Relationship between interchange usage and risk of hamstring injuries in the Australian Football League

Injury in Starting and Replacement Players from Five Professional Men's Rugby Unions

OBJECTIVES

The aim of this study was to compare the incidence, severity, and burden of injury in starting and replacement players from professional men's teams of five rugby unions.

METHODS

Match injuries of greater than 24 h time-loss (including data on the severity, match quarter, event, body region) and player minutes of match exposure data were collated for all starting and replacement players in the men's English Premiership, Welsh Pro14 (both 2016/17-2018/19 seasons), and Australian, New Zealand, and South African Super Rugby (all 2016-2018 seasons) teams. Injury incidences and mean injury burden (incidence × days missed) were calculated, and rate ratios (RRs) (95% confidence intervals [CIs]) were used to compare injury incidence and burden between starting (reference group) and replacement players.

RESULTS

Overall injury incidence was not different between starters and replacements for all injuries (RR = 0.98, 95% CI 0.88-1.10), nor for concussions (RR = 0.85; 95% CI 0.66-1.11). Mean injury burden was higher for replacement players (RR = 1.31, 95% CI 1.17-1.46). Replacement injury incidence was lower than the starters in the third (RR = 0.68, 95% CI 0.51-0.92) and fourth (RR = 0.78, 95% CI 0.67-0.92) match quarters. Injury incidence was not different between starters and replacements for any match event or body region, but compared with starters, replacements' injury burden was higher in lower limbs (RR = 1.24, 95% CI 1.05-1.46) and in the tackled player (RR = 1.30, 95% CI 1.01-1.66).

CONCLUSION

This study demonstrated a lower injury incidence in replacement players compared with starters in the second half of matches, with a higher injury burden for replacement players due to higher mean injury severity.

Lower extremity isokinetic strength characteristics of amateur boxers

Aim: Sufficient strength and dynamic stability of the lower limbs are essential for improving punching force and preventing injury in amateur boxers. However, there are still no comprehensive reports on the isokinetic knee strength of boxers with different performance levels. The current study aimed to profile the isokinetic muscle strength of flexion and extension of the knee in boxers, as well as bilateral, unilateral, and functional ratios, and investigate the variation in these muscle strength characteristics associated with different performance levels.

Methods: Boxers were divided in two performance groups, elite (five males and four females) and non-elite groups (five males and four females). Muscle strength of the knee was determined via an IsoMed2000 device. Parameters examined included peak torque of the hamstring (H) and quadriceps (Q) during concentric (con) and eccentric (ecc) contractions at low (60°/S), medium (180°/S), and high (240°/S) speed and bilateral ratios (BLs), unilateral ratios (ULs), and functional ratios of dominant (D) and non-dominant limbs.

Results: In all angular velocities, the peak torque of H and Q was stronger in the elite group than in the non-elite group. ULs were lower in the elite group than in the non-elite group in Hcon/Qcon at 180D (p < 0.01) and 180ND (p < 0.05) and in Hecc/Qecc at 60D, 180D (p < 0.05) and 240D (p < 0.01). The elite group had higher BLs than the non-elite group in Hcon at 60°/S (p < 0.05) and Qcon at 180°/S (p < 0.05). The non-elite group had a higher functional ratio than elite boxers in Hecc/Qcon at 180D and 240D (p < 0.01).

Conclusion: Elite boxers had stronger knee strength in con and ecc contractions. All boxers had normal Hecc/Qecc and Hcon/Qecc. Hcon/Qcon and Hecc/Qcon were abnormal at lower angular velocity. Elite boxers had higher BLs and lower ULs, indicating that they are at a higher risk of injury.

Injuries During Return to Sport After the COVID-19 Lockdown: An Epidemiologic Study of Italian Professional Soccer Players

Background:

The injury rate in professional soccer players may be influenced by match frequency.

Purpose:

To assess how changes in match frequency that occurred because of coronavirus disease 2019 (COVID-19) influenced training and match injuries in the Italian Serie A league.

