Individual and combined effects of acute and chronic running loads on injury risk in elite Australian footballers.

A model that takes into account the current workload, and the workload the athlete has been prepared for, as an acute:chronic workload ratio has been previously used as a novel way to monitor training load and injury risk. Fifty-nine elite Australian football players from one club participated in this 2-year study. Global Positioning System technology was used to provide information on running workloads of players. An injury was defined as any non-contact "time-loss" injury. One-week (acute), along with 4-week (chronic) workloads were calculated for a range of variables. The size of the acute workload in relation to the chronic workload was calculated as an acute:chronic workload ratio. An acute:chronic workload ratio of >2.0 for total distance during the in-season was associated with a 5 to 8-fold greater injury risk in the current [relative risk (RR) = 8.65, P = 0.001] and subsequent week (RR = 5.49, P = 0.016). Players with a high-speed distance acute:chronic workload ratio of >2.0 were 5-11 times more likely to sustain an injury in the current (RR = 11.62, P = 0.006) and subsequent week (RR = 5.10, P = 0.014). These findings demonstrate that sharp increases in running workload increase the likelihood of injury in both the week the workload is performed, and the subsequent week.

Influence of Strength, Sprint Running, and Combined Strength and Sprint Running Training on Short Sprint Performance in Young Adults.

The purpose of this study was to assess the degree of transference of 6 weeks of full squat vs. full squat plus sprint running training to short (ranged from 0-10 to 0-30 m) sprint running performance in non-athletes. We hypothesized that a speed-full-squat training regimen could enhance squat strength and power with simultaneous improvements in short sprint performance. 122 physically active adults (age: 20.5±2.5 years; body mass: 65.8±6.1 kg; height: 1.71±0.08 m) were randomly divided into 4 groups: full squat training (n=36), combined full squat and sprint training (n=32), speed training only (n=34) and non-training control group (n=20). Each training group completed 2 sessions per week over 6 weeks, while the control group performed only their normal physical activity. Sprint performance was improved after sprint running or full squat training alone (1.7% and 1.8% P<0.05, respectively), however larger enhancements (2.3%; P<0.01) were observed after the combined full squat plus sprint training intervention. These results suggest that in recreationally active adults, combined full squat and sprint training provides a greater stimulus for improving sprint performance than either modality alone.

Activity Profiles of Successful and Less-successful Semi-elite Rugby League Teams.

This study investigated whether match intensities during predefined periods differed among successful and less-successful rugby league teams. 4 semi-elite rugby league teams were split into 'high-success' and 'low-success' groups based on their success rates. Movement was recorded using a global positioning system (10 Hz) during 20 rugby league matches. Following the peak ball-in-play time period, the high-success group was able to maintain ball-in-play time that was: (1) 22% greater than the low-success group (P=0.01) and (2) greater than their mean period of match-play (P=0.01). In the peak and mean periods of match play, hit-up forwards from the high-success group covered less total distance (P=0.02; P=0.01), less high-intensity running distance (P=0.01; P=0.01) and were involved in a greater number of collisions (P=0.03; P=0.01) than hit-up forwards from the low-success group. These results demonstrate that greater amounts of high-intensity running and total distance are not related to competitive success in semi-elite rugby league. Rather, competitive success is associated with involvement of hit-up forwards in a greater number of collisions and the ability of high-success teams to maintain a higher ball-in-play time following the peak period. Strength and conditioning programs that: (1) emphasize high-intensity running and neglect to combine these running demands with collisions, and (2) do not offer exposure to match specific ball-in-play time demands, may not provide sufficient physiological preparation for teams to be successful in rugby league.

Association of anthropometric qualities with vertical jump performance in elite male volleyball players.

