, and British and Irish Cup.

METHODS

Differences between competition levels were analysed using a one-way ANOVA test. The Tukey HSD test was completed to perform multiple pairwise-comparisons between the means of the competition levels and player positional groups.

RESULTS

Ten of the 12 microsensor technology derived physical characteristics were significantly different between competition levels. Collision load-, collisions-, and high metabolic load efforts-per minute all increased at higher competition levels. These differences were also noted across player positional groups.

CONCLUSIONS

The physical characteristics of rugby union match-play differ across competitions levels. Our data suggest that professional rugby union players require specific physical preparation for different competition levels. In particular, players are likely to need specific preparation and recovery for the higher collision intensity observed at higher competition levels.

Competition Nutrition Practices of Elite Male Professional Rugby Union Players

Thirty-four elite male professional rugby union players from the New Zealand Super Rugby championship completed dietary intakes via the Snap-N-Send method during a seven-day competition week. Mean seven-day absolute energy intake was significantly higher for forwards (4606 ± 719 kcal·day⁻¹) compared to backs (3761 ± 618 kcal·day⁻¹; p < 0.01; d = 1.26). Forwards demonstrated significantly higher mean seven-day absolute macronutrient intakes compared to backs (p < 0.03; d = 0.86–1.58), but no significant differences were observed for mean seven-day relative carbohydrate (3.5 ± 0.8 vs. 3.7 ± 0.7 g·kg·day⁻¹), protein (2.5 ± 0.4 vs. 2.4 ± 0.5 g·kg·day⁻¹), and fat (1.8 ± 0.4 vs. 1.8 ± 0.5 g·kg·day⁻¹) intakes. Both forwards and backs reported their highest energy (5223 ± 864 vs. 4694 ± 784 kcal·day⁻¹) and carbohydrate (4.4 ± 1.2 vs. 5.1 ± 1.0 g·kg·day⁻¹) intakes on game day, with ≈62% of total calories being consumed prior to kick-off. Mean pre-game meal composition for all players was 1.4 ± 0.5 g·kg⁻¹ carbohydrate, 0.8 ± 0.2 g·kg⁻¹ protein, and 0.5 ± 0.2 g·kg⁻¹ fat. Players fell short of daily sports nutrition guidelines for carbohydrate and appeared to “eat to intensity” by increasing or decreasing energy and carbohydrate intake based on the training load. Despite recommendations and continued education, many rugby players select what would be considered a “lower” carbohydrate intake. Although these intakes appear adequate to be a professional RU player, further research is required to determine optimal dietary intakes.

Inside the Belly of a Beast: Individualizing Nutrition for Young, Professional Male Rugby League Players: A Review

Professional rugby league (RL) football is a contact sport involving repeated collisions and high-intensity efforts; both training and competition involve high energy expenditure. The present review summarizes and critiques the available literature relating the physiological demands of RL to nutritional requirements and considers potential ergogenic supplements that could improve players' physical capacity, health, and recovery during the preparatory and competition phases of a season. Although there may not be enough data to provide RL-specific recommendations, the available data suggest that players may require approximately 6-8 g·kg-1·day-1 carbohydrate, 1.6-2.6 g·kg-1·day-1 protein, and 0.7-2.2 g·kg-1·day-1 fat, provided that the latter also falls within 20-35% of total energy intake. Competition nutrition should maximize glycogen availability by consuming 1-4 g/kg carbohydrate (∼80-320 g) plus 0.25 g/kg (∼20-30 g) protein, 1-4 hr preexercise for 80-120 kg players. Carbohydrate intakes of approximately 80-180 g (1.0-1.5 g/kg) plus 20-67 g protein (0.25-0.55 g/kg) 0-2 hr postexercise will optimize glycogen resynthesis and muscle protein synthesis. Supplements that potentially improve performance, recovery, and adaptation include low to moderate dosages of caffeine (3-6 mg/kg) and ∼300 mg polyphenols consumed ∼1 hr preexercise, creatine monohydrate "loading" (0.3 g·kg-1·day-1) and/or maintenance (3-5 g/day), and beta-alanine (65-80 mg·kg-1·day-1). Future research should quantify energy expenditures in young, professional male RL players before constructing recommendations.