Study Design:

Descriptive epidemiology study.

Methods:

Three phases in the Serie A league, each 41 days long, were evaluated: phase A was the beginning of the 2019-2020 season; phase B was a period after the COVID-19 lockdown was lifted, when the remaining matches of the season were played with greater frequency; and phase C was the beginning of the 2020-2021 season. All male professional soccer players who were injured during the 3 phases were included. Player age, height, position, injury history, and return to play (RTP) were retrieved from a publicly available website. Training- and match-related injuries during each of the 3 phases were collected and compared. Moreover, match injuries that occurred after the lockdown phase (phase B), in which there were 12 days designated for playing matches (“match-days”), were compared with injuries in the first 12 match-days of phases A and C.

Results:

When comparing 41-day periods, we observed the injury burden (per 1000 exposure-hours) was significantly lower in phase B (278.99 days absent) than in phase A (425.4 days absent; P < .05) and phase C (484.76 days absent; P < .05). A longer mean RTP period was recorded in phase A than in phase B (44.6 vs 23.1 days; P < .05). Regarding 12–match day periods (81 days in phase A, 41 days in phase B, and 89 days in phase C), there was a significantly higher match injury rate (0.56 vs 0.39 injuries/1000 exposure-hours; P < .05) and incidence (11.8% vs 9.3%; P < .05) in phase B than in phase A and a longer mean RTP period in phase A than in phase B (41.8 vs 23.1 days; P < .05). Finally, the rate and incidence of training-related injuries were significantly higher in phase B (4.6 injuries/1000 exposure-hours and 6.5, respectively) than in phase A (1.41 injuries/1000 exposure-hours and 2.04, respectively) (P < .05).

Conclusion:

Both training- and match-related injuries were greater during the abbreviated period after the COVID-19 lockdown. These may be linked to the greater match frequency of that period.

The influence of fixture congestion on physical performance response to U23 soccer match-play

This study sought to examine differences in measures of intense periods of physical performance during competitive match-play, between one-match (1 match weeks) and two-match microcycles (2 match week). 1, 3 and 5 min "peak" and mean averages for total distance (TD), high-speed running (HSR) and metabolic power (MP) were analysed for each 15 min period of match-play. Linear mixed models were employed to examine the differences in dependent variables for each method of measurement between the 1 and 2 game microcycles. No differences were reported for "peak" values for all epoch lengths, however, results revealed significantly reduced "average" values, during periods of fixture congestion, for 1, 3 and 5 min epochs for average TD, and 3 min epochs for average HSR towards the end of the match (75-90 min split). There was, however, a trend for the opposite response to occur in the 60-75-min period. The current data suggests that players potentially display altered pacing strategies during periods of fixture congestion, with these observed responses being dependent on sampling method and epoch length.

Evolution of Physical Demands of Australian Football League Matches from 2005 to 2017: A Systematic Review and Meta-Regression

BACKGROUND

There is extensive research investigating the match demands of players in the Australian Football League (AFL).

OBJECTIVE

This systematic literature review and meta-regression sought to analyse the evolution of in-game demands in AFL matches from 2005 to 2017, focusing on the relationship between volume and intensity.

METHODS

A systematic search of Ovid MEDLINE, Embase, Emcare, Scopus, SPORTDiscus, and Cochrane Library databases was conducted. Included studies examined the physical demands of AFL matches utilising global positioning system (GPS) technology. Meta-regression analysed the shift in reported volume (total distance and total match time) and intensity (metres per minute [m.min^-1], sprint duration and acceleration) metrics for overall changes, across quarters and positional groups (forwards, nomadics and defenders) from 2005 to 2017 inclusive and for each year between 2005 and 2007, 2007 and 2010, 2010 and 2012, and 2012 and 2015/2017 breakpoints.

