Relationship between leg stiffness and lower body injuries in professional Australian football

Abstract

Leg stiffness is a modifiable mechanical property that may be related to soft tissue injury risk. The purpose of this study was to examine mean leg stiffness and bilateral differences in leg stiffness across an entire professional Australian Football League (AFL) season, and determine whether this parameter was related to the incidence of lower body soft tissue injury. The stiffness of the left and right legs of 39 professional AFL players (age 24.4 ± 4.4 years, body mass 87.4 ± 8.1 kg, stature 1.87 ± 0.07 m) was measured using a unilateral hopping test at least once per month throughout the season. Injury data were obtained directly from the head medical officer at the football club. Mean leg stiffness and bilateral differences in leg stiffness were compared between the injured and non-injured players. There was no difference between the season mean leg stiffness values for the injured (219.3 ± 16.1 N · m^?1 · kg^?1) and non-injured (217.4 ± 14.9 N · m^?1 · kg^?1; P = 0.721) groups. The injured group (7.5 ± 3.0%) recorded a significantly higher season mean bilateral difference in leg stiffness than the non-injured group (5.5 ± 1.3%; P = 0.05). A relatively high bilateral difference in leg stiffness appears to be related to the incidence of soft tissue injury in Australian football players. This information is of particular importance to medical and conditioning staff across a variety of sports.     

Relationship between vertical stiffness and soft-tissue injuries in professional Australian football

ABSTRACT

Soft-tissue injuries are common in Australian football. Recently, literature has identified non-modifiable and modifiable risk factors, including vertical stiffness (K_vert). However, limitations regarding measurement frequency and duration exist; thus, further information is required about the role of K_vert as a modifiable risk factor for injury. This study examined the seasonal variation in K_vert and its relationship to soft-tissue injuries in professional Australian football. The mean K_vert and bilateral asymmetry were assessed and compared between injured and non-injured players. For the seasonal analysis, 56 players were tested across two seasons with no variation in bilateral asymmetry evident (p= 0.33). While there were generally no changes in K_vert, the value from the end of the second pre-season revealed 5% lower values than the mean of two seasons (p= 0.02). Considering the injury analysis, 21 lower-body soft-tissue injuries were recorded from 18 participants. No differences were recorded for mean K_vert between the injured and non-injured groups (p= 0.16–0.76). When assessing K_vert asymmetry, the injured group displayed a 4.5% higher value than the non-injured group at the end of the pre-season test (p= 0.03) but not at other time-points (p= 0.16–0.99). Higher K_vert bilateral asymmetry measures after the pre-season appear to be related to lower-body soft-tissue injury in professional Australian footballers. Medical and conditioning staff should consider this measure when trying to mitigate the onset of injury or identify at-risk players.     

The relationship between lower body stiffness and injury incidence in female netballers

The aim of this study was to provide contemporary information on injury rates in an elite and sub-elite netball population and to explore the relationship between lower body stiffness and lower body injuries. One elite and two sub-elite teams of female netballers (n = 29) performed the vertical hop test to assess active lower body stiffness (K_vert) and myometry to assess quasi-static stiffness. Lower body injuries were monitored via self-reporting and liaison with physiotherapists. Twelve lower body non-contact injuries were sustained by 10 players, equating to 11.29 lower body injuries per 1,000 exposure hours. The most commonly injured sites were the calf (33%) and ankle (25%). No significant differences between K_vert of injured and non-injured players were reported, however, injured elite players recorded significantly higher season mean quasi-static stiffness in the soleus (p = 0.037) and Achilles (p = 0.004) than non-injured elite players. Elite and sub-elite netball players recorded a higher injury incidence than previous reports of injuries in recreational netballers. Within the constraints of the study, relatively high stiffness of the soleus and Achilles appears to be related to lower body non-contact injury incidence in female netballers, particularly at the elite level. These results provide a basis for development of injury prevention strategies.     

