Journal of Science and Medicine in Sport

Editorial Board

2012-05-01

“It's just not cricket”, or is it?

Gregory S. Kolt — 2012-05-01

“What is this cricket thing”, I hear some of our readers asking. For those of our readers from countries who are not familiar with the sport of cricket, you may be quite amused by the fact that a cricket match can last for five days, with the result being a draw – “why all the effort” you are asking. Given that this issue of Journal of Science and Medicine in Sport includes two articles that relate to the sport of cricket (one on lumbar spine injuries and the other on the use of synthetic pitches and ball bounce characteristics), I thought that I should take some time to explain more about this sport for those from countries not familiar with this pursuit. Whilst not giving a history lesson, the most traditional form of the game of cricket lasts five days, and is one where two teams, each of 11 players, bowl (i.e., throw in an awkward and biomechanically unusual way) a very hard leather ball at the opposition batter, who then aims to defend their “stumps” (i.e., 3 sticks sticking up out of the ground), hit the ball as far as they can, and then run up and down a 22-yard long section of hardened grassed ground (the pitch). To paint the picture further, the game is so “gentleman like”, in addition to both teams stopping play mid-afternoon to have “tea”, the game gave birth in the 19th Century to the phrase “It's just not cricket”. As you can imagine, this refers to having something that is unjust or just plain wrong done to someone or something.

The lumbar spine of the young cricket fast bowler: An MRI study

Helen Crewe, Bruce Elliott, Gary Couanis, Amity Campbell, Jacqueline Alderson — 2011-12-26

Abstract: Objectives: To describe the prevalence and nature of lumbar spinal abnormalities in adolescent cricket fast bowlers.Design: Observational study.Methods: 46 asymptomatic fast bowlers aged 13–18 years participated in the study and were grouped into under-15 (U15), under-17 (U17) and under-19 (U19) classifications. All participants underwent magnetic resonance imaging of the lumbar spine and abnormalities of the pars interarticularis and intervertebral discs were graded according to type and severity. Other abnormalities were also noted.Results: Fifteen bowlers (33%) had at least one pars interarticularis abnormality. Six bilateral and 10 unilateral defects were identified. Of the 10 unilateral pars abnormalities, 6 occurred on the non-dominant side. Nineteen of the abnormalities occurred at the L5 vertebral level, 2 at L4 and 1 at L3. The most common type of pars abnormality was the subtotal stress fracture, which was found in 38% of bowlers aged 16 years and under. Sixteen participants (35%) were found to have degeneration of at least 1 lumbar disc and the prevalence increased with each successive age group (29% U15, 33% U17 and 43% U19). Of the 25 discs with signs of degeneration, 9 occurred at L4/5 and 7 at L5/S1. Eleven of these were classified as mild degeneration, 13 as moderate, and 1 as severe. Disc bulges were found in 33% of participants.Conclusions: Lumbar radiological abnormalities are common in asymptomatic adolescent fast bowlers. Acute bone stress reactions of the lumbar pars interarticularis are visible on magnetic resonance imaging and, in some instances, occur before the onset of activity-related pain.

Features of sports bras that deter their use by Australian women

Kelly-Ann Bowles, Julie R. Steele, Bridget J. Munro — 2011-12-21

Abstract: Objectives: This study aimed to identify features of commercially available sports bras that deter women from wearing them while participating in physical activity.Design: Study results were obtained from a self-administered mail survey, which was posted to participants after gaining their verbal consent via random telephone recruitment.Methods: Four hundred and thirteen women aged 20–35 years were recruited from New South Wales, Australia, with 267 (65%) surveys returned.Results: It was found that the shoulder straps slipping or cutting into the shoulder were the two most disliked features of current sports bras, with 23% of respondents also indicating that the shoulder straps were the first bra feature to fail. Respondents also indicated that the perceived tightness of the sports bra around the chest was a deterrent for their use.Conclusions: Although previous research has found that a correctly fitted sports bra does not impede athletic performance, further research is required to investigate sports bra shoulder strap designs to improve wearer comfort without negatively affecting the ability of a sports bra to reduce breast motion and/or associated breast pain during participation in physical activity.

