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

ObjectivesFull-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/methodsA 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.ResultsTwenty-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.ConclusionsFull-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.     

Evaluation of shoulder joint position sense in both asymptomatic and rehabilitated professional rugby players and matched controls

ObjectiveTo assess if joint position sense (JPS) in the shoulder differed between un-injured rugby players, matched control subjects and previously injured rehabilitated rugby players.DesignMixed design.SettingUniversity biomechanics laboratory.Participants15 asymptomatic professional rugby union players, 15 previously injured professional rugby union players, 15 asymptomatic matched non-rugby playing controls had their JPS assessed.Main outcome measuresJPS was assessed using two criterion angles in the 90° shoulder abduction position (45° and 80° external rotation).ResultsThe study found a significant difference between groups in error score (p = 0.02). The testing angle also had a significant effect on error score (p = 0.002), with greater error scores occurring in the mid range position.ConclusionThis study showed rugby players to have better JPS than controls, indicating JPS might not be related to injury risk. Poor JPS appears to be related to injury, players having sustained an injury have decreased JPS despite surgery and/or rehabilitation and returning to sport without incident.     

Incidence,prevalence and consequences of illness in academy rugby league players

ObjectivesTo assess the incidence, prevalence and consequences of illness in one professional academy rugby league club during an in-season period.DesignObservational prospective cohort study.MethodSeventeen male rugby league players (age 17.7 ± 0.7 years, stature 178.8 ± 5.1 cm, body mass 87.2 ± 9.6 kg) completed a weekly self-report illness questionnaire using an amended version of the Oslo Sports Trauma Research Centre (OSTRC) questionnaire on health problems.ResultsA total of 24 new illnesses were reported over the 25-week study period. 65% of players experienced at least one illness during the study. The incidence of illness in this cohort was 14.3 per 1000-player days, with the respiratory system being most commonly affected (n = 15; 62.5%). The average weekly illness prevalence was 10.3%. Time-loss illness incidence was 1.4 per 1000-player days. Loss of body mass and sleep disruptions were the most commonly reported consequences of illness episodes. Mean body mass loss during a period of illness was 2.2 ± 0.6 kg.ConclusionsAcademy rugby league players are most commonly affected by respiratory illness with a total of nineteen training and competition days lost to illness. Associated consequences of illness, such as loss of body mass and sleep disruptions may present a challenge and negatively impact a rugby league player’s development. Appropriate medical provisions should be provided for Academy rugby league players to support them during periods of illness to limit the impact of these consequences.     

Probiotic supplementation elicits favourable changes in muscle soreness and sleep quality in rugby players

Probiotic supplementation may offer team sport athletes a range of benefits beyond the immune and gastrointestinal systems.ObjectivesTo examine the effects of a probiotic formulation on perceptual markers of sleep quality and quantity, and muscle soreness, leg heaviness and motivation in elite rugby union athletes.MethodsA double-blind randomised controlled trial involving 19 elite male rugby athletes was conducted over 17 weeks encompassing both domestic and international competition. Psychometric variables and salivary biomarkers were assessed twice a week. Athletes were assigned either a daily probiotic (Ultrabiotic 60?) and Saccharomyces boulardii (during international competition) or a placebo. Associations between psychometric scores for perceptual and salivary biomarkers of sleep (melatonin) and inflammation C-reactive protein (CRP) were investigated.ResultsMuscle soreness was ～0.5 units lower (F(1, 343) = 42.646, p < 0.0001) and leg heaviness scores ～0.7 units lower (F(1, 334) = 28.990, p < 0.0001) in the probiotic group compared to the placebo group. Across both groups, as self-reported muscle soreness scores and salivary CRP concentrations increased, sleep quantity, quality and motivation scores decreased. Conversely as muscle soreness scores and CRP decreased, sleep quantity and quality, and motivation scores improved.ConclusionsA long-term programme of probiotic supplementation in international-level rugby union players may yield favourable effects on self-reported muscle soreness and sleep quality associated with muscle soreness during training and competitions.     