我国儿童足球训练运动损伤初探:基于992名6~9岁球员的横断面研究

目的：调查我国6~9岁儿童在足球训练中运动损伤的患病率、患病特点、影响因素。方法：本横断面研究纳入2017—2019年中国足球小将相关赛事报名参赛球员,收集人口基本信息、足球训练情况、足球训练相关损伤情况。结果：研究纳入992例球员,来自全国16个省和直辖市。其中男性儿童953人、女性儿童39人,平均年龄(8.1±0.8)岁,平均身高(135.3±6.8) cm,平均体重(29.0±4.7) kg,平均BMI(15.8±1.8) kg/m2,平均球龄(28.7±10.5)月。足球训练中运动损伤的患病率为15.0%。损伤最常见的部位为踝关节;最常见受伤类型是关节扭伤或韧带损伤。受伤球员与未受伤球员间最大训练强度有统计学差异(P<0.05),性别、年龄、场上位置、每次训练时间、每周训练频率无统计学差异。结论：我国6~9岁参与足球运动的儿童在训练中出现运动损伤的患病率为15%。其中踝关节扭伤最常见。训练强度过高很可能是导致发生训练损伤的风险因素。     

Science and Gaelic football: a review

This review focuses on Gaelic football and scientific reports of the characteristics of its players and the demands of the game. Anthropometric characteristics vary according to positional role, but top players display high muscularity and good all-round fitness at the peak of the competitive season. Match analysis indicates that exercise intensity is roughly equivalent to that for professional soccer. Average heart rates are approximately 160 beats x min(-1) during competitive matches, and average oxygen consumption is about 72% of maximum. Metabolic fatigue in active muscles is unlikely. Conventional biomechanical and electromyographic techniques are useful in gaining insight into individual games skills. Inadequate attention has been given to injury prevention and to psychological aspects of the game. Although possessing unique characteristics, Gaelic football has many similarities with other football codes, especially Australian Rules football where the ball is played by both hands and feet and where tackling is permitted.     

Relative age effects in Australian Football League National Draftees

Abstract

This study examined the birth distribution for adolescent (i.e. <20 years) and mature age players (i.e. ≥20 years) selected in the Australian Football League (AFL) National Draft between 2001 and 2012. Birth-date information was accessed for all first time AFL national draftees and players were then classified as either adolescent (N = 736) or mature age (N = 70) draftees. Chi-squared analysis showed a clear bias in the birth distribution of adolescent draftees towards players born in the first part of the classification period for both quartile (P < 0.001) and half-year (P < 0.001) compared to the Australian national population. There was a reverse relative age effect (RAE) for mature age draftees, with a significant bias towards players born in the latter part of the selection period for both quartile (P = 0.047) and half-year (P = 0.028) compared to the Australian national population. The selection bias towards relatively older players in adolescent AFL draftees may be related to advanced physical and psychological maturity, and exposure to higher-level coaching compared to their younger counterparts. The reverse RAE in mature age draftees is a novel finding and supports the need for strategies to encourage continued participation pathways for talented Australian football players born later in the selection year.     

Groin injuries in professional rugby league players: a prospective study

Altogether, 100 uninjured professional rugby league players were evaluated over a 2-year period. Their height, body mass, sum of skinfolds, girths and bone diameters were recorded. A Cybex 340 isokinetic dynamometer was used to determine peak torque, work, power, endurance ratios and peak torque ratios of the hip abductors and adductors (5 repetitions at 0.52 and 2.08 rad. s(- 1); 20 repetitions at 3.66 rad. s(- 1)) and knee flexors and extensors (4 repetitions at 1.04 and 3.14 rad. s(- 1); 30 repetitions at 5.22 rad. s(- 1)). Hip abduction and adduction were also assessed with the hip in external rotation. Discriminant function analysis was conducted on all predictor variables to develop a multivariate predictive model capable of classifying players with a high degree of accuracy into groups with and without a groin injury. The model consisted of eight variables and correctly classified 91.7% of the non-injured players and 90.5% of the injured players. The correct classification for the model as a whole was 91.4%. The aetiological factors identified as being related to injury of the groin musculotendinous unit included abduction and adduction-with-rotation peak torque, angle of adduction and abduction-with-rotation peak torque, strength ratio of hip muscle groups, bilateral difference in extension peak torque, femur diameter and body mass.     

Comparison of athletic movement between elite junior and senior Australian football players

This study compared the athletic movement skill between elite Under-18 (U18) Australian football (AF) and senior Australian Football League (AFL) players. The U18 sample (n = 13; 17.7 ± 0.6 years) were representatives of an elite talent development programme. The AFL players were classified accordingly; Group 1 (1–4 AFL seasons; n = 20; 21.2 ± 1.9 years) and Group 2 (>5 AFL seasons; n = 14; 26.3 ± 2.6 years). Participants performed an athletic movement skill assessment, inclusive of five foundational movements. Each movement was scored across three assessment points using a three-point scale. Total score for each movement (maximum of nine) and overall score (maximum of 63) were used as criteria. Multivariate analysis of variance (MANOVA) was used to test the effect of developmental group (three levels) on the criteria. Receiver operating curves were built to examine the discriminant capability of the overall score. A significant effect of developmental group was noted, with the U18 sample having a lower mean total score for four of the five movements. Overall scores of 49/63 and 50/63 discriminated the elite U18 sample from Group 1 and Group 2, respectively. U18 players may have less developed athletic movement skills when compared to their senior AFL counterparts.     