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

John W. Orchard, Tim Driscoll, Hugh Seward, Jessica J. Orchard — 2011-12-26

Abstract: Objectives: To study risk factors for hamstring injury in the Australian Football League (AFL), in particular the effect of recent changes in match participation (increased use of the interchange bench) on hamstring injury.Design: Analysis of hamstring match injury statistics extracted from an injury database combined with match participation statistics extracted from a player statistics database.Methods: 56,320 player matches in the AFL over the period 2003–2010 were analyzed, in which 416 hamstring injuries occurred.Results: In a Generalized Estimating Equation (GEE) analysis accounting for clustering of different teams, significant predictors of hamstring injuries were recent hamstring injury (RR 4.16, 95% CI 3.19–5.43), past history of ACL reconstruction (RR 1.69, 95% CI 1.09–2.60), past history of calf injury (RR 1.58, 95% CI 1.37–1.82), opposition team making 60 or more interchanges during the game (RR 1.38, 95% CI 1.12–1.68) and player having made 7 or more interchanges off the field in the last 3weeks (protective RR 0.74, 95% CI 0.59–0.93).Conclusions: These findings suggest that regular interchanges protect individual players against hamstring injuries, but increase the risk of hamstring injury for opposition players. These findings can be explained by a model in which both fatigue and average match running speed are risk factors for hamstring injury. A player who returns to the ground after a rest on the interchange bench may himself have some short-term protection against hamstring injury because of the reduced fatigue, but his rested state may contribute to increased average running speed for his direct opponent, increasing the risk of injury for players on the opposition team.

The epidemiology of injury for an elite junior Australian Football cohort

2012-01-05

Abstract: Objectives: To implement an injury recording protocol in a junior elite Australian Football competition and determine the injury profile of this population.Design: Longitudinal cohort study.Methods: Players from an elite Under 18 Australian Football competition were tracked throughout one football season in terms of participation or non-participation in the football competition. Injury reporting forms were collected for all players who were not available for selection as a result of injury.Results: The cohort consisted of 532 players who provided consent for inclusion in the study (100% of players in the competition). There were 256 injuries sustained during the season. Results were standardised to a 40 man team to allow comparison with results from the Australian Football League. The injury incidence was 17.1 new injuries per club (95% CI 14.1–19.4), and prevalence 63.3 missed matches per club (95% CI 59.1–67.1). The category “Ankle joint injuries” was the most commonly reported (n=34) and “Collision with another player” was the main injury mechanism (n=75).Conclusions: The most commonly injured region in junior elite Australian Football was the ankle and collision with another player was the most common injury mechanism. As with previous reports on junior Australian Football, injury incidence was low in comparison to the senior elite competition. Defining the injury profile guides injury prevention strategies. Analysis of injury in junior elite football may provide a unique opportunity to affect both junior and senior injury rates.

How diverse was the leisure time physical activity of older Australians over the past decade?

Merom Dafna, Cosgrove Carmen, Venugopal Kamalesh, Bauman Adrian — 2011-12-26

Abstract: Objectives: Public health recommendations for older adults highlight the need to engage in a combination of aerobic, muscle strength, flexibility and balance activities. This study characterised leisure time physical activity in older Australians (≥65 years), examining the diversity in reported activitiesDesign: Cross-sectional monitoring.Methods: The Exercise Recreation and Sport Surveys (2001–2009) were combined and analysed for 22,050 elderly.Results: Walking was reported by 45.6%, of those 53% engaged exclusively in walking. Prevalent sports (i.e., >1%) were bowls (9.4%), aerobics/callisthenics exercise (9.1%), golf (7.7%), swimming (6.4%), gym work (5.2%), cycling (3.2%), tennis (2.9%), dancing (2.1%), fishing (2.0%), tai chi (1.4%), weight lifting (1.2%) and yoga (1.1%). Significant gender differences were apparent. Over time, significant increases were reported in walking, aerobic/callisthenics and gym workout in both genders. In the previous year, 32.0% of older adults participated in “nil” activity, 40.6% engaged in one activity, 19.5% and 8.0% participated in two or three or more activities, respectively. Common combinations were walking with another aerobic activity. Only 2.6% reported a combination of aerobic, balance and strength activities. Multiple-activity participation increased over the years, but declined with increasing age, education and for the most disadvantaged, compared to single-activity participation. Partially or exclusively organised participation, combined, was reported by 42.5% of older adults. Women were more likely to combine mode of participation. Geographic region was associated with multiple-activity participation and organised-only participation.Conclusions: Most elderly people engage in one activity, if at all. An increase in participation in balance enhancing activities and weight training is warranted to maximize health benefits.