RESULTS

Distance (p = 0.094), m.min^-1 (p = 0.494), match time (p = 0.591), time over 18 km·h^-1 (p = 0.271), and number of accelerations greater than 4 km·h^-1 (p = 0.498) and 10 km·h^-1 (p = 0.335) in 1 s did not change from 2005 to 2017. From 2005 to 2007 volume decreased (- 6.10 min of match time; p = 0.010) and intensity increased (6.8 m.min^-1 increase; p = 0.023). Volume and intensity increased from 2007 to 2010, evidenced by increases in total distance (302 m; p = 0.039), time over 18 km·h^-1 (0.31 min; p = 0.005), and number of accelerations greater than 4 km·h^-1 (41.1; p = 0.004) and 10 km·h^-1 (3.6; p = 0.005) in 1 s. From 2010 to 2012, intensity decreased, evidenced by reductions in metres per minute (- 4.3; p = 0.022), time over 18 km·h^-1 (- 0.93 min; p < 0.001), and number of accelerations greater than 4 km·h^-1 (- 104.4; p < 0.001) and 10 km·h^-1 (- 8.3; p < 0.001) in 1 s, whilst volume stabilised with no changes in distance (p = 0.068) and match time (p = 0.443). From 2012 to 2015/2017 volume remained stable and intensity increased with time over 18 km·h^-1 (0.27 min; p = 0.008) and number of accelerations greater than 4 km·h^-1 (31.6; p = 0.016) in 1 s increasing.

CONCLUSIONS

Changes in volume and intensity of AFL match demands are defined by discrete periods from 2007 to 2010 and 2010 to 2012. The interaction of rule and interpretation changes and coaching strategies play a major role in these evolutionary changes. In turn, modified game styles impact player game demands, training, and selection priorities. Standardisation and uniformity of GPS data reporting is recommended due to inconsistencies in the literature.

A League-Wide Evaluation of Factors Influencing Match Activity Profile in Elite Australian Football

Introduction: Accurate interpretation of activity profile data requires an understanding of the variables influencing player movement during matches.

Methods: Over 65,000 stints (player rotations) from all 207 matches of the 2018 Australian Football League (AFL) season were evaluated. The relative activity profile including total distance per minute (TD), high-speed running distance per minute (HSR) and Player Load^TM per minute (PL) was determined for each stint and analysed against a range of match-related, player-related and environment-related predictor variables using multivariate linear mixed modelling. Effect size statistics along with the uncertainty in the estimates (95% confidence interval) were used to interpret the findings.

Results: The smallest important effects on TD, HSR, and PL were calculated as 1.5%, 5.5%, and 2.4%, respectively. Stint duration had small to moderate negative effects on TD (−6%), PL (−7.7%), and HSR (−13%), while recovery duration between stints had a small positive effect on HSR (+7%). There were moderate reductions in TD (−8%), HSR (−23%), and PL (−9.6%) in the last quarter compared to the first quarter of matches, while similar reductions existed in subsequent stints compared to the first stint in each quarter. Moderate to large differences of up to 9% in TD, 48% in HSR and 12% in PL existed between positions. The TD of less experienced players was slightly higher than their more experienced counterparts (2–3%). A 5% increase in body mass was associated with a small reduction in HSR (−5.5%). There were small reductions in TD (−2%), HSR (−10%), and PL (−3%) during the Finals Series compared to the Premiership Season. Moderate levels of rainfall during matches and higher apparent temperatures had small negative effects on TD (−2%) and HSR (−6 and −9%). The number of days break between matches, score margin, match outcome, ground hardness, ground size, and traveling for the current or the previous match had trivial effects on the activity profile.

Conclusion: Player position and stage of the match (quarter) had the largest effects on match activity profile while stint duration, recovery duration, stint timing, professional experience, body mass, stage of the season, and weather conditions also had substantial effects.

Fifteen-week window for recurrent muscle strains in football: a prospective cohort of 3600 muscle strains over 23 years in professional Australian rules football

OBJECTIVES

To determine the rates of muscle strain injury recurrence over time after return to play in Australian football and to quantify risk factors.

