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players undergo rigorous conditioning to raise their fitness,skill, and strength in advance of the upcoming season (10).Injury rates in semiprofessional players have been shown toincrease gradually throughout the preseason from Decemberto March, followed by a decline through to the end of theseason. Indeed, the preseason incidence of injury at the end

of February (205.6 per 1,000 training hours) was much higherthan at the beginning of the preseason (105.2 per 1,000training hours) (9).

In addition to the effects of training duration, intensity, andload on injury occurrence, the contribution of psychologicalfactors on injury has been examined in several studies(6,19,23). Lavallee and Flint (19) investigated the contribu-tion of anxiety, mood state, and social support to injury inathletic populations and found that high tension and anxietylevels were significantly related to the injury incidence. Highlife stress has also shown be an independent and significant(odds ratio = 1.84; 95% CI 1.103.11) predictor of sportinginjuries (23). These findings were supported by Dvorak et al.

(4) who examined this relationship in 264 football playersover the course of a year.

Psychological factors, training intensity, duration, and loadare well-established, significant predictors of injury. Theparticularly high preseason injury rates warrant research. Ifthose factors that influence the incidence of injury during thepreseason training period in professional rugby league playerscan be identified, coaches may be able to modify them.

The primary aim of the present study was to examine therelationship between training load and incidence of injuryduring a preseason training period at a professional rugbyleague club. A secondary aim was to investigate the relation-ship between the players physical and psychological status

and their preseason injury rates.

METHODS

Experimental Approach to the Problem

The present study used a prospective experimental design toidentify the relationship between training load, physical andpsychological status, and injury incidence in professionalrugby league players. The club physiotherapist assessed allinjuries, and these were expressed relative to exposure hours.The injury definition (8) and experimental design (13)employed in this study were identical to other rugby leaguestudies. It was hypothesized that a significant relationshipwould be detected between training load, physical and

psychological status, and injury incidence.

Subjects

A squad of 36 National Rugby League (NRL) players wereinvolved in this study. Participants were professional rugbyleague players (i.e., participants generated their entire incomefrom their involvement in rugby league) (7), and their agesranged from 17 to 32 years. Participation in the study formedpart of the players routine training commitments. At thetime of the study, players had completed a 6-week active

off-season and returned to preseason training with an averagemaximal oxygen consumption of 53.8 6 0.6 mlkg21min21.The average NRL playing experience of the participants was55.7 6 11.3 games. All participants received a clear expla-nation of the study, and written consent was obtained.The Institutional Review Board for Human Investigation

approved all experimental procedures.Preseason training for the season was conducted over

a period of 14 weeks, beginning in early December andfinishing in mid-March. During this time, players participatedin 69 training sessions every week, except for 11 days overthe Christmas and New Year period. The duration of trainingsessions ranged from 25 to 105 minutes, and the number ofplayers at each session varied from 11 to the full squad of 36.Sessions involved general conditioning, specific speed, agility,and skills training along with upper and lower body strengthsessions in the gymnasium. Not all players were able to attendall sessions for various reasons such as illness, injury, or otherpersonal or professional commitments.

Procedures

Injury was defined as any pain or disability that occurredduring participation in a rugby league training activity thatwas sustained by a player, irrespective of the need for trainingtime loss (18).

A modified rating of perceived exertion (RPE) scalewas usedto estimate exerciseintensity(1). The scale wasexplained to theplayers on multiple occasions, and players were asked for theirRPE within 10 minutes of completing each training session.The training load from each session was then calculated bymultiplying the RPE training intensity and the duration of thesession. Rating of perceived exertion has previously been

shown to be an acceptable tool for estimating the intensity oftraining sessions, is effective for extended aerobic exercisesessions (6), and can be reliably used for resistance trainingsessions (2). When compared to heart rate and blood lactateconcentration, the RPE scale has been shown to providea valid estimate of exercise intensity (3,5,12,16). In addition,before commencing the study, we investigated the relationshipbetween heart rate and RPE, and blood lactate concentrationand RPE on a subset of subjects during typical rugby leaguetraining activities. The correlations between training heart rateand training RPE, and training blood lactate concentration andtraining RPE were 0.89 and 0.86, respectively. A subset ofplayers (n= 11) also completed 2 identical preseason training