Relationship between sports participation and the level of motor coordination in childhood: A longitudinal approach

2011-11-03

Abstract: Objectives: This study examined the stability of motor coordination and the relationship between motor coordination and organized sports participation over time.Design: Longitudinal design.Methods: A total of 371 children between six and nine years of age at initial testing completed a test battery measuring motor coordination in three consecutive years and a questionnaire on their club sports participation in year 1 and year 3 of testing.Results: Correlation coefficients revealed the motor coordination of children to be a highly stable factor, ranging from 0.662 (6–8 years) to 0.873 (7–9 years). Results of the Repeated Measures ANOVA indicated that children who consistently practiced sports in a club environment over the three years of testing displayed better coordination levels than children who only partially participated or did not participate in a club environment at all. Moreover, stability was further indicated as consistent sports participation over time and changes or lack thereof did not substantially influence the development of motor coordination over time. In addition, the basic level of motor coordination and the amount of club sports participation significantly predicted sports participation two years later.Conclusion: The importance of the stability of motor coordination levels in childhood and its role in determining organized sports participation may have implications for talent identification purposes as well as potential health-related benefits in childhood and throughout the lifespan.

Use of pedometers to identify less active children and time spent in moderate to vigorous physical activity in the school setting

2011-12-09

Abstract: Objectives: To examine in the context of a school day whether a pedometer, compared to an accelerometer, was an effective tool to identify children with low physical activity levels. Additionally, to characterise within the school day, patterns of variation in level and timing of activity of the most active and least active children.Design: Observational study to compare two methods (accelerometer and pedometer) of identifying less active children and intensity of activity.Method: During school hours, for three consecutive days, children (n=47, aged 8–11 years) in two classes wore an accelerometer and sealed pedometer. Accelerometers were programmed to record at 15s epochs and the number of pedometer steps taken were recorded at the end of each school day. Patterns of activity by total accelerometer counts, and with cutoffs applied, were examined against time and the number of steps taken.Results: Based on the accelerometer (>1500counts/min), the majority (68%) of children spent more than 60min in moderate to vigorous physical activity (MVPA) during the school day. Overall, time spent in MVPA was three times greater during break times compared to classroom time, with no apparent differences by class/age or gender. Total accelerometer counts and pedometer steps were correlated (r=0.60). One minute of MVPA was equivalent to 45 (95% CI 20 to 70) pedometer steps.Conclusion: The pedometer, a practical, relatively inexpensive tool, is suitable for the identification of less active children and has some utility to assess the relative intensity of activities in the context of a school day.

Physical activity levels and movement skill instruction in secondary school physical education

Dean A. Dudley, Anthony D. Okely, Wayne G. Cotton, Phil Pearson, Peter Caputi — 2011-12-15

Abstract: Objective: To determine the levels of physical activity (PA), lesson context and teacher interaction students receive during physical education (PE) in secondary schools in New South Wales, Australia.Design: Baseline cross-sectional study.Methods: Systematic direct observation of Year 7 PE classes over a six-month period. Eighty one (81) PE lessons across six schools were observed.Results: The mean (SD) percentage of class time spent in moderate to vigorous physical activity (MVPA) was 56.9% (18.7). However, only 60% of the 81 met the recommended 50% of class time spent in moderate to vigorous physical activity (MVPA). Just over 6% of class time was spent in skill instruction. Game play made up nearly half of the lesson context (44%) and teachers spent just under one-third (31%) of class time promoting PA.Conclusions: Substantial variations in the PA, lesson context and teacher interaction exist within PE. As a large proportion of classes, especially girls’ only classes, did not meet the Centers of Disease Control and Prevention (CDC) recommendation of 50% of class time in MVPA, ways need to be found to promote PA in PE classes. Levels of skill instruction and practice were well below international comparisons and may have implications for PA participation later in life. Numerous possibilities exist for improving PE in Australia as a way of improving the activity levels and experiences of our young people.