Illness and infection in elite full-contact football-code sports: A systematic review

OBJECTIVES

Full-contact football-code team sports offer a unique environment for illness risk. During training and match-play, players are exposed to high-intensity collisions which may result in skin-on-skin abrasions and transfer of bodily fluids. Understanding the incidence of all illnesses and infections and what impact they cause to time-loss from training and competition is important to improve athlete care within these sports. This review aimed to systematically report, quantify and compare the type, incidence, prevalence and count of illnesses across full-contact football-code team sports.

DESIGN/METHODS

A systematic search of Cochrane Library, MEDLINE, SPORTDiscus, PsycINFO and CINAHL electronic databases was performed from inception to October 2019; keywords relating to illness, athletes and epidemiology were used. Studies were excluded if they did not quantify illness or infection, involve elite athletes, investigate full-contact football-code sports or were review articles.

RESULTS

Twenty-eight studies met the eligibility criteria. Five different football-codes were reported: American football (n=10), Australian rules football (n=3), rugby league (n=2), rugby sevens (n=3) and rugby union (n=9). One multi-sport study included both American football and rugby union. Full-contact football-code athletes are most commonly affected by respiratory system illnesses. There is a distinct lack of consensus of illness monitoring methodology.

CONCLUSIONS

Full-contact football-code team sport athletes are most commonly affected by respiratory system illnesses. Due to various monitoring methodologies, illness incidence could only be compared between studies that used matching incidence exposure measures. High-quality illness surveillance data collection is an essential component to undertake effective and targeted illness prevention in athletes.

Body composition differences by age and playing standard in male rugby union and rugby league: A systematic review and meta-analysis

This systematic review and meta-analysis aimed to determine differences in body compositionn between playing standard and age in male rugby union and rugby league athletes. The MOOSE (Meta-analysis of Observational Studies in Epidemiology) guidelines for design, implementation, and reporting were followed. Studies were required to be in male rugby union or league and have body composition as the primary or secondary outcome. Data was required to be presented separately for positional groups and body composition presented as whole-body. A systematic search was performed in PubMed, Cochrane Library, MEDLINE, SPORTDiscus, and CINHAHL via EBSCOhost. 57 studies were included for meta-analysis. Results highlighted significantly higher fat-free mass in senior elite than senior sub-elite or junior elite athletes for all RU and RL forwards. Small and non-significant differences were found in fat mass between rugby union playing standards and age categories. Rugby league senior elite forwards had less fat mass than junior elite forwards. Practitioners should prioritise training and nutritional strategies that maximise fat-free mass development, especially in junior elite cohorts.

Returning to Play after Prolonged Training Restrictions in Professional Collision Sports

The COVID-19 pandemic in 2020 has resulted in widespread training disruption in many sports. Some athletes have access to facilities and equipment, while others have limited or no access, severely limiting their training practices. A primary concern is that the maintenance of key physical qualities (e. g. strength, power, high-speed running ability, acceleration, deceleration and change of direction), game-specific contact skills (e. g. tackling) and decision-making ability, are challenged, impacting performance and injury risk on resumption of training and competition. In extended periods of reduced training, without targeted intervention, changes in body composition and function can be profound. However, there are strategies that can dramatically mitigate potential losses, including resistance training to failure with lighter loads, plyometric training, exposure to high-speed running to ensure appropriate hamstring conditioning, and nutritional intervention. Athletes may require psychological support given the challenges associated with isolation and a change in regular training routine. While training restrictions may result in a decrease in some physical and psychological qualities, athletes can return in a positive state following an enforced period of rest and recovery. On return to training, the focus should be on progression of all aspects of training, taking into account the status of individual athletes.

Can a contemporary dietary assessment tool or wearable technology accurately assess the energy intake of professional young rugby league players? A doubly labelled water validation study