Identifying risk factors for contact injury in professional rugby league players – Application of a frailty model for recurrent injury

ObjectivesWell-developed physical qualities may protect against contact injuries. However, the potential contribution of physical qualities as risk or protective factors to contact injury risk is yet to be determined for rugby league. This study applied a frailty survival model that accounts for recurrent injury to identify risk factors for all physiotherapist-reported contact injury in professional rugby league players.DesignProspective cohort study.MethodsSixty-six professional rugby league players participated in this three successive year prospective study. At the start of each season, all players underwent measurements of standard anthropometry (height, body mass, and sum of seven skinfolds), speed (10 m and 40 m sprint), muscular strength (1 repetition maximum [RM] bench press, 1RM squat, 1RM weighted chin-ups), power (vertical jump, bench throw, 1RM power clean, jump squat), and endurance (maximum repetition bench press with 60 kg resistance), repeated-sprint ability (12 × 20 m sprints performed on a 20 s cycle), prolonged high-intensity intermittent running ability (8 × 12 s maximal effort shuttles performed on a 48 s cycle), and maximal aerobic power (multi-stage fitness test). Data was used to demonstrate the application of the frailty model extension of the Cox proportional regression model for recurrent events to identify factors associated with a high hazard ratio (HR) of injury.ResultsHeavier (body mass, HR = 2.6, 95% CI = 1.2–5.7), and faster (40 m sprint, HR = 2.1, 95% CI = 1.0–4.2) players, and those with poorly developed prolonged high-intensity intermittent running ability (HR = 2.9, 95% CI = 1.7–5.0) and upper-body strength (chin-up, HR = 2.2, 95% CI = 1.3–3.7) had a higher incidence of contact injuries.ConclusionsThis study demonstrates application of a novel statistical approach for the analysis of injury data that is recurrent in nature. This approach identified that the greater impact forces generated from heavier players with faster speed may result in an increase in recurrent contact injury rates. However, the development of prolonged high-intensity intermittent running ability and upper-body strength and power may assist to reduce the risk of contact injury in professional rugby league players.     

The effect of physical fatigue on tackling technique in Rugby Union

ObjectivesTo measure the change in tackling technique of rugby union players following an acute bout of physically fatiguing exercise.DesignRandomised cross-over study design with a physical fatigue condition and no-physical fatigue condition (control).MethodsNineteen male amateur club rugby union players (n = 19) and a total of 887 tackles were analysed. During each condition, each player performed four sets of six tackles (three dominant and three non-dominant shoulder) on a contact simulator. Between each set of tackles in the physical fatigue condition, players performed the prolonged high-intensity intermittent running ability test. Using video, player's tackling proficiency for each tackle was measured by awarding either one point or zero points depending on whether a particular technique was performed or not. The sum of these points represents player’s tackling proficiency (score out of 9, measured in arbitrary units).ResultsIn the non-dominant shoulder, a difference between fatigue and control was found at set two (Fatigue 7.3 [7.1–7.6] AU vs. Control 7.6 [7.4–7.9] AU, p = 0.06, ES = 0.3 small) and set three (Fatigue 7.3 [7.0–7.5] AU vs. Control 7.7 [7.5–7.9] AU, p = 0.006, ES = 0.5 small). During the control condition, tackling proficiency scores improved from baseline for non-dominant tackles (Baseline 7.4 [7.2–7.6] AU, vs Set two 7.6 [7.4–7.9] AU, p = 0.08 ES = 0.3 small; vs Set three 7.7 [7.5–7.9] AU, p = 0.05, ES = 0.4 small).ConclusionsIn conclusion, this study shows that physical fatigue can potentially affect rugby union players’ tackling technique. Therefore, players should develop technical capacity to resist the effects of physical fatigue during the tackle.     

The relationship between pre-season fitness testing and injury in elite junior Australian football players

ObjectivesAustralian Football (AF) is a collision sport containing high injury rates in junior competition. Successful performance at the elite junior level not only requires superior specific football knowledge and skills, but also well developed fitness qualities. However, no studies have examined the link between physical fitness qualities and injury in AF.DesignProspective cohort.MethodsInjury data were collected through the use of a Player Movement Record (PMR) and a standardized Injury Report Form (IRF). Fitness test data was collected during the pre-season of the 2010 and 2011 seasons.Results382 players consented to participate in the study. The cohort experienced an injury incidence rate of 24.29/standardized club (40 players/club). A faster 5-m sprint was associated with ‘injury status’ (p = 0.016) and a ‘knee’ region (p ≤ 0.001) injury. A faster planned agility score was associated with an increased risk of a ‘hip/groin/thigh’ region (p = 0.010) injury, and specifically a ‘quadriceps strain’ (p = 0.005). A lower 20-m shuttle run was associated with an increased risk of a ‘shin/ankle/foot’ (p = 0.045) injury. Increased injury severity was associated with a higher left foot running vertical jump (VJ) (p = 0.040), and faster 5-m sprint (p = 0.043).ConclusionsLower aerobic endurance, faster 5-m acceleration and greater planned agility were associated with an increased risk of various injury types in elite junior AF players. Furthermore, a higher left foot running VJ and faster 5-m acceleration were associated with injury severity. These results may largely relate to a greater work capacity placing a higher load upon the musculoskeletal system in contact and non-contact situations.     