AIM: The objective of this study was to examine the association between physical and anthropometric profiles and vertical jump performance in elite volleyball players. METHODS: Thirty-three elite male volleyball players (21±1 y, 76.9±5.2 kg, 186.5±5 cm) were studied. Several anthropometric measurements (body mass, stature, body mass index, lower limb length and sitting height) together with jumping height anaerobic power of counter movement jump with arm swing (CMJarm) were obtained from all subjects. Forward stepwise multiple linear regression analysis was performed to determine if any of the anthropometric parameters were predictive of CMJarm. RESULTS: Anaerobic power was significantly higher (P≤0.05) in the tallest players relative to their shorter counterparts. A significant relationship was observed between CMJarm and lower limb length (r2=0.69; P<0.001) and between the lower limb length and anaerobic power obtained with CMJarm (r2=0.57; P<0.01). While significantly correlated (P≤0.05) with CMJarm performance, stature, lower limb length/stature and sitting height/stature ratios were not significant (P>0.05) predictors of CMJarm performance. CONCLUSION: This study demonstrates that lower limb length is correlated with CMJarm in elite male volleyball players. The players with longer lower limbs have the better vertical jump performances and their anaerobic power is higher. These results could be of importance for trained athletes in sports relying on jumping performance, such as basketball, handball or volleyball. Thus, the measurement of anthropometric characteristics, such as stature and lower limb length may assist coaches in the early phases of talent identification in volleyball.

Physiological and anthropometric characteristics of starters and non-starters in junior rugby league players, aged 13-17 years.

AIM: The purpose of this study was to investigate the physical qualities of junior rugby league players (Under 14, 16, and 18) and determine if preseason fitness measures were significantly different for the players selected to play in the first competitive game of the season (i.e. starters) compared to the players not selected (i.e. non-starters). METHODS: Eighty-eight junior (N.=53 Under 14; N.=20 Under 16; N.=15 Under 18) subelite rugby league players participated in this study. All players were registered with the same junior recreational rugby league club. Subjects underwent measurements of anthropometry (height, body mass, and sum of four skinfolds), speed (10-m, 20-m, and 40-m sprint), change of direction speed (505 test), estimated lower body power (vertical jump), and estimated maximal aerobic power (multi-stage fitness test) at the beginning of the competitive season. RESULTS: While the relative importance of the different physical qualities differed between playing levels, starters tended to be taller, have faster change of direction speed, and greater playing experience than non-starters. Moderate to large effect size differences were detected between starters and non-starters for speed and estimated maximal aerobic power results. CONCLUSIONS: These findings demonstrate that junior rugby league players selected to the starting team have better developed physical qualities than non-starting players. Coaches should emphasise the development of speed, change of direction speed, and aerobic qualities in junior rugby league players.

Epidemiological studies of injuries in rugby league: suggestions for definitions, data collection and reporting methods.

Studies on rugby league injuries use a variety of definitions and methodologies. Consequently, comparisons of published studies are difficult. Researchers with an interest in understanding the epidemiology of rugby league injury participated in a majority agreement process. This paper provides suggestions for the definitions, data collection and reporting methods for future studies of rugby league injuries. The proposed methods and definitions were developed through the use of a majority agreement process on draft versions by all authors. Recommended definitions for injury incidence, recurrence, severity and match exposure are provided as well as injury site, type, diagnosis and causation. Suggestions for match and training injury incidence calculations are also provided for the purposes of comparison. This paper provides standard definitions that, if utilised, will enable meaningful comparison of future rugby league injury surveillance data from different countries and playing levels.

Training injuries in New Zealand amateur rugby league players.

This study investigated the incidence, site, nature and severity of training injuries in a New Zealand amateur rugby league team. The incidence of injuries was prospectively studied in a senior amateur rugby league club over one domestic season. All injuries sustained during training sessions were recorded. Injury data was collected from a total of 77 training sessions. Information recorded included the date, time, site, nature, cause and severity of injury. A total of 66 training injuries were recorded. The total injury incidence was 22.4 per 1000 training hours. Injuries resulting in missed training sessions were 16.9 per 1000 h. The most common injury site was the thigh for both overall injuries and injuries resulting in missed training weeks. The incidence of overexertion injuries peaked immediately prior to the commencement of the competitive season. The high rates of overexertion injuries suggest that an increase in intensity may contribute to training injuries in amateur rugby league players. An understanding of the demands of training, and the effects that injuries have on players is essential for the identification of injury prevention strategies.

Incidence of injuries in the New Zealand national rugby league sevens tournament.