Accurate quantification of energy intake is imperative in athletes; however traditional dietary assessment tools are frequently inaccurate. Therefore, this study investigated the validity of a contemporary dietary assessment tool or wearable technology to determine the total energy intake (TEI) of professional young athletes. The TEI of eight professional young male rugby league players was determined by three methods; Snap-N-Send, SenseWear Armbands (SWA) combined with metabolic power and doubly labelled water (DLW; intake-balance method; criterion) across a combined ten-day pre-season and seven-day in-season period. Changes in fasted body mass were recorded, alongside changes in body composition via isotopic dilution and a validated energy density equation. Energy intake was calculated via the intake-balance method. Snap-N-Send non-significantly over-reported pre-season and in-season energy intake by 0.21 (2.37) MJ^.day^-1 (p = 0.833) and 0.51 (1.73) MJ^.day^-1 (p = 0.464), respectively. This represented a trivial and small standardised mean bias, and very large and large typical error. SenseWear Armbands and metabolic power significantly under-reported pre-season and in-season TEI by 3.51 (2.42) MJ^.day^-1 (p = 0.017) and 2.18 (1.85) MJ^.day^-1 (p = 0.021), respectively. This represents a large and moderate standardised mean bias, and very large and very large typical error. There was a most likely larger daily error reported by SWA and metabolic power than Snap-N-Send across pre-season (3.30 (2.45) MJ^.day^-1; ES = 1.26 ± 0.68; p = 0.014) and in-season periods (1.67 (2.00) MJ^.day^-1; ES = 1.27 ± 0.70; p = 0.012). This study demonstrates the enhanced validity of Snap-N-Send for assessing athlete TEI over combined wearable technology, although caution is required when determining the individual TEIs of athletes via Snap-N-Send.

Development of anthropometric characteristics in professional Rugby League players: Is there too much emphasis on the pre-season period?

Rugby League is a team sport requiring players to experience large impact collisions, thus requiring high amounts of muscle mass. Many players (academy and senior) strive to increase muscle mass during the pre-season, however, quantification of changes during this period have not been thoroughly investigated. We therefore assessed changes in body-composition using Dual X-Ray Absorptiometry (DXA) in eleven academy players over three successive pre-seasons and ninety-three senior players from four different European Super League clubs prior to, and at the end of, a pre-season training period. There was no meaningful change in lean mass of the academy players during any of the pre-season periods (year 1 = 72.3 ± 7.1-73.2 ± 7.2kg; ES 0.05, year 2 = 74.4 ± 6.9-75.5 ± 6.9kg; ES 0.07, year 3 = 75.9 ± 6.7-76.8 ± 6.6kg; ES 0.06) with small changes only occurring over the three-year study period (72.3-75.9kg; ES = 0.22). Senior players showed trivial changes in all characteristics during the pre-season period (total mass = 95.1-95.0kg; ES -0.01, lean mass = 74.6-75.1kg; ES 0.07, fat mass = 13.6-12.9kg; ES -0.17, body fat percentage = 14.8-14.1%; ES -0.19). These data suggest that academy players need time to develop towards profiles congruent with senior players. Moreover, once players reach senior level, body-composition changes are trivial during the pre-season and therefore teams may need to individualise training for players striving to gain muscle mass by reducing other training loads.

There Is Little Difference in the Peak Movement Demands of Professional and Semi-Professional Rugby League Competition

Previous research has quantified the peak movement demands of elite rugby league match-play, but the peak accelerometer load or the semi-professional peak demands remain unknown. The aim of this research was to determine the peak movement demands of professional and semi-professional rugby league competition. Wearable microtechnology devices tracked the physical activity profiles of players during 26 professional (n = 351 files) and 22 semi-professional (n = 267 files) matches. Following each match, data were exported in raw form to extract the peak 1- to 10-min periods for speed, average acceleration, and accelerometer load of each player, using a rolling average method. To determine the difference between playing levels (professional vs. semi-professional) and position (forwards vs. backs), linear mixed models were used. The intercept and the slope were calculated based on the power law relationship to provide the peak, and rate of decay, of each dependent variable. Cohen's effect size (ES) statistic was used to determine the magnitude of differences between positions and playing level. There was little difference between playing standards, with only small differences in running speed, with a greater intercept and slope for the professional forwards compared with semi-professional forwards (intercept ES: 0.37; 90%CL: 0.19 to 0.55; slope ES: 0.35; 0.15 to 0.55). For positional comparisons (forwards vs. backs), there was no difference in running speeds at the professional level, but there was substantially greater running speed for backs compared to forwards in semi-professional competition, with small to moderate differences (ES range: 0.60-0.39). Both professional and semi-professional forwards showed small to moderately higher accelerometer load compared to backs, which increased with period duration (ES range: 0.22-0.79). Similarly, acceleration demands were greater for forwards compared to backs across both playing standards, with moderate to large differences (ES range: 0.52-0.96). Overall, the results of this study show that there is a small difference in the peak running speed for forwards in professional competition, but otherwise there are no meaningful differences in movement demands of professional and semi-professional rugby league match-play. Forwards display greater acceleration and accelerometer load across a number of rolling average durations compared to backs.