sessions, performed 1 week apart, before the commencementof the study, to determine testretest reliability. The intraclasscorrelation coefficient for testretest reliability and typical errorof measurement for the RPE scale were 0.99 and 4.0%,respectively. Collectively, these results demonstrate that theRPE scale offers an acceptable method of quantifying trainingintensity for collision sport athletes.

Psychological data were collected on the players percep-tions relatingto sleep, food, energy,mood, and stress. Physicaldata included players perceptions of how their body was

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Training Load and Injury

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feeling physically. Each player rated how they felt in eachcategory on a scale of 110 (with 1 being extremely poor and10 being excellent), and these ratings were recordedimmediately before 2 training sessions each week. An averageweekly figure for the entire team was calculated for eachcategory throughout the preseason. The intraclass correlation

coefficient for testretest reliability and typical error ofmeasurement for the psychological data were 0.95 and 1.2%,respectively.

Statistical Analyses

Data were analyzed using SPSS 15. Normality of distributionfor each measure was tested using the KolmogorovSmirnovtest and analysis included standard descriptive statistics,paired t-tests, Spearman and Pearson correlations, and 1-wayanalysis of variance. Injury rates per 1,000 training hourswere calculated by dividing the total number of injuriesby the exposure hours and multiplying this by 1,000. Thechi-squared (x2) test was used to determine whether the

observed injury frequency was significantly different fromthe expected injury frequency. Training monotony wascalculated by multiplying the weekly training load and theSDof the weekly training load; training strain was calculatedas the product of total weekly training load and trainingmonotony. Based on an alpha level of 0.05 and a sample sizeof 36, our beta level (power) was $0.80 for detectingcorrelations of 0.85 or greater among injury, training load,and psychological data. All results are reported as means andSDs or medians with interquartile ranges.

RESULTS

Incidence of Injury

A total of 2,877.9 training hours were recorded for the playersover the entire preseason training period, with an average of221.46 44.3 exposure hours completed by the training groupeach week. A total of 20 injuries were recorded during thepreseason training period with an overall incidence of injuryof 6.9 (95% CI: 3.710.1) per 1,000 training hours.

Site of Injury

Lower body training injuries were most common (5.6 per1,000, 80%), compared to injuries to the trunk (0.7 per 1,000,10%) and upperlimbs (0.7 per 1,000, 10%). The most commontraining injury was sustained to the thigh and calf (2.4 per1,000, 35%). Injuries to the ankle (1.0 per 1,000, 15%), knee

(1.0 per 1,000, 15%), back (0.7 per 1,000, 10%), hip (0.7 per1,000, 10%), shoulder (0.3 per1,000, 5%), elbow (0.3 per 1,000,5%), and shin (0.3 per 1,000, 5%) were less common (Table 1).

Type of Injury

Inflammation injuries and sprains and strains were the mostcommon types of training injury (1.7 per 1,000, 25%). Theincidences of degenerative injuries (1.4 per 1,000, 20%),overuse injuries, hematomas, and contusions (0.3 per 1,000,5%) were low (Table 2).

TABLE 1. Site of injury during the preseason period inprofessional rugby league players.*

Site of injuryInjury

numberInjury rate(95% CI) %

Thigh and calf 7 2.4 (0.64.2) 35Ankle/foot 3 1.0 (0.02.2) 15Knee 3 1.0 (0.02.2) 15Thorax/abdomen 2 0.7 (0.01.7) 10Hip 2 0.7 (0.01.7) 10Shoulder 1 0.3 (0.01.0) 5Elbow 1 0.3 (0.01.0) 5Shin 1 0.3 (0.01.0) 5Head/neckFace

*CI = confidence intervals.Injury rate expressed per 1,000 training hours.