Post-match changes in neuromuscular function and the relationship to match demands in amateur rugby league matches

Rob Duffield, Alistair Murphy, Alanna Snape, Geoffrey M. Minett, Melissa Skein — 2011-12-05

Abstract: Objectives: The current study investigated the change in neuromuscular contractile properties following competitive rugby league matches and the relationship with physical match demands.Design: Eleven trained, male rugby league players participated in 2–3 amateur, competitive matches (n=30).Methods: Prior to, immediately (within 15-min) and 2h post-match, players performed repeated counter-movement jumps (CMJ) followed by isometric tests on the right knee extensors for maximal voluntary contraction (MVC), voluntary activation (VA) and evoked twitch contractile properties of peak twitch force (Pt), rate of torque development (RTD), contraction duration (CD) and relaxation rate (RR). During each match, players wore 1Hz Global Positioning Satellite devices to record distance and speeds of matches. Further, matches were filmed and underwent notational analysis for number of total body collisions.Results: Total, high-intensity, very-high intensity distances covered and mean speed were 5585±1078m, 661±265, 216±121m and 75±14mmin−1, respectively. MVC was significantly reduced immediately and 2h post-match by 8±11 and 12±13% from pre-match (p<0.05). Moreover, twitch contractile properties indicated a suppression of Pt, RTD and RR immediately post-match (p<0.05). However, VA was not significantly altered from pre-match (90±9%), immediately-post (89±9%) or 2h post (89±8%), (p>0.05). Correlation analyses indicated that total playing time (r=−0.50) and mean speed (r=−0.40) were moderately associated to the change in post-match MVC, while mean speed (r=0.35) was moderately associated to VA.Conclusions: The present study highlights the physical demands of competitive amateur rugby league result in interruption of peripheral contractile function, and post-match voluntary torque suppression may be associated with match playing time and mean speeds.

Changes in practice task constraints shape decision-making behaviours of team games players

2011-12-08

Abstract: Objectives: This study examined the effects of manipulating relative positioning between defenders (initial distance apart) on emergent decision-making and actions in a 1 vs. 2 rugby union performance sub-phase.Design: Twelve experienced youth players performed 80 trials of a 1 (attacker) vs. 2 (defenders) practice task in which the starting distance between defenders was systematically decreased.Methods: Movement displacement trajectories of participants were video recorded to obtain 2D positional data. The independent variable was the starting distance between defenders and dependent variables were: (i) performance outcome (try or tackle), (ii) mean speed of all players during performance, and (iii), time between the first crossover and the end of the trial. Repeated measures ANOVA was used to compare the effects of different starting distances on performance.Results: Shorter starting distances between defenders were associated with a higher frequency of effective tackle outcomes, lower mean speeds of all participants, and a greater time period between the first crossover and the end of the trial.Conclusions: Decision-making behaviours emerged as a function of changes in participants’ spatial location during performance. This observation supports the importance of manipulating key spatial-temporal variables in designing representative practice task constraints that induce functional player-environment interactions in team sports training.