METHODS

We analysed Australian Football League player data from 1992 to 2014 for rates of the four major muscle strain injury types (hamstring, quadriceps, calf and groin) diagnosed by team health professionals. Covariates for analysis were: recent history (≤8 weeks) of each of the four muscle strains; non-recent history (>8 weeks) of each; history of hip, knee anterior cruciate ligament, knee cartilage, ankle sprain, concussion or lumbar injury; age; indigenous race; match level and whether a substitute rule was in place.

RESULTS

3647 (1932 hamstring, 418 quadriceps, 458 calf and 839 groin) muscle strain injuries occurred in 272 759 player matches. For all muscle strains combined, the risk of injury recurrence gradually reduced, with recurrence risks of 9% (hamstring), 5% (quadriceps), 2% (calf) and 6% (groin) in the first match back and remaining elevated for 15 weeks after return to play. The strongest risk factor for each muscle injury type was a recent history of the same injury (hamstring: adjusted OR 13.1, 95% CI 11.5 to 14.9; calf OR 13.3, 95% CI 9.6 to 18.4; quadriceps: OR 25.2, 95% CI 18.8 to 33.8; groin OR 20.6, 95% CI 17.0 to 25.0), followed by non-recent history of the same injury (hamstring: adjusted OR 3.5, 95% CI 3.2 to 3.9; calf OR 4.4, 95% CI 3.6 to 5.4; quadriceps OR 5.2, 95% CI 4.2 to 6.4; groin OR 3.5, 95% CI 3.0 to 4.0). Age was an independent risk factor for calf muscle strains (adjusted OR 1.6, 95% CI 1.3 to 2.0). Recent hamstring injury increased the risk of subsequent quadriceps (adjusted OR 1.8, 95% CI 1.2 to 2.7) and calf strains (OR 1.8, 95% CI 1.2 to 2.6). During the 'substitute rule' era (2011-2014), hamstring (adjusted OR 0.76, 95% CI 0.67 to 0.86), groin (OR 0.78, 95% CI 0.65 to 0.93) and quadriceps (OR 0.70, 95% CI 0.53 to 0.92) strains were less likely than outside of that era but calf (OR 1.6, 95% CI 1.3 to 1.9) strains were more likely than before the substitute rule era.

CONCLUSION

Recent injury is the greatest risk factor for the four major muscle strains, with increased risk persisting for 15 weeks after return to play.

Recalibrating the risk of hamstring strain injury (HSI): A 2020 systematic review and meta-analysis of risk factors for index and recurrent hamstring strain injury in sport

OBJECTIVE

To systematically review risk factors for hamstring strain injury (HSI).

DESIGN

Systematic review update.

DATA SOURCES

Database searches: (1) inception to 2011 (original), and (2) 2011 to December 2018 (update). Citation tracking, manual reference and ahead of press searches.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Studies presenting prospective data evaluating factors associated with the risk of index and/or recurrent HSI.

METHOD

Search result screening and risk of bias assessment. A best evidence synthesis for each factor and meta-analysis, where possible, to determine the association with risk of HSI.

RESULTS

The 78 studies captured 8,319 total HSIs, including 967 recurrences, in 71,324 athletes. Older age (standardised mean difference=1.6, p=0.002), any history of HSI (risk ratio (RR)=2.7, p<0.001), a recent HSI (RR=4.8, p<0.001), previous anterior cruciate ligament (ACL) injury (RR=1.7, p=0.002) and previous calf strain injury (RR=1.5, p<0.001) were significant risk factors for HSI. From the best evidence synthesis, factors relating to sports performance and match play, running and hamstring strength were most consistently associated with HSI risk. The risk of recurrent HSI is best evaluated using clinical data and not the MRI characteristics of the index injury.

SUMMARY/CONCLUSION

Older age and a history of HSI are the strongest risk factors for HSI. Future research may be directed towards exploring the interaction of risk factors and how these relationships fluctuate over time given the occurrence of index and recurrent HSI in sport is multifactorial.

Exploring the association between recent concussion, subconcussive impacts and depressive symptoms in male Australian Football players

Objectives

To explore the association between depressive symptoms and recent head-related trauma (diagnosed concussion, subconcussive impacts) in semiprofessional male Australian Football (AF) players.