Measurement of total energy expenditure by the doubly labelled water method in professional soccer players

To determine the daily energy requirements of professional soccer players during a competitive season, we measured total energy expenditure in seven players (age 22.1+/-1.9 years, height 1.75+/-0.05 m, mass 69.8+/-4.7 kg; mean +/- s) using the doubly labelled water method. Energy intake was simultaneously estimated from 7 day self-report dietary records. Mean total energy expenditure and energy intake were 14.8+/-1.7 MJ x day(-1) (3532+/-408 kcal x day(-1)) and 13.0+/-2.4 MJ x day(-1) (3113+/-581 kcal x day(-1)), respectively. Although there was a significant difference between total energy expenditure and energy intake (P < 0.01), there was a strong relationship between the two (r= 0.893, P< 0.01). Basal metabolic rate and recommended energy allowance calculated from the Recommended Dietary Allowances for the Japanese were 7.0+/-0.3 MJ x day(-1) (1683+/-81 kcal x day(-1)) and 15.6+/-0.8 MJ x day(-1) (3739+/-180 kcal x day(-1)), respectively. A physical activity level (total energy expenditure/ basal metabolic rate) of 2.11+/-0.30 indicated that, during the competitive season, professional soccer players undertake much routine physical activity, similar to that of competitive athletes during moderate training. Energy intake estimated using dietary records was under-reported, suggesting that its calculation from these data does not predict energy expenditure in soccer players.     

Single Functional Movement Screen items as main predictors of injury risk in amateur male soccer players

The Functional Movement Screen (FMS) has been applied to identify predisposed players, mainly in professional sports, and their injury risk. Empirical evidence on the FMS in amateur soccer is scant. Furthermore, the composite FMS score contains upper, lower, and core-related body items, which might be related differently in soccer-specific injury incidences. The aim of this study was twofold: to investigate the relationship between the composite FMS score and the injury incidence of amateur soccer players and to analyze the contribution of single FMS test items to the injury state. In all, 83 amateur male soccer players (23?±?4 years old) were evaluated using the FMS prior to the preparation period of the 2016/2017 season. Injuries (lower extremities, non-contact, time loss) were continuously documented throughout the first competition period. The composite FMS score differed significantly (p?=?0.017) between injured (15.1?±?2.5) and non-injured (16.5?±?2) players. A twofold increase in the risk of injury was found for a composite FMS score of 14 or less. Significant correlations between single test items with a score?≤?2 and injured players were found for the trunk stability push-up exercise (χ²?=?17.4, df?=?1, p?<?0.001, φ?=?0.5) and the rotary stability exercise (χ²?=?6.7, df?=?1, p?=?0.009, φ?=?0.3). The composite FMS score seems to be an indicator of injury risk in amateur soccer with injured players having lower core stability and lower core strength.     

Mission Statements and Cake Stalls: The Women’s Supporter Group in Australian Football League Clubs

ABSTRACT

The Australian Football League (AFL) has made extensive efforts in the past decade to ensure that Australian Rules football is seen as an inclusive culture that respects, acknowledges, and desires the presence of female supporters in its membership base. Given that women have constituted a significant proportion of the football audience since the inception of the game in the mid-1800s, this show of support for women would appear to be belated and leads one to question what other motivations lie behind it. This article questions whether these recent attempts to acknowledge women as an important constituent group in AFL football culture, through the formation and/or maintenance of dedicated female supporter groups and networks in AFL football clubs, are genuinely aimed at making AFL club culture more inclusive of women.     