Humeral torsion and passive shoulder range in elite volleyball players

ObjectivesTo evaluate variations in humeral torsion in elite male volleyball players and determine whether these changes are related to training history, retrospective injury history and volleyball performance.Design and settingCross sectional design.ParticipantsTwenty-four elite male volleyball players.Main outcome measuresHumeral torsion, passive gleno-humeral rotation ranges and the available internal and external rotation from the humeral torsion neutral position of the dominant and non-dominant arm were measured. Training history and retrospective injury status were ascertained from a questionnaire. Performance was assessed by coach perceived spiking ability and peak serve velocity measures.ResultsHumeral torsion angles demonstrated the dominant arm to be on average 9.6° more retroverted than the non-dominant arm (p = 0.00). In the comparison of volleyball players with and without a history of overuse upper limb injury the most significant finding is on the non-dominant side, those with a history of injury had significantly decreased available external rotation from the humeral torsion neutral position (mean difference = ?15.1, p = 0.04). There was an unexpected negative weak relationship between age commenced and decreased humeral retroversion (r = ?0.413, p = 0.045). There did not appear to be any relationship between humeral torsion and performance measures.ConclusionThe dominant arm of elite male volleyball athletes is more retroverted. There was a tendency for stronger findings in the non-dominant arm in volleyball players with retrospective injury history. We were unable to find any significant correlation between humeral torsion angle and performance measures.     

Back squat velocity to assess neuromuscular status of rugby league players following a match

ObjectivesBack squat mean concentric velocity (MV) and countermovement jump (CMJ) performance were examined in sub-elite rugby league players post-match to monitor changes in neuromuscular status (NMS) from baseline. Relationships between changes in back squat MV and CMJ performance variables were used to compare back squat MV to an established method to monitor NMS.DesignLongitudinal observational design.Methods18 male sub-elite rugby league players (mean ± SD, 20.5 ± 2.4 yr; 180.0 ± 6.7 cm; 93.3 ± 11.2 kg) performed 3 repetitions of CMJ and back squat with an individualised, pre-determined load at ?2 h (baseline), +30 min, +24 h, and +48 h in relation to a match. Back squat MV, CMJ height, CMJ peak power, and CMJ peak velocity were measured with a linear position transducer.ResultsSignificant (p < 0.05), small to large decreases (ES = 0.52–1.24) were observed in back squat MV up to +48 h post-match. Significant (p < 0.05), small to moderate decreases (ES = 0.52–0.70) in CMJ height were also observed up to +24 h post-match, returning to baseline at +48 h. CMJ peak power and peak velocity post-match changes were not significant compared to baseline (p > 0.05). Significant positive correlations were found between changes in back squat MV and CMJ height at +30 min (r = 0.59; p = 0.009) and +48 h (r = 0.51; p = 0.03).ConclusionsThese findings suggest back squat MV may be a suitable alternative or addition to CMJ testing for monitoring NMS in rugby league players.     

Nutrient intake,meal timing and sleep in elite male Australian football players

ObjectivesTo investigate the relationship between dietary intake, meal timing and sleep in elite male Australian football players.DesignProspective cohort study.MethodsSleep and dietary intake were assessed in 36 elite male Australian Football League (AFL) players for 10 consecutive days in pre-season. Sleep was examined using wrist activity monitors and sleep diaries. Dietary intake was analysed using the smartphone application MealLogger and FoodWorks. Generalised linear mixed models examined the associations between diet [total daily and evening (>6 pm) energy, protein, carbohydrate, sugar and fat intake] and sleep [total sleep time (TST), sleep efficiency (SE), wake after sleep onset (WASO) and sleep onset latency (SOL)].ResultsTotal daily energy intake (MJ) was associated with a longer WASO [β = 3, 95%CI: 0.2–5; p = 0.03] and SOL [β = 5, 95%CI: 1?9; p = 0.01]. Total daily protein intake (g kg^?1) was associated with longer WASO [β = 4, 95%CI: 0.8?7; p = 0.01] and reduced SE [β = ?0.7 CI: ?1.3 to ?0.2; p = 0.006], while evening protein intake (g kg^?1) was associated with shortened SOL [β = ?2, 95%CI: ?4 to ?0.4), p = 0.02]. Evening sugar intake (g kg^?1) was associated with shorter TST [β = ?5, 95%CI: ?10 to ?0.6; p = 0.03] and WASO [β = ?1, 95%CI: ?2 to ?0.3; p = 0.005]. A longer period between the evening meal consumption and bedtime was associated with a shorter TST [β = ?8, 95%CI: ?16 to ?0.3; p = 0.04].ConclusionsEvening dietary factors, including sugar and protein intake, had the greatest association with sleep in elite male AFL players. Future research manipulating these dietary variables to determine cause and effect relationships, could guide dietary recommendations to improve sleep in athletes.     