Methods

Sixty-nine semiprofessional male players from a West Australian Football League (WAFL) club participated in the study (M_age=21.81, SD=2.91 years). Depressive symptoms were measured using the Centre for Epidemiological Studies Depression Scale. Injuries and potential confounding variables (eg, pre-existing mental health condition; alcohol or drug hangovers; experiencing a stressful event) were self-reported anonymously using the WAFL Injury Report Survey. Both tools were administered every 2-weeks over the first 22-weeks of the WAFL season. Controlling for potential confounding variables and other injuries, a repeated measures generalised estimating equations model assessed the risk of clinically relevant depressive symptoms occurring, when diagnosed concussion or subconcussive impacts were experienced.

Results

A total of 10 concussions and 183 subconcussive impacts were reported. Players who experienced a concussion were almost nine times more likely to experience clinically relevant depressive symptoms (OR 8.88, 95% CI 2.65 to 29.77, p<0.001). Although elevated, depressive symptoms following subconcussive impacts were not statistically significant (OR 1.13, 95% CI 0.67 to 1.92, p=0.641).

Conclusion

These findings indicate that semiprofessional AF athletes may be at risk of experiencing depressive symptoms after concussion. Severity (concussion vs subconcussive impacts) and dose (number of impacts) appear to have an important relationship with depressive symptom outcomes in this cohort and should be considered for further research and management of player welfare.

Relationships between Body Build and Knee Joint Flexor and Extensor Torque of Polish First-Division Soccer Players

The aim of the study is to identify the relationships between anthropometric variables and knee joint extensor peak torque, knee joint flexor peak torque, and conventional hamstring-to-quadriceps ratio in Polish first-division soccer players. The study examined 37 soccer players aged 19 to 30 years (body mass: 76.8 ± 7.2 kg, body height 1.82 ± 0.06 m). Muscle torques of the knee joint were measured under isometric conditions using a Biodex 4 Pro dynamometer. The anthropometric variables such as body part lengths, breadths, and girths and skinfold thickness were measured. The strongest relationships of knee joint extensors were observed with body mass and variables describing skeleton size and lower-limb muscles. Regarding knee flexor torque, a significant relationship was found only with body mass. However, no significant relationships were observed between the conventional hamstring-to-quadriceps ratio and the anthropometric variables studied. The regression analysis results identified body height, body mass, and thigh and calf girth as the features most associated with knee joint torque. However, anthropometric measurements do not provide full information about the torque proportions of antagonist muscle groups, which is very important for injury prevention. Therefore, measurements using special biomechanical equipment are also necessary for the comprehensive analyses and control of the effects of sports training.

Australian Football League Injury Characteristics Differ Between Matches and Training: A Longitudinal Analysis of Changes in the Setting, Site, and Time Span From 1997 to 2016

Background:

Injury surveillance has been used to quantify the scope of the injury burden in Australian football. However, deeper statistical analyses are required to identify major factors that contribute to the injury risk and to understand how these injury patterns change over time.

Purpose:

To compare Australian Football League (AFL) injury incidence, severity, prevalence, and recurrence by setting, site, and time span from 1997 to 2016.

Study Design:

Descriptive epidemiology study.

Methods:

A total of 15,911 injuries and medical illnesses recorded by team medical staff at each club were obtained from the AFL’s injury surveillance system and analyzed using linear mixed models with 3 fixed effects (setting, time span, site) and 1 random effect (club). All types of injuries and medical illnesses were included for analysis, provided that they caused the player to miss at least 1 match during the regular season or finals. Five-season time spans (1997-2001, 2002-2006, 2007-2011, and 2012-2016) were used for comparisons. Incidence rates were expressed at the player level. Recurrences were recoded to quantify recurrent injuries across multiple seasons.