This study investigated the incidence, site, nature and causes of injuries sustained in the New Zealand national rugby league sevens tournament. A total of 218 players competing in 47 matches were studied. All injuries sustained within the tournament were prospectively recorded. Injuries were categorised according to the severity assessment at the time of the injury. Information obtained included the time, site, nature and cause of the injury. The incidence of injury was 497.6 per 1000 playing hours. More than 40% (216.1 per 1000) of injuries sustained occurred within the lower limbs. The shoulder was the single most commonly injured site (78.6 per 1000). Sprains were the most common injury type (189.9 per 1000). The ball-carrier sustained significantly more (p<0.05) injuries than the tackling player (216.1 per 1000 [43.4%] versus 117.8 per 1000 [23.7%]). There were significantly more injuries on the first day of competition than on the second day of competition (600.4 per 1000 [76.3%] versus 320.9 per 1000 [23.7%]). The findings of higher injury rates on the first day of competition and during the second period of matches suggest that playing intensity and player fatigue may contribute to injuries in rugby league sevens.

A comparison of physiological and anthropometric characteristics among playing positions in junior rugby league players.

OBJECTIVES: To compare the physiological and anthropometric characteristics of specific playing positions and positional playing groups in junior rugby league players. METHODS: Two hundred and forty junior rugby league players underwent measurements of standard anthropometry (body mass, height, sum of four skinfolds), muscular power (vertical jump), speed (10, 20, and 40 m sprint), agility (L run), and estimated maximal aerobic power (multi-stage fitness test) during the competitive phase of the season, after players had obtained a degree of match fitness. RESULTS: Props were significantly (p<0.05) taller, heavier, and had greater skinfold thickness than all other positions. The halfback and centre positions were faster than props over 40 m. Halfbacks had significantly (p<0.05) greater estimated maximal aerobic power than props. When data were analysed according to positional similarities, it was found that the props positional group had lower 20 and 40 m speed, agility, and estimated maximal aerobic power than the hookers and halves and outside backs positional groups. Differences in the physiological and anthropometric characteristics of other individual playing positions and positional playing groups were uncommon. CONCLUSIONS: The results of this study demonstrate that few physiological and anthropometric differences exist among individual playing positions in junior rugby league players, although props are taller, heavier, have greater skinfold thickness, lower 20 and 40 m speed, agility, and estimated maximal aerobic power than other positional playing groups. These findings provide normative data and realistic performance standards for junior rugby league players competing in specific individual positions and positional playing groups.

Influence of the limited interchange rule on injury rates in sub-elite Rugby League players.

This study investigated the incidence of injury in sub-elite Rugby League players before and after the introduction of the limited interchange rule. The incidence of injury was prospectively studied in one sub-elite Rugby League club over three competitive seasons. Two seasons were played under the unlimited interchange rule, while the third season was played under the limited interchange rule. Players participated in 91 matches under the unlimited interchange rule and 44 matches under the limited interchange rule. Injury was defined as any pain, disability or injury that occurred as a result of a competition game that caused the player to miss a subsequent game. The relative risk (RR) of injury significantly decreased (RR = 0.70 [0.65 to 0.75], P<0.05) following the introduction of the limited interchange rule, with the incidence of injury decreasing from 72.5 (58.2 to 86.8) per 1000 playing hr under the unlimited interchange rule to 51.0 (33.8 to 68.1) per 1000 playing hr under the limited interchange rule. The risk of sustaining thigh and calf injuries (RR= 0.27 [0.12 to 0.59], P < 0.05), muscular strains (RR= 0.23 10.17 to 0.31]., P<0.05), and high intensity running injuries (RR= 0.16 [0.04 to 0.691, P<0.05) was significantly reduced following the introduction of the limited interchange rule. These findings demonstrate that the risk of injury in sub-elite Rugby League players is significantly reduced following the introduction of the limited interchange rule. The reduced injury risk may reflect a fatigue-induced reduction in match speed and impact forces associated with physical collisions and tackles.

Reductions in pre-season training loads reduce training injury rates in rugby league players.