Differences in wrist mechanics during the golf swing based on golf handicap

2011-12-12

Abstract: Objectives: Variation in swing mechanics between golfers of different skill levels has been previously reported. To investigate if differences in three-dimensional wrist kinematics and the angle of golf club descent between low and high handicap golfers.Design: A descriptive laboratory study was performed with twenty-eight male golfers divided into two groups, low handicap golfers (handicap=0–5, n=15) and high handicap golfers (handicap≥10, n=13).Methods: Bilateral peak three-dimensional wrist mechanics, bilateral wrist mechanics at ball contact (BC), peak angle of descent from the end of the backswing to ball contact, and the angle of descent when the forearm was parallel to the ground (DEC-PAR) were determined using an 8 camera motion capture system. Independent t-tests were completed for each study variable (α=0.05). Pearson correlation coefficients were determined between golf handicap and each of the study variables.Results: The peak lead arm radial deviation (5.7degrees, p=0.008), lead arm radial deviation at ball contact (7.1degrees, p=0.001), and DEC-PAR (15.8degrees, p=0.002) were significantly greater in the high handicap group.Conclusion: In comparison with golfers with a low handicap, golfers with a high handicap have increased radial deviation during the golf swing and at ball contact.

Changes in bone turnover markers during the close season in elite football (soccer) players

Richard Weiler, Richard Keen, Roger Wolman — 2011-11-07

Abstract: Objectives: Bone turnover marker changes in response to physical activity are well documented. There is, however, little information on the extent and severity of skeletal de-conditioning in athletes in response to rest periods. This study analyses changes in markers of bone resorption and bone formation during the close season within the squad of an English Football Association Championship club.Design: Evaluation was performed on the first team football squad just before the end of the 2007/2008 football season and again 8 weeks later before pre-season testing and training.Method: Bone resorption was measured by serum concentration of C-terminal telopeptide (CTx) and bone formation by serum concentration of the N-terminal propeptide of type I procollagen (PINP). Twenty football players aged from 18 to 36 years (mean 23.6 years) were included in the study.Results: The mean change in CTx during the close season was +0.14ng/ml (95% CI: 0.21 to 0.06, p=0.001). The mean change in PINP was −10.8ng/ml (95% CI: −3.9 to −17.7, p=0.004).Conclusions: In professional football players, a close season rest of 8 weeks results in an increase in bone resorption and a decrease in bone formation markers. This imbalance between formation and resorption may have negative effects on bone mass and structure. Future research should focus on understanding the many factors that could contribute to the changes found in the study during the close season.

Is the six-minute walk test appropriate for detecting changes in cardiorespiratory fitness in healthy elderly men?

2011-12-12

Abstract: Objectives: The purpose of this study was to determine whether the six-minute walk test (6-MWT) can detect changes in cardiorespiratory fitness (CRF) induced by exercise training in healthy elderly men.Design: Randomized and prospective controlled trial.Methods: Thirty-two healthy untrained men, between 65 and 75 years of age, were randomly assigned to one of three groups: control (C, n=12), endurance training (E, n=10), or concurrent training (ER, n=10). Training groups underwent 24weeks of exercise, 3 times a week. All participants were subjected to cardiopulmonary exercise testing and the 6-MWT, before and after the training period.Results: At follow-up, the E and ER groups had significantly higher peak oxygen uptake (15.0±9.1 and 12.6±10.4%, respectively) and 6-MWT distances (5.5±5.3 and 4.6±2.8%, respectively) compared to the C group. In pre-intervention (n=32), the 6-MWT distance correlated positively with (r=0.51, p=0.001) and at anaerobic threshold (r=0.39, p=0.010). On the other hand, there was no significant correlation between the changes (after–before) in the 6-MWT distance and peak (E and ER groups: r=0.38, p=0.097).Conclusions: The 6-MWT is not appropriate to evaluate changes in CRF in healthy elderly men who performed endurance and concurrent training for 24weeks.

Differences in markers of cardiovascular disease between professional football players of West-Asian and Black African descent