Results:

Compared with training injuries, match injuries had a 2.8 times higher incidence per season per club per player (matches: 0.070 ± 0.093; training: 0.025 ± 0.043; P < .001). Match injuries resulted in 1.9 times more missed matches per club per season (matches: 17.2 ± 17.0; training: 9.1 ± 10.5; P < .001). and were more likely to be recurrences (matches: 11.6% ± 20.0%; training: 8.6% ± 21.8%; P < .001). From the 1997-2001 to 2007-2011 time spans, overall injury severity increased from a mean of 3.2 to 3.7 missed matches (P ≤ .01). For the most recent 2012-2016 time span, injuries resulted in 3.6 missed matches, on average. Hip/groin/thigh injuries had the highest incidence (0.125 ± 0.120) and prevalence (19.2 ± 16.4) rates, and recurrences (29.3% ± 27.9%) were 15% more likely at this site than any other injury site.

Conclusion:

The risks of match injuries are significantly higher than those of training injuries in the AFL. Compared with the 1997-2001 time span, injuries became more severe during the 2007-2011 time span.

Isokinetic strength assessment offers limited predictive validity for detecting risk of future hamstring strain in sport: a systematic review and meta-analysis

Objective

To examine the value of isokinetic strength assessment for predicting risk of hamstring strain injury, and to direct future research into hamstring strain injuries.

Design

Systematic review.

Data sources

Database searches for Medline, CINAHL, Embase, AMED, AUSPORT, SPORTDiscus, PEDro and Cochrane Library from inception to April 2017. Manual reference checks, ahead-of-press and citation tracking.

Eligibility criteria for selecting studies

Prospective studies evaluating isokinetic hamstrings, quadriceps and hip extensor strength testing as a risk factor for occurrence of hamstring muscle strain.

Methods

Independent search result screening. Risk of bias assessment by independent reviewers using Quality in Prognosis Studies tool. Best evidence synthesis and meta-analyses of standardised mean difference (SMD).

Results

Twelve studies were included, capturing 508 hamstring strain injuries in 2912 athletes. Isokinetic knee flexor, knee extensor and hip extensor outputs were examined at angular velocities ranging 30–300°/s, concentric or eccentric, and relative (Nm/kg) or absolute (Nm) measures. Strength ratios ranged between 30°/s and 300°/s. Meta-analyses revealed a small, significant predictive effect for absolute (SMD=−0.16, P=0.04, 95% CI −0.31 to −0.01) and relative (SMD=−0.17, P=0.03, 95% CI −0.33 to −0.014) eccentric knee flexor strength (60°/s). No other testing speed or strength ratio showed statistical association. Best evidence synthesis found over half of all variables had moderate or strong evidence for no association with future hamstring injury.

Summary/Conclusion

Despite an isolated finding for eccentric knee flexor strength at slow speeds, the role and application of isokinetic assessment for predicting hamstring strain risk should be reconsidered, particularly given costs and specialised training required.

Angle-Specific Eccentric Hamstring Fatigue After Simulated Soccer

Purpose:

To evaluate the effect of simulated soccer on the hamstrings eccentric torque-angle profile and angle of peak torque (APTeccH), and on the hamstrings:quadriceps torque ratio at specific joint angles (ASHecc:Qcon).

Methods:

The authors assessed dominant-limb isokinetic concentric and eccentric knee flexion and concentric knee extension at 120°/s in 9 semiprofessional male soccer players immediately before and after they completed the Loughborough Intermittent Shuttle Test (LIST).

Results:

The LIST resulted in significant decreases in eccentric hamstrings torque at 60°, 50°, and 10° and a significant (21.8%) decrease in ASHecc:Qcon at 10° (P < .05). APTeccH increased from 7.1° ± 1.0° to 18.8° ± 4.2° (P < .05). Eccentric hamstrings peak torque significantly declined from 185.1 ± 70.4 N·m pre-LIST to 150.9 ± 58.5 N·m post-LIST (P = .002), but there were no significant changes in hamstrings or quadriceps concentric peak torque (P = .312, .169, respectively).