OBJECTIVES: To investigate if reductions in pre-season training loads reduced the incidence of training injuries in rugby league players, and to determine if the reductions in training loads compromised the improvements in physical fitness obtained during the pre-season preparation period. METHODS: A total of 220 sub-elite rugby league players participated in this 3 year prospective study. Players underwent measurements of speed, muscular power, and maximal aerobic power before and after three 4 month (December to March) pre-season preparation periods (2001-2003). A periodised skills and conditioning program was implemented, with training loads progressively increased in the general preparatory phase of the season (December to February) and reduced slightly in March in preparation for the competitive phase of the season. Training loads were calculated by multiplying the training session intensity by the duration of the training session. Following the initial season (2001), training loads were reduced through reductions in training duration (2002) and training intensity (2003). The incidence of injury was prospectively recorded over the three pre-season periods. RESULTS: The training loads for the 2002 and 2003 pre-season periods were significantly lower (p<0.001) than those in 2001. The incidence of injury was significantly higher in the 2001 pre-season than the 2002 and 2003 pre-season periods. The increases in maximal aerobic power progressively improved across the three seasons with a 62-88% probability that the 2002 and 2003 pre-season improvements in maximal aerobic power were of greater physiological significance than the 2001 pre-season improvements in maximal aerobic power. CONCLUSIONS: These findings demonstrate that reductions in pre-season training loads reduce training injury rates in rugby league players and result in greater improvements in maximal aerobic power.

Influence of injuries on team playing performance in Rugby League.

All injuries have the potential to impact on individual sporting performance and as a result may influence team playing performance. However, the influence of injuries on team playing performance is unclear. The purpose of this study was to investigate the influence of injuries on team playing performance in Rugby League. All injuries sustained by one semi-professional first grade Rugby League team were prospectively studied during the 2001 competitive season. An injury was defined as any pain or disability suffered by a player during a match. Team playing performance for each match was estimated from the metres gained while in possession of the football, points scored, points conceded, the final points differential and the completion rates of attacking sets of tackles. A total of 294 injuries were recorded. The average metres gained for all matches was 1471 (95% confidence interval, CI: 1383 to 1559) m. The team averaged 42 (95% CI: 32 to 51) points in attack each match and conceded an average of 15 (95% CI: 9 to 21) points in defence. The average completion rate for the season was 65.3 (95% CI: 60.6 to 70.0)%. There was no significant association (p>0.05) between the number of injuries sustained and team-playing performance. These findings suggest that injuries have minimal impact on team-playing performance in Rugby League. Further research on a larger sample (including winning and losing teams), is required to provide a detailed analysis of the influence of injuries on team playing performance in Rugby League.

Incidence of injury in semi-professional rugby league players.

OBJECTIVES: To investigate the site, nature, cause, and severity of injuries in semi-professional rugby league players. METHODS: The incidence of injury was prospectively studied in one hundred and fifty six semi-professional rugby league players over two competitive seasons. All injuries sustained during matches and training sessions were recorded. Injury data were collected from a total of 137 matches and 148 training sessions. Information recorded included the date and time of injury, site, nature, cause, and severity of injury. RESULTS: During the two seasons, 1,694 playing injuries and 559 training injuries were sustained. The match injury incidence was 824.7 per 1,000 player-position game hours and training injury incidence was 45.3 per 1,000 training hours. Over 20% of the total training (17.4 per 1,000) and playing (168.0 per 1,000) injuries sustained were to the thigh and calf. Muscular injuries (haematomas and strains) were the most common type of injury sustained during training (22.0 per 1,000, 48.7%) and matches (271.7 per 1,000, 32.9%). Playing injuries were most commonly sustained in tackles (382.2 per 1,000, 46.3%), while overexertion was the most common cause of training injuries (15.5 per 1,000, 34.4%). The majority of playing injuries were sustained in the first half of matches (1,013.6 per 1,000, 61.5% v 635.8 per 1,000, 38.5%), whereas training injuries occurred more frequently in the latter stages of the training session (50.0 per 1,000, 55.3% v 40.5 per 1,000, 44.7%). Significantly more training injuries were sustained in the early half of the season, however, playing injuries occurred more frequently in the latter stages of the season. CONCLUSIONS: These results suggest that changes in training and playing intensity impact significantly upon injury rates in semi-professional rugby league players. Further studies investigating the influence of training and playing intensity on injuries in rugby league are warranted.

Physiological characteristics of junior and senior rugby league players.