Injuries during football tournaments in 45,000 children and adolescents

Four percent of the world’s population, or 265 million people, play football, and many players are injured every year. The present study investigated more than 1800 injuries in over 45,000 youth players participating in three consecutive international football tournaments in Denmark in 2012–2014. The aim was to investigate the injury types and locations in children and adolescent football players and the differences between genders and age groups (11–15 and 16–19 years of age). An overall injury rate of 15.3 per 1000 player hours was found. The most common injury location was lower extremities (66.7%), and the most common injury type was contusion (24.4%). Girls had a relative risk of injury of 1.5 compared with boys, p?p?p?相似文献   

Science and Gaelic football: A review

This review focuses on Gaelic football and scientific reports of the characteristics of its players and the demands of the game. Anthropometric characteristics vary according to positional role, but top players display high muscularity and good all-round fitness at the peak of the competitive season. Match analysis indicates that exercise intensity is roughly equivalent to that for professional soccer. Average heart rates are approximately 160 beats· min-1 during competitive matches, and average oxygen consumption is about 72% of maximum. Metabolic fatigue in active muscles is unlikely. Conventional biomechanical and electromyographic techniques are useful in gaining insight into individual games skills. Inadequate attention has been given to injury prevention and to psychological aspects of the game. Although possessing unique characteristics, Gaelic football has many similarities with other football codes, especially Australian Rules football where the ball is played by both hands and feet and where tackling is permitted.     

Bilateral leg extension power and fat-free mass in young oarsmen

We evaluated the impact of bilateral leg extension power and fat-free mass on 2000 m rowing ergometer performance in 332 young oarsmen (age 21+/-2 years, height 1.76+/-0.05 m, body mass 62+/-6 kg; mean+/-s). The 2000 m rowing performance time was correlated with height (1.62-1.93 m; R2=0.23, P<0.001), body mass (53-95 kg; R2=0.53, P<0.001), fat-free mass (47-82 kg; R2=0.58, P<0.001) and bilateral leg extension power (1202-3302 W; R2=0.38, P<0.001). Multiple regression analysis selected fat-free mass and bilateral leg extension power as regressor variables. Fat-free mass explained 58% of the variability in rowing performance and the inclusion of bilateral leg extension power improved the power of prediction by 5%. The results suggest that rowing involves almost every muscle in the body and that bilateral leg extension power is very important during this activity.     

The relationship between mechanical stiffness and athletic performance markers in sub-elite footballers

This study investigated the relationship between several measures of lower-body stiffness and physical performance variables in 22 sub-elite male football players (mean ± SD; 21.9 ± 1.5 yr; 1.79 ± 0.06 m; 72.2 ± 7.2 kg). The participants were assessed for individual muscle stiffness of the Rectus Femoris (RF), Biceps Femoris (BF) and Medial Gastrocnemius (MG) muscles and vertical stiffness (Kvert) was also assessed assessed running acceleration, maximal sprint speed, agility, vertical jumping and muscular strength. Pearson’s correlations quantified the relationships and participants were also separated into relatively stiff (SG) and compliant groups (CG) for each variable. When ranked by Kvert the SG exhibited superior performance during sprinting, agility, jumping and strength (p ≤ 0.05) and when ranked by RF stiffness, SG exhibited superior sprint, agility and drop jump performance (p ≤ 0.05), while MG and BF stiffness were not related to performance. Higher stiffness appears to be beneficial to athletic performance for football players and therefore it may be beneficial for practitioners working with athletes that are required to perform dynamic activities to consider the contribution of stiffness to athletic performance.     

Groin injuries in professional rugby league players: a prospective study

Altogether, 100 uninjured professional rugby league players were evaluated over a 2-year period. Their height, body mass, sum of skinfolds, girths and bone diameters were recorded. A Cybex 340 isokinetic dynamometer was used to determine peak torque, work, power, endurance ratios and peak torque ratios of the hip abductors and adductors (5 repetitions at 0.52 and 2.08 rad?·?s^??1; 20 repetitions at 3.66 rad?·?s^??1) and knee flexors and extensors (4 repetitions at 1.04 and 3.14 rad?·?s^??1; 30 repetitions at 5.22 rad?·?s^??1). Hip abduction and adduction were also assessed with the hip in external rotation. Discriminant function analysis was conducted on all predictor variables to develop a multivariate predictive model capable of classifying players with a high degree of accuracy into groups with and without a groin injury. The model consisted of eight variables and correctly classified 91.7% of the non-injured players and 90.5% of the injured players. The correct classification for the model as a whole was 91.4%. The aetiological factors identified as being related to injury of the groin musculotendinous unit included abduction and adduction-with-rotation peak torque, angle of adduction and abduction-with-rotation peak torque, strength ratio of hip muscle groups, bilateral difference in extension peak torque, femur diameter and body mass.     