Effects of varying training load on heart rate variability and running performance among an Olympic rugby sevens team

Objectives

To evaluate weekly heart rate variability (HRV) responses to varying training load among an Olympic rugby sevens team and to assess whether HRV responses informed on training adaptation.

Training and game loads and injury risk in elite Australian footballers

ObjectivesTo examine the relationship between combined training and game loads and injury risk in elite Australian footballers.DesignProspective cohort study.MethodsForty-six elite Australian footballers (mean ± SD age of 22.2 ± 2.9 y) from one club were involved in a one-season study. Training and game loads (session-RPE multiplied by duration in min) and injuries were recorded each time an athlete exerted an exercise load. Rolling weekly sums and week-to-week changes in load were then modelled against injury data using a logistic regression model. Odds ratios (OR) were reported against a reference group of the lowest training load range.ResultsLarger 1 weekly (>1750 AU, OR = 2.44–3.38), 2 weekly (>4000 AU, OR = 4.74) and previous to current week changes in load (>1250 AU, OR = 2.58) significantly related (p < 0.05) to a larger injury risk throughout the in-season phase. Players with 2–3 and 4–6 years of experience had a significantly lower injury risk compared to 7+ years players (OR = 0.22, OR = 0.28) when the previous to current week change in load was more than 1000 AU. No significant relationships were found between all derived load values and injury risk during the pre-season phase.ConclusionsIn-season, as the amount of 1–2 weekly load or previous to current week increment in load increases, so does the risk of injury in elite Australian footballers. To reduce the risk of injury, derived training and game load values of weekly loads and previous week-to-week load changes should be individually monitored in elite Australian footballers.     

The prognostic value of the hamstring outcome score to predict the risk of hamstring injuries

ObjectivesHamstring injuries are common among soccer players. The hamstring outcome score (HaOS) might be useful to identify amateur players at risk of hamstring injury. Therefore the aims of this study were: To determine the association between the HaOS and prior and new hamstring injuries in amateur soccer players, and to determine the prognostic value of the HaOS for identifying players with or without previous hamstring injuries at risk of future injury.DesignCohort study.MethodsHaOS scores and information about previous injuries were collected at baseline and new injuries were prospectively registered during a cluster-randomized controlled trial involving 400 amateur soccer players. Analysis of variance and t-tests were used to determine the association between the HaOS and previous and new hamstring injury, respectively. Logistic regression analysis indicated the prognostic value of the HaOS for predicting new hamstring injuries.ResultsAnalysis of data of 356 players indicated that lower HaOS scores were associated with more previous hamstring injuries (F = 17.4; p = 0.000) and that players with lower HaOS scores sustained more new hamstring injuries (T = 3.59, df = 67.23, p = 0.001). With a conventional HaOS score cut-off of 80%, logistic regression models yielded a probability of hamstring injuries of 11%, 18%, and 28% for players with 0,1, or 2 hamstring injuries in the previous season, respectively.ConclusionsThe HaOS is associated with previous and future hamstring injury and might be a useful tool to provide players with insight into their risk of sustaining a new hamstring injury risk when used in combination with previous injuries.     

Hip adductor muscle strength is reduced preceding and during the onset of groin pain in elite junior Australian football players

Groin pain is a condition with a high prevalence in young Australian football players. It is considered that early identification of this condition allows for optimal management. Eighty-six players from two elite under-age Australian football sides were screened weekly for hip adductor muscle strength, using a hand-held dynamometer and for the onset of groin pain. The maximum variation in the average hip adductor muscle strength values of the sample was a 2.6% decrease from baseline in week 7 of the study. Twelve players (14% of the sample studied) reported groin pain for two consecutive weeks and were considered to have an onset of groin injury. The mean hip adductor muscle strength of these players was decreased significantly from baseline by an average of 11.75 ± 2.50% at the week of pain onset (F = 264.76 (1,11), p < 0.001), and 5.82 ± 5.16% in the week preceding the onset of pain (F = 14.03 (1,10), p = 0.004). These results confirm that hip adductor muscle strength is decreased both preceding and during the onset of groin injury in elite under-age Australian footballers.     