OBJECTIVES: To investigate the physiological characteristics of subelite junior and senior rugby league players and establish performance standards for these athletes. METHODS: A total of 159 junior (under 16, 15, 14, and 13, n = 88) and senior (first grade, second grade, and under 19, n = 71) rugby league players (forwards, n = 80, backs, n = 79), competing at a subelite level, underwent measurements of body mass, muscular power (vertical jump), speed (10 m, 20 m, and 40 m sprint), agility (Illinois agility run), and estimated maximal aerobic power (multistage fitness test). Data were also collected on match and training frequency and playing experience. RESULTS: There was a significant effect (p<0.05) of age and playing level on playing experience, body mass, muscular power, speed, agility, and estimated maximal aerobic power, with the physiological capacities of players increasing as the playing level increased. Forwards were heavier than backs for all junior and senior teams. Forwards and backs had similar estimated maximal aerobic power, except for under 16 players, for whom significant (p<0.05) differences were detected (mean (95% confidence intervals) 42.9 (40.1 to 45.7) v 49.5 (46.4 to 52.6) ml/kg/min for forwards and backs respectively). Scores for speed, muscular power, and agility were not significantly different between forwards and backs for any of the junior or senior teams. CONCLUSIONS: The results show that there is a progressive improvement in the physiological capacities of rugby league players as the playing level increases. These findings provide normative data and performance standards for subelite junior and senior rugby league players. Further studies on the sociological, physical, psychological, and personal predictors of talent in rugby league are warranted.

Incidence of injury in amateur rugby league sevens.

OBJECTIVES: To investigate the incidence, site, and nature of injuries sustained in amateur rugby league sevens tournaments. METHODS: A total of 168 players competing in three amateur rugby league sevens tournaments were studied. All injuries sustained during matches were recorded. Information recorded included the name of the injured player and the time, cause, anatomical site, and nature of the injury. RESULTS: The incidence of injury was 283.5 per 1000 playing hours. Some 40% (113.4 per 1000 playing hours) of all injuries sustained were to the lower limb (chi(2) = 5.3, df = 1, p<0.05). Contusions were the most common type of injury (113.4 per 1000 hours, 40%, chi(2) = 9.5, df = 4, p<0.05), with most (198.4 per 1000 hours, 70%, chi(2) = 31.5, df =4, p<0.001) occurring in physical collisions and tackles. An increasing injury incidence was observed over the first (99.2 per 1000 hours), second (198.4 per 1000 hours), third (347.2 per 1000 hours), and fourth (694.4 per 1000 hours) matches played during the tournaments (chi(2) = 9.2, df = 3, p<0.05). CONCLUSIONS: The results of this study suggest that amateur rugby league sevens tournaments, which require players to compete repeatedly on the same day, may hasten the onset of fatigue and predispose to injury.

Reproducibility of ventilation of thresholds in trained cyclists during ramp cycle exercise.

The reproducibility of peak cardiopulmonary exercise responses and the first (VT1) and second [VT2) ventilation thresholds was studied in sixteen endurance-trained male cyclists (mean +/- SD peak oxygen uptake [VO2 peak] = 63.3 +/- 7.1 ml x kg(-1) x min(-1)) during duplicate 30 W x min(-1) ramp cycling protocols. Expired gas sampled from a mixing chamber was analysed on-line and VT1 and VT2 were determined by computerised V-slope analysis and visually by two evaluators (test-retest reliability) and again by one of the evaluators 12 months later (intra-evaluator reliability) from 20-s-average respiratory data. The results demonstrated high intra-evaluator reliability (r = 0.91-0.97, P < 0.0001) for repeat determinations of VO2, work rate (WR) and heart rate (HR) at VT1 and VT2. No significant differences were observed between Tests 1 and 2 for any of the measured variables (P > 0.05). Test-retest intraclass reliability coefficients ranged from 0.86 to 0.98 (P < 0.0001) for VO2 peak, peak pulmonary ventilation (VE), carbon dioxide output (VCO2), HR and WR values, and measurements of VO2 and WR at VT2, and from 0.67 to 0.80 (P < 0.01) for measurements of VO2 and WR at VT1. The reliability of VT1 and VT2 was reduced when the thresholds were expressed as relative (%VO2 peak) (r = 0.67-0.70, P<0.01) rather than absolute (l x min(-1)) (r = 0.77-0.93, P<0.001) VO2 values. It was concluded that VO2 peak, peak VE, VCO2. HR and WR values, and VT2 are highly reproducible in trained cyclists using a 30 W x min(-1) ramp exercise function. However, determinations of VT1 are less reliable. Additionally, ventilation thresholds are more reliably described using absolute rather than relative VO2 values.