Conclusions:

Simulated soccer results in a selective loss of eccentric hamstrings torque and hamstrings-to-quadriceps muscle balance at an extended joint position and a shift in the eccentric hamstrings APT to a shorter length, changes that could increase vulnerability to hamstrings injury. These findings suggest that injury-risk screening could be improved by evaluating the eccentric hamstrings torque-angle profile and hamstrings strength-endurance and that the development of hamstrings fatigue resistance and long-length eccentric strength may reduce injury incidence.

Cricket fast bowling workload patterns as risk factors for tendon, muscle, bone and joint injuries

OBJECTIVE

To assess workload-related risk factors for injuries to particular tissue types in cricket fast bowlers.

DESIGN

235 fast bowlers who bowled in 14600 player innings over a period of 15 years were followed in a prospective cohort risk factor study to compare overs bowled in each match (including preceding workload patterns) and injury risk in the 3-4 weeks subsequent to the match. Injuries were categorised according to the affected tissue type as either: bone stress, tendon injuries, muscle strain or joint injuries. Workload risk factors were examined using binomial logistic regression multivariate analysis, with a forward stepwise procedure requiring a significance of <0.05.

RESULTS

High acute match workload and high previous season workload were risk factors for tendon injuries, but high medium term (3-month workload) was protective. For bone stress injuries, high medium term workload and low career workload were risk factors. For joint injuries, high previous season and career workload were risk factors. There was little relationship between muscle injury and workload although high previous season workload was slightly protective.

CONCLUSIONS

The level of injury risk for some tissue types varies in response to preceding fast bowling workload, with tendon injuries most affected by workload patterns. Workload planning may need to be individualised, depending on individual susceptibility to various injury types. This study supports the theory that tendons are at lowest risk with consistent workloads and susceptible to injury with sudden upgrades in workload. Gradual upgrades are recommended, particularly at the start of a bowler's career to reduce the risk of bone stress injury.

Analysis of the Three Most Prevalent Injuries in Australian Football Demonstrates a Season to Season Association Between Groin/Hip/Osteitis Pubis Injuries With ACL Knee Injuries

Background:

Injuries are common in contact sports like Australian football. The Australian Football League (AFL) has developed an extensive injury surveillance database that can be used for epidemiological studies.

Objectives:

The purpose of this study is to identify any association between the three most prevalent injuries in the AFL.

Patients and Methods:

From the AFL injury surveillance data 1997-2012 the injury incidence (new injuries per club per season) and the injury prevalence data (missed games per club per season) were analysed to detect the three most common injuries that would cause a player to miss a match in the AFL. The three most prevalent injuries in the AFL are hamstring strains, groin/hip/osteitis pubis injuries and Anterior Cruciate Ligament (ACL) knee injuries. Following this, further study was undertaken to detect the presence of any statistical relationship between injury incidences of the three most prevalent injuries over this sixteen year study period.

Results:

Statistical analysis demonstrates for any given year that there was an association between having a groin/hip/osteitis pubis injuriy and having a knee ACL injury (P < 0.05) over the entire sixteen years. In other words if the number of groin/hip/osteitis pubis injuries in any given season were higher than average (alternatively lower) then the number of knee ACL injuries were also higher than average (alternatively lower) for that same season. Hamstring injuries had the highest variance of incidence of the three most prevalent injuries.

Conclusions:

Analysis of the AFL injury data demonstrates an association between incidence of groin/hip/osteitis pubis injuries and incidence of knee ACL injuries for any given playing season. This finding is difficult to explain with further research being required.

Time trends for injuries and illness, and their relation to performance in the National Basketball Association

OBJECTIVES

To survey injury/illness in the National Basketball Association over a 25-year period and examine the relationship of injury/illness to team performance.

DESIGN

A retrospective correlational design.

METHODS

Trends were examined in reported numbers of players injured/ill during a season and games missed due to injury/illness from seasons ending in 1986 through 2005. This period was compared to years 2006-2010, when NBA teams were allowed to increase the total number of players on the team from 12 to 15.