Movement pattern comparisons in elite (AFL) and sub-elite (WAFL) Australian football games using GPS

This study examined differences in movement patterns between AFL (elite) and WAFL (sub-elite) players using Global Positioning System (GPS) devices. Maximum speed data and totals of high intensity efforts (>15 km h^?1), sprint efforts (>20 km h^?1) and distance covered were collected on 41 players during the 2008 season. Data were expressed per min of game time played, separated into first and second halves, and also into positions, for both elite and sub-elite players. Overall, elite players had higher movement demands, including 9% more distance covered/min (128 ± 12 m min^?1 vs. 117 ± 15 m min^?1; p < 0.01, ES = 0.84), and 21% more high intensity efforts/min (2.9 ± 0.6 vs. 2.4 ± 0.6; p < 0.01, ES = 0.83). Movement demands significantly declined (p < 0.05–0.01) from first to second half, in both competition levels. For both leagues, Small Forwards/Small Backs and Midfield players covered significantly greater (p < 0.05–0.01) total distances and completed more high intensity efforts than other positions. Ruckmen recorded significantly lower (p < 0.05–0.01) movement demands than Small Forwards/Small Backs, Midfielders and Centre Half-Forwards/Centre Half-Backs over most variables. In conclusion, elite players recorded higher overall movement demands than sub-elite players. This information may be useful for coaches and conditioning staff in designing appropriate training drills for specific role requirements of individual players and assist in the progression of players from sub-elite to elite levels of competition.     

Promoting lower extremity strength in elite volleyball players: Effects of two combined training methods

ObjectivesTo compare the impact of short term training with resistance plus plyometric training (RT+P) or electromyostimulation plus plyometric training (EMS+P) on explosive force production in elite volleyball players.DesignSixteen elite volleyball players of the first German division participated in a training study.MethodsThe participants were randomly assigned to either the RT+P training group (n = 8) or the EMS+P training group (n = 8). Both groups participated in a 5-week lower extremity exercise program. Pre and post tests included squat jumps (SJ), countermovement jumps (CMJ), and drop jumps (DJ) on a force plate. The three-step reach height (RH) was assessed using a custom-made vertec apparatus. Fifteen m straight and lateral sprint (S15s and S15l) were assessed using photoelectric cells with interims at 5 m and 10 m.ResultsRT+P training resulted in significant improvements in SJ (+2.3%) and RH (+0.4%) performance. The EMS+P training group showed significant increases in performance of CMJ (+3.8%), DJ (+6.4%), RH (+1.6%), S15l (?3.8%) and after 5 m and 10 m of the S15s (?2.6%; ?0.5%). The comparison of training-induced changes between the two intervention groups revealed significant differences for the SJ (p = 0.023) in favor of RT+P and for the S15s after 5 m (p = 0.006) in favor of EMS+P.ConclusionsThe results indicate that RT+P training is effective in promoting jump performances and EMS+P training increases jump, speed and agility performances of elite volleyball players.     

Perceived exertion responses to wheelchair propulsion differ between novice able-bodied and trained wheelchair sportspeople

ObjectivesTo investigate peripheral (RPE_P) and central (RPE_C) Ratings of Perceived Exertion during wheelchair propulsion in untrained able-bodied (AB) participants, and trained wheelchair rugby athletes with and without cervical spinal cord injury (CSCI).DesignCross-sectional study.Methods38 participants (AB: n = 20; wheelchair rugby athletes with CSCI: n = 9; without CSCI: n = 9) completed an incremental wheelchair propulsion test to exhaustion on a motorised treadmill. Gas exchange measures and heart rate (HR) were collected throughout. RPE_P and RPE_C on the Category Ratio-10 were verbally recorded each minute. Blood lactate concentration ([BLa]) was determined post-test.ResultsBetween 50–100% peak oxygen uptake (V̇O_2peak), RPE_P was greater than RPE_C in AB (p < 0.05), but not in athletes with (p = 0.07) or without (p = 0.16) CSCI. RPE_P was greater in AB compared to players with CSCI (Effect sizes: 1.24–1.62), as were respiratory exchange ratio (1.02 ± 0.10 vs 0.82 ± 0.11, p < 0.05) and [BLa]_peak (7.98 ± 2.53 vs 4.66 ± 1.57 mmol·L⁻¹). RPE_C was greater in athletes without CSCI compared to those with CSCI (Effect sizes: 0.70–1.38), as were HR (166 ± 20 vs 104 ± 15 beats·min⁻¹, p < 0.05) and ventilation (59.2 ± 28.8 vs 35.1 ± 16.6 L·min⁻¹, p = 0.01).ConclusionsRPE_P was dominant over RPE_C during wheelchair propulsion for untrained AB participants. For athletes with CSCI, lower RPE_P and RPE_C were reported at the same %V̇O_2peak compared to those without CSCI. The mechanism for this remains to be fully elucidated.