Does endurance training affect orthostatic responses in healthy elderly men?

PURPOSE: To investigate the effects and time course of endurance training on the regulation of heart rate (HR), arterial pressure (AP), norepinephrine (NE), and plasma volume (PV) during orthostatic stress in healthy elderly men. METHODS: Thirty-one healthy men (65--75 yr) were randomly allocated into endurance training (N = 20, EX) and control (N = 11, CON) groups. The EX group cycled 3 d x wk(-1) for 30 min at 70% VO(2peak) for 12 wk x VO(2peak) was determined on an electronically braked cycle ergometer, before training and after 4, 8, and 12 wk of endurance training. The immediate (initial 30 s), early steady-state (1 min), and prolonged (5, 10, 15 min) beat-by-beat HR and AP responses during 90 degrees head-up tilt (HUT) were measured at least 3 d after each VO(2peak) test. Spontaneous baroreflex slopes were determined by application of linear regression to sequences of at least three cardiac cycles in which systolic blood pressure (SBP) and R-R interval changed in the same direction. Venous blood was collected during 90 degrees HUT and analyzed for changes in plasma NE concentrations, as well as hematocrit and hemoglobin to determine changes in PV. RESULTS: Endurance training significantly (P < 0.01) increased VO(2peak) (mL x kg(-1) x min(-1)) in EX by 10 +/- 2%. The immediate, early steady-state, and prolonged HR and AP responses and spontaneous baroreflex slopes during 90 degrees HUT were not significantly different (P > 0.05) between EX and CON groups before or after 4, 8, or 12 wk of endurance training. No significant differences (P > 0.05) were observed between EX and CON groups for peak changes in PV during orthostasis before (-15.0 +/- 1.4% vs -11.9 +/- 1.3%) or after 4 (-12.2 +/- 1.0% vs -12.7 +/- 1.4%), 8 (-13.7 +/- 1.2% vs -12.4 +/- 0.7%), and 12 wk (-10.8 +/- 1.6% vs -10.6 +/- 0.6%) of endurance training, suggesting a similar stimulus presented by 90 degrees HUT in both groups. Peak changes in NE concentrations during HUT were similar (P > 0.05) between EX and CON groups before (119 +/- 23 pg x mL(-1) vs 191 +/- 36 pg x mL(-1)) and after 4 (139 +/- 29 pg x mL(-1) vs 146 +/- 25 pg x mL(-1)), 8 (114 +/- 32 pg x mL(-1) vs 182 +/- 41 pg x mL(-1)), and 12 wk (143 +/- 35 pg x mL(-1) vs 206 +/- 42 pg.mL-1) of endurance training. CONCLUSIONS: These data indicate that in healthy elderly men, improvements in VO(2peak) can occur without compromising the regulation of HR, AP, NE, and PV during orthostatic stress.

Severity and cost of injuries in amateur rugby league: a case study.

The aim of this study was to determine the severity and cost of injuries in amateur rugby league. Seventy-two amateur rugby league players aged 28 +/- 6 years (mean +/- s) were surveyed at the end of a competitive season. An injury was defined as any pain, disability or injury that occurred as a result of a competition game which caused the player to miss subsequent games. Injuries were classified as minor (one game missed), moderate (two to four games missed) and major (five or more games missed). Of the 72 questionnaires distributed, 34 (47.2%) were returned. Twenty respondents (58.8%) sustained an injury that resulted in one or more missed games. Eight injured players (40.0%) missed five or more training sessions, six of whom (30%) missed five or more games as a result of the injury. The median time lost from employment or study for all injured players was 2 days per playing injury. The respective median direct (e.g. medical expenses) and indirect (e.g. wages lost) costs associated with the injury were 28.29 pounds and 77.04 pound per playing injury. A considerable proportion of injuries sustained in the present sample of amateur rugby league players were major, resulting in a loss of training, playing and employment or study time, and these injuries were associated with significant direct and indirect economic costs. Further studies, using a larger sample, would complement the present findings in establishing the severity and cost of amateur rugby league injuries. These results suggest that prevention strategies are required to reduce the severity and cost of amateur rugby league injuries.