A comparison of the activity demands of elite and sub-elite Australian men's basketball competition

The purpose of the study was to describe the differences in the activity demands of sub-elite and elite Australian men's basketball competition. Ten elite (age 28.3 ± 4.9 years, mass 97.0 ± 13.9 kg, height 197.4 ± 8.3 cm) and 12 sub-elite (age 26.1 ± 5.3 years, mass 85.9 ± 13.2 kg, height 191.4 ± 7.6 cm) Australian basketball players participated in the study. Player activity was analysed using video-based time-motion analysis across multiple in-season matches. Customized analytical software was used to calculate player activity into frequencies, mean and total durations (s), and mean and total distances (m) for standing/walking, jogging, running, sprinting, low shuffling, high shuffling, and dribbling movements. Only movement frequency was calculated for jumping and upper body activity. Multivariate analysis of variance revealed that elite players performed significantly more total movement changes (P <0.001), and experienced greater activity workloads while jogging (P <0.01) and running (P <0.002). In contrast, sub-elite players performed significantly more standing/walking (P <0.023) and sprinting (P <0.003) activities. These data suggest that elite basketball competition requires a greater intermittent workload and more sustained activity demands, whereas sub-elite competition may involve greater bursts of activity and longer recovery periods. These differences are likely to reflect variations in player skill and fitness, as well as playing structure between playing standards.     

Ground reaction forces and knee mechanics in the weight acceptance phase of a dance leap take-off and landing

Aesthetic constraints allow dancers fewer technique modifications than other athletes to negotiate the demands of leaping. We examined vertical ground reaction force and knee mechanics during a saut de chat performed by healthy dancers. It was hypothesized that vertical ground reaction force during landing would exceed that of take-off, resulting in greater knee extensor moments and greater knee angular stiffness. Twelve dancers (six males, six females; age 18.9 ± 1.2 years, mass 59.2 ± 9.5 kg, height 1.68 ± 0.08 m, dance training 8.9 ± 5.1 years) with no history of low back pain or lower extremity pathology participated in the study. Saut de chat data were captured using an eight-camera Vicon system and AMTI force platforms. Peak ground reaction force was 26% greater during the landing phase, but did not result in increased peak knee extensor moments. Taking into account the 67% greater knee angular displacement during landing, this resulted in less knee angular stiffness during landing. In conclusion, landing was accomplished with less knee angular stiffness despite the greater peak ground reaction force. A link between decreased joint angular stiffness and increased soft tissue injury risk has been proposed elsewhere; therefore, landing from a saut de chat may be more injurious to the knee soft tissue than take-off.     

The efficacy of talent selection criteria in the Australian Football League

ABSTRACT

This study investigated the association between talent selection criteria, draft order and match performance in professional Australian Football players. Physical performance results from the Australian Football League (AFL) National Draft combine and non-performance based talent selection criteria were collated for all players drafted in the National Draft with selections 1–80 between 2003 and 2008 (n = 318). Match performance was assessed via the AFL Player Ranking metric that was provided by a commercial statistical provider (Champion Data Pty Ltd). A combination of stepwise multiple regression and linear mixed model analyses examined the influence of National Draft combine physical performance assessments and non-performance based talent selection criteria on draft order and future match performance. Earlier draft selection was associated with Under-18 all Australian team selection, height, Under-18 National Championship participation and indigenous status. The 20 m sprint and state of origin were associated with later draft selection. Under-18 all Australian team selection increased both Player Ranking/game and total Player Ranking. Under-18 all Australian team selection displays efficacy for selecting players with the potential for success.     

Kinetic comparison of a side-foot soccer kick between experienced and inexperienced players

The aim of this study was to identify critical kinetic variables that lead to increased ball velocity during a side-foot passing kick in soccer. Seven experienced male soccer players and eight inexperienced players participated in the experiment. They were instructed to perform side-foot kicks along the ground with maximum effort with an eye on the target line. The joint angles, angular velocities, and torques of the kicking leg were determined based on the three-dimensional kinematic data. The mean ball speed of the experienced group (21.4 +/- 1.5 m/s) was significantly faster than that of the inexperienced group (16.0 +/- 1.0m/s; P < 0.001). The motions of the inexperienced players tended to be less dynamic than those of the experienced players. The most noticeable difference in the kinetics of the kick was found in the hip flexion torque throughout the back-swing phase until the leg-cocking phase. The mean peak value of the experienced group (168 +/- 20 N x or m) was significantly greater than that of the inexperienced group (94 +/- 17 N x or m; P < 0.001). To increase ball speed during a side-foot passing kick, the generation of hip-flexion torque during the earlier stage of kicking is critical.