TABLE 2. Type of injury during the preseason periodin professional rugby league players.*

Injury type Injury number Injury rate %

Inflammation 5 1.7 (0.213.3) 25Sprains/strains 5 1.7 (0.213.3) 25Degenerative 4 1.4 (0.032.8) 20Overuse 1 0.3 (0.01.0) 5Hematoma 1 0.3 (0.01.0) 5Contusions 1 0.3 (0.01.0) 5

Other 3 1.0 (0.02.2) 15

*CI, confidence intervals.Injury rate expressed per 1,000 training hours.

TABLE 3. Average training load, monotony, andstrain, and psychological data during the preseasonperiod for professional rugby league players.*

Training variable

Training load 2,788.6 6 913.6Training monotony 3.1 6 0.6Training strain 8,729.7 6 3,710.1Exposure hours 221.4 6 44.3Total psychological data 38.7 (10)

*Data are mean 6 SD.Nonparametric data, expressed as median and

interquartile range.

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Severity of Injury

The majority (6.6 per 1,000, 60%) of training injuries weretransient, resulting in no loss in training and requiring nomodification to the training program. Only 5% of the totalinjuries resulted in the player needing more than 2 weeks torecover and resume normal training.

Relationship between Training Load, Physical and

Psychological Status, and Injury Incidence

There was no significant relationship between playerstraining loads and psychological data (r = 0.248, p = 0.414)

or the total physical and psychological status and trainingload (r = 0.216, p = 0.478). Additionally, there was nosignificant relationship between the preseason weekly injuryrate and the weekly training load (r = 0.023, p = 0.941),training monotony (r= 0.323, p= 0.281), training strain (r=0.088, p= 0.776), and total psychological data (rho = 0.501,p = 0.081). The weekly preseason team data are shownin Table 3.

The relationship between training load and injury rate isshown in Figure 1. The average weekly preseason trainingload of positional playing groups was compared to ensurethat there was no difference among the subgroups. Theadjustables playing group included the halfback, hooker,

and fullback positions, and the outside backs included thewing and center positions. The training load for the forwardswas 2,665.4 6 926.5 arbitrary units, compared with theadjustables 2,890.2 6 954.3 arbitrary units and the outsidebacks 2,809.4 6 942.3 arbitrary units. There was nosignificant difference during the preseason in the trainingloads among the positional playing groups (F = 0.190, p =0.827). The average weekly training loads for the playinggroup were significantly greater during the early preseason(3,510.9 6 641.9 arbitrary units), compared to the late

preseason (2,169.4 6 597.7arbitrary units) (F = 15.212,p= 0.002). The higher trainingloads during the first half ofthe preseason correspondedto a higher (x2 = 2.3, df = 1,

p. 0.05) injury rate (8.7 6 3.4per 1,000 training hours) incomparison to the second halfof the preseason (5.3 6 6.3 per1,000 training hours).

DISCUSSION

Thisstudy is the first to examinethe relationship between train-ing load and injury incidenceover the preseason period inprofessional rugby league play-ers. This relationship is of great

interest to many involved inrugby league, particularly coach-

ing and conditioning staff, whose aim is to find a trainingprogram that will elicit an improvement in playing perfor-mance and physical fitness without increasing the incidenceof injury (9).

In contrast to much of the related research (8,9), the presentstudy found no significant relationship between training loadand the incidence of training injuries during the 14-weekpreseason period. In addition, the majority of injuriessustained were only minor, resulting in no loss in trainingtime and no necessary modifications to the training program.Analysis did identify a trend toward higher injury rates with

greater psychological scores (rho = 0.501, p = 0.081). Thismay suggest that when players feel healthier, they can train athigher intensities, which may increase the incidence of injury.

Weekly training loads were higher during the 14-weekpreseason training period compared to the competition phaseof the season. These findings are consistent with the work ofGabbett (9,10) who also reported higher training intensitiesand durations during the preseason period.