RESULTS

There was a highly significant trend (p<0.0001) of increasing numbers of players injured/ill and games missed from 1986 through 2005. After the team expansion in 2006, these rates fell abruptly by 13% and 39% respectively (both p<0.0001 compared to the previous 5-year period). We also found a significant inverse association between games missed due to injury/illness and percent games won (r=-0.29, p<0.0001).

CONCLUSIONS

Results demonstrate an increased rate of injury in the National Basketball Association up until the expansion of team size in 2006. Following 2006, team expansion was positively associated with decreased injury/illness rates. The latter finding suggests the importance of maintaining a healthy roster with respect to winning outcomes.

Results of 2 decades of injury surveillance and public release of data in the Australian Football League

BACKGROUND

Injuries are common in all professional football codes (including soccer, rugby league and union, American football, Gaelic football, and Australian football).

PURPOSE

To report the epidemiology of injuries in the Australian Football League (AFL) from 1992-2012 and to identify changes in injury patterns during that period.

STUDY DESIGN

Descriptive epidemiology study.

METHODS

The AFL commenced surveying injuries in 1992, with all teams and players included since 1996. An injury was defined as "any physical or medical condition that causes a player to miss a match in the regular season or finals (playoffs)." Administrative records of injury payments (which are compulsory as part of salary cap compliance) to players who do not play matches determined the occurrence of an injury. The seasonal incidence was measured in units of new injuries per club (of 40 players) per season (of 22 matches).

RESULTS

There were 4492 players listed over the 21-year period who suffered 13,606 new injuries/illnesses and 1965 recurrent injuries/illnesses, which caused 51,919 matches to be missed. The lowest seasonal incidence was 30.3 new injuries per club per season recorded in 1993, and the highest was 40.3 recorded in 1998. The injury prevalence (missed matches through injury per club per season) varied from a low of 116.3 in 1994 to a high of 157.1 in 2011. The recurrence rate of injuries was highest at 25% in 1992 and lowest at 9% in 2012 and has steadily fallen across the 21 years (P < .01). The most frequent and prevalent injury was hamstring strain (average of 6 injuries per club per season, resulting in 20 missed matches per club per season; recurrence rate, 26%), although the rate of hamstring injuries has fallen in the past 2 seasons after a change to the structure of the interchange bench (P < .05). The rate of knee posterior cruciate ligament injuries fell in the years after a rule change to prevent knee-to-knee collisions in ruckmen (P < .01).

CONCLUSION

Annual public reporting (by way of media release and reports available freely online) of injury rates, using units easily understood by laypeople, has been well received. It has also paved the way for rule changes with the primary goal of improving player safety.

The effects of game and training loads on perceptual responses of muscle soreness in Australian football

Australian Football is an intense team sport played over ~120 min on a weekly basis. To determine the effects of game and training load on muscle soreness and the time frame of soreness dissipation, 64 elite Australian Football players (age 23.8 ± 1.8 y, height 183.9 ± 3.8 cm, weight 83.2 ± 5.0 kg; mean ± SD) recorded perceptions of muscle soreness, game intensity, and training intensity on scales of 1-10 on most mornings for up to 3 competition seasons. Playing and training times were also recorded in minutes. Data were analyzed with a mixed linear model, and magnitudes of effects on soreness were evaluated by standardization. All effects had acceptably low uncertainty. Game and training-session loads were 790 ± 182 and 229 ± 98 intensity-minutes (mean ± SD), respectively. General muscle soreness was 4.6 ± 1.1 units on d 1 postgame and fell to 1.9 ± 1.0 by d 6. There was a small increase in general muscle soreness (0.22 ± 0.07-0.50 ± 0.13 units) in the 3 d after high-load games relative to low-load games. Other soreness responses showed similar timelines and magnitudes of change. Training sessions made only small contributions to soreness over the 3 d after each session. Practitioners should be aware of these responses when planning weekly training and recovery programs, as it appears that game-related soreness dissipates after 3 d regardless of game load and increased training loads in the following week produce only small increases in soreness.