Peak movement and collision demands of professional rugby league competition

To quantify the peak movement and contact demands of National Rugby League (NRL) and European Super League (ESL) competition players were tracked during 10 NRL (166 files) and 10 ESL (143 files) matches using microtechnology devices. The peak 1- to 5-min periods were then calculated for average match speed (m·min^-1), and acceleration (m·s^-2) when 0, 1, 2, and ≥3 collisions per min occurred. Linear mixed effect models and Cohen's effect size statistic (± 90%CI) were used to determine the differences in movement profiles when collisions occurred. Compared to no collision periods, as frequency of collisions per minute increased, there were progressive reductions in running speed for most positional groups. The addition of 1 or more collisions per min resulted in average effect size reductions in match speed of -0.14 for NRL forwards, -0.89 for NRL backs, -0.48 for ESL forwards, and -2.41 for ESL backs. ESL forwards had the highest frequency of peak periods involving 3 or more collisions per min, 22% of all periods, followed by NRL forwards (14%), NRL backs (10%) and ESL backs (8%). This study highlights the peak movement and collision demands of professional rugby league competition and allows practitioners to develop training drills that reflect worst case scenarios.

Are professional young rugby league players eating enough? Energy intake, expenditure and balance during a pre-season

Due to the unique energetic demands of professional young collision sport athletes, accurate assessment of energy balance is required. Consequently, this is the first study to simultaneously investigate the energy intake, expenditure and balance of professional young rugby league players across a pre-season period. The total energy expenditure of six professional young male rugby league players was measured via doubly labelled water over a fourteen-day assessment period. Resting metabolic rate was measured and physical activity level calculated. Dietary intake was reported via Snap-N-Send over a non-consecutive ten-day assessment period, alongside changes in fasted body mass and hydration status. Accordingly, energy balance was inferred. The mean (standard deviation) difference between total energy intake (16.73 (1.32) MJ^.day^-1) and total energy expenditure (18.36 (3.05) MJ^.day^-1) measured over the non-consecutive ten-day period was unclear (-1.63 (1.73) MJ^.day^-1; ES = 0.91 ± 1.28; p = 0.221). This corresponded in a most likely trivial decrease in body mass (-0.65 (0.78) kg; ES = 0.04 ± 0.03; p = 0.097). Resting metabolic rate and physical activity level across the fourteen-day pre-season period was 11.20 (2.16) MJ^.day^-1 and 1.7 (0.2), respectively. For the first time, this study utilises gold standard assessment techniques to elucidate the distinctly large energy expenditures of professional young rugby league players across a pre-season period, emphasising a requirement for equally large energy intakes to achieve targeted body mass and composition adaptations. Accordingly, it is imperative that practitioners regularly assess the energy balance of professional young collision-sport athletes to ensure their unique energetic requirements are achieved.

Impact-Induced Muscle Damage: Performance Implications in Response to a Novel Collision Simulator and Associated Timeline of Recovery

The implications of impact-induced muscle damage (IIMD) that results from participation in contact-sport are not well understood. The purpose of the present study was to implement a novel method of generating IIMD and characterise the implications of this on perceptual, biochemical and exercise performance parameters. Eighteen male recreational contact-sport athletes completed a single-group time series with measures assessed at baseline (PRE) and immediately following (POST) an IIMD protocol, with repeat testing 24, 48, and 72 h following the IIMD protocol. Biochemical indices of muscle damage (myoglobin [Mb]) and inflammation (high-sensitivity C-reactive protein [hs-CRP]), 15 m sprint performance, squat jump peak power (SJ-PP), and perceived soreness were compared to PRE using a one-way (time) repeated measures ANOVA with post-hoc t tests. Speed over 5 and 15 m were impaired for 48 h (7.5 ± 4%, p < 0.01) and SJ-PP was impaired for 48 h following the IIMD protocol (9.5 ±3 %, p < 0.01). Subjective soreness was elevated from baseline for 72 h (P < 0.01) following the IIMD protocol. No change in [CRP] or [Mb] was observed (p > 0.01). IIMD resulted in impaired ability to produce power and speed, whilst negatively influencing perceived soreness. These changes were most pronounced in the 48 h following the IIMD protocol. No change in muscle damage or inflammation indices were observed, primarily due to the highly variable response. Thus, the experimental protocol used in the present study may be used as a model to further investigate other aspects of IIMD.