The weekly training loads of 2,809 arbitrary units arerelatively low for professional athletes. In addition, an injuryrate of only 6.9 per 1,000 training hours was recorded, withthe majority of injuries being transient in nature. Thesefindings may indicate that training loads were adequate

to improve fitness without unduly increasing the incidence ofinjury.

The majority of injuries sustained in this study were to thelower body, which is consistent with results from previousstudies (11,15,17). Previous investigations have suggested thatmost injuries are received by the ball carrier while beingtackled (14). Most coaches will instruct players to aim tacklesaround the hips or thighs of the attacking players (24), andthis makes this area more prone to injury. Additionally, whentackles are aimed at the upper body, the arms and shoulders

Figure 1. Preseason weekly training loads and injury rates for professional rugby league players.





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can be used to defend and protect, whereas the legs are moreexposed to heavy contact.

Several factors distinguish this study from the majority ofothers that have investigated the relationship between trainingload and injury rates. None of the previous studies haveexaminedthe relationship between training loadand injury rate

in the preseason period among professional athletes; allprevious studies have examinedthe traininginjury relationshipin amateur or semiprofessional rugby league players. Withvastly different training loads, injury rates, support staff, andtraining programs, it would be difficult to compare amateurplayers (i.e., those who do not receive match payments) and

semiprofessional players (those who receive moderate re-muneration to play) to professional rugby league players, whogenerate their entire income from their involvement in rugbyleague (7). Firstly, professional players would be expected tohave a higher base level of fitness entering the preseason,compared to amateur and semiprofessional players. Higherfitness levels would enable them to exercise at higher inten-

sities and for longer periods before fatigue. It has also beenshown that well-developed maximal aerobic power offers aprotective effect against injuries in rugby league players (11).One would also expect professional rugby league players to bemore skilfull, which would potentially help them avoid certainsituations or positions that could cause injuries. Professionalsporting clubs also have a far more thorough injury preventionprogram than amateur and semiprofessional teams, witha greater emphasis on preventive strategies including flexibilityand stretching, appropriate warm-ups and cool-downs.Dietitians are often available to assist in recovery from exercise,and physiotherapists address musculoskeletal problems.

In summary, the present study found no relationship between

training load and injury rates in a cohort of professional rugbyleague players during a 14 week preseason training period.However a trend toward greater injury rates with higherpsychological scores was identified.

PRACTICAL APPLICATIONS

Monitoring training loads is critical to ensure that playersreceive a progressively overloaded periodized trainingprogram and are given adequate recovery between high-volume and high-intensity sessions. It is important for sportscientists and strength and conditioning coaches to de-termine the appropriate training loads and recovery periods

to maximize improvements without unduly increasinginjury incidence.

The increased injury rate, coupled with the higher trainingloads in the early preseason period, suggests that professional,male rugby league players returning from the off-seasonperiod may be at greater risk of training load-related injuries.Gradual increases in training loads during this period, andensuring players return to training with a minimum standardof physical fitness, may reduce the incidence of injury in thistraining period. Of interest was the spike in injury rates

toward the end of the preseason period, when training loadswerelowest. Although these results are difficult to reconcile, itis possible that increased fitness may increase trainingintensity and subsequently increase injury rates (9).

Although the present study has found no significant rela-tionship between training loads and injury rates, there was

a trend toward a higher injury incidence with higherpsychological data scores. Psychological data may thereforebe useful in determining when a player is at increased risk ofinjury.

REFERENCES

1. Borg, G. Borgs Perceived Exertion and Pain Scales. Champaign, IL:Human Kinetics, 1998.

2. Day, ML, McGuigan, MR, Brince, G, and Foster, C. Monitoringexercise intensity during resistance training using the session RPEscale. J Strength Cond Res18: 353358, 2004.