M.G. Wilson, B. Hamilton, A.L. Sandridge, O. Salah, H. Chalabi — 2011-12-14

Abstract: Objectives: To examine the cardiovascular risk factors of professional football players of West-Asian and Black African descent competing in the 2010/11 Qatar Stars League.Design: Ten out of twelve professional football clubs attended pre-participation screening. 100 West-Asian males from seven Gulf States and six Middle-Eastern countries and 90 Black males from seven African countries.Methods: All players were screened using the FIFA pre-competition medical assessment, incorporating a physical examination, resting 12-Lead ECG, echocardiogram, with determination of total cholesterol, high and low density lipoprotein (HDL/LDL) and triglycerides.Results: West-Asian football players had a higher prevalence of a family history (FH) of coronary heart disease (CHD) (25% vs. 12%, p=0.025) compared to Black African players predominantly due to CHD in their fathers (14% vs. 6%, p<0.05). West-Asian players had higher total cholesterol levels (4.4 vs. 4.2mmol/L, p=0.025) and lower HDL levels (1.3 vs. 1.4mmol/L, p=0.004) than Black African players; remaining significant after adjusting for a FH of CHD. Positively, all lipid levels were clinically acceptable for both ethnicities. Finally, one in eight West-Asian and one in eleven Black African football players were regular smokers.Conclusions: The prevalence of cardiovascular disease in West-Asia is increasing. This study observed clinically acceptable blood lipid profiles for both West-Asian and Black African football players. However, West-Asian players had a greater number of markers for CVD than their Black African counterparts despite being matched for physical activity levels. Targeted education with regards to diet, lifestyle and tobacco use is required for both ethnicities.

Synthetic grass cricket pitches and ball bounce characteristics

Kevin Ball, Con Hrysomallis — 2011-12-29

Abstract: The use of synthetic grass cricket pitches is becoming more common at club and sub-elite levels which constitute the majority of cricket participants but there is sparse data on ball bounce characteristics on these surfaces.Objectives: To compare the speed, angle and consistency of ball bounce on two types of synthetic cricket surfaces, the Traditional and the All-Seasons, and compare these ball bounce characteristics with published data for natural turf pitches.Design: Group-based comparison.Methods: High speed motion analysis was used to capture data from balls projected onto the cricket pitches from a bowling machine at three speeds: slow (47kmh−1), medium (72kmh−1) and fast (104kmh−1). Both ends of the cricket pitches were assessed and two types of balls were used: 2-piece and 4-piece leather cricket balls. Digitisation was used to determine the ball speed and angle pre and post bounce and then to calculate the ratios of ball speed and angle. Consistency was determined by the coefficient of variation.Results: The All-Seasons synthetic surface generated a lower speed ratio and a higher angle ratio than the Traditional synthetic surface. The speed ratio for the Traditional surface fell within the range reported for natural turf, whilst the value for the All-Seasons surface was outside the range. Both synthetic surfaces produced angle ratios greater than those for natural turf surfaces.Conclusions: Differences were detected between the different synthetic cricket surfaces and also when compared to natural turf. This variability may have implications for skill development as well as safety.

Movement patterns in rugby sevens: Effects of tournament level, fatigue and substitute players

Dean G. Higham, David B. Pyne, Judith M. Anson, Anthony Eddy — 2011-12-21

Abstract: Objectives: Understanding of the physical demands and the effects of fatigue and substitute players in rugby sevens is limited. This study quantified the differences in movement patterns between domestic and international rugby sevens tournaments, the effects of fatigue within and between matches during tournaments, and movement patterns of second half substitute players.Design: Movement patterns of 19 international-level male rugby sevens players were recorded using a Global Positioning System (GPS) device during 11 international and 16 domestic matches (n=174 files).Methods: Maximum velocity, total distance covered, distance covered in velocity zones and number of moderate and high accelerations and decelerations are reported per min of match time. Movement patterns were compared between international and domestic matches, first and second half, first and last tournament match and substitute and full-match players.Results: Substantially greater distance was covered at high velocity (∼27% at ≥6ms−1) and 4–39% more accelerations and decelerations were performed in international than domestic matches. The relative distance covered by players at velocities >2ms−1 and the number of changes in velocity were reduced by 1–16% from first to second half. Small differences were observed in activity at <5ms−1 (−8–8%) and moderate accelerations (−18%) from first to last tournament match. All movement variables were higher (2–123%) for substitute players.Conclusions: International rugby sevens competition is more intense than domestic matches. Despite reductions in work-rate within individual matches, there is little indication of accumulated fatigue over a multi-day tournament.