3. Dunbar, CC, Robertson, RJ, Baun, R, Blandin, MF, Metz, K,Burdett, R, and Goss, FL. The validity of regulating exercise intensity

by ratings of perceived exertion. Med Sci Sports Exer24: 9499, 1992.4. Dvorak, J, Junge, A, Chomiak, J, Graf-Baumann, T, Peterson, L,

Rosch, D, and Hodgson, R. Risk factor analysis for injuries in footballplayers: possibilities for a prevention program. Am J Sports Med28:6974, 2000.

5. Foster, C. Monitoring training in athletes with reference toovertraining syndrome. Med Sci Sports Exerc30: 11641168, 1998.

6. Foster, CL, Florhaug, JA, Franklin, J, Gottschall, L, Hrovatin, LA,Parker, S, Doleshal, P, and Dodge, C. A New approach to monitoringexercise training. J Strength Cond Res 15: 109115, 2001.

7. Gabbett, TJ. Severity and cost of injuries in amateur rugby league:A case study. J Sports Sci19: 341347, 2001.

8. Gabbett, TJ. Incidence of injury in semi-professional rugby leagueplayers. Br J Sports Med 37: 3645, 2003.

9. Gabbett, TJ. Influence of training and match intensity on injuries in

rugby league. J Sports Sci22: 409417, 2004.10. Gabbett, TJ. Reductions in pre-season training loads reduce training

injury rates in Rugby League players. Br J Sports Med 38: 743749,2004.

11. Gabbett, TJ and Domrow, N. Risk factors for injury in subelite rugbyleague players. Am J Sports Med 33: 428434, 2005.

12. Gabbett, TJ and Domrow, N. Relationships between training load,injury, and fitness in sub-elite collision sport athletes. J Sports Sci25: 15071519, 2007.

13. Gibbs, N. Injuries in professional rugby league: A three-yearprospective study of the South Sydney Professional Rugby LeagueFootball Club. Am J Sports Med 21: 696700, 1993.

14. Gissane, C, Jennings, DC, Cumine, AJ, Stephenson, SE, andWhite, JA. Differences in the incidence of injury betweenrugby league forwards and backs. Aust J Sci Med Sport29: 9194,

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analysis of injury incidence in rugby league football. Sports Med32: 211216, 2002.

16. Impellizzeri, FM, Rampinini, E, Coutts, AJ, Sassi, A, and Marcora, SM.Use of RPE-based training load in soccer. Med Sci Sports Exerc36: 10421047, 2004.

17. King, DA and Gabbett, TJ. Training injuries in New Zealand amateurrugby league players. J Sci Med Sport11: 565565, 2007.

18. King, DA, Gabbett, TJ, Gissane, C, and Hodgson, L. Epidemiologicalstudies of injuries in rugby league: Suggestions for definitions, datacollection and reporting methods. J Sci Med Sport12: 12-19, 2009.

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19. Lavallee, L and Flint, F. The relationship of stress, competitiveanxiety, mood state, and social support to athletic injury. J Athl Train31: 296299, 1996.

20. Meir, R, Arthur, D, and Forrest, M. Time and motion analysisof professional rugby league: A case study. Strength Cond Coach1: 2429, 1993.

21. Reynolds, KL, Harman, EA, Worsham, RE, Sykes, MB, Frykman, PN,

and Backus, VL. Injuries in women associated with a periodizedstrength training and running program. J Strength Cond Res15: 136143, 2001.

22. Seward, H, Orchard, J, and Hazard, H. Football injuriesin Australia at the elite level. Med J Aust159: 298306,1993.

23. Van Mechelen, W, Twisk, J, Molendijk, A, Blom, B, Snel, J,and Kemper, HC. Subject-related risk factors for sports injuries:A 1-yr prospective study in young adults. Med Sci Sports Exerc28: 11711179, 1996.

24. Wilson, BD, Quarrie, KL, Milburn, PD, and Chalmers, DJ. Thenature and circumstances of tackle injuries in Rugby Union.J Sci Med Sport2: 153162, 1999.



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