An examination of the training profiles and injuries in elite youth track and field athletes

This article was downloaded by: [RMIT University] On: 20 August 2014, At: 05:09 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK European Journal of Sport Science Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/tejs20 An examination of the training profiles and injuries in elite youth track and field athletes Dianne J. Huxleya, Donna O'Connora & Peter A. Healeyb a Faculty of Education and Social Work, University of Sydney, Sydney, NSW, Australia b Australian Sports Management Group, Sydney, NSW, Australia Published online: 19 Jun 2013. To cite this article: Dianne J. Huxley, Donna O'Connor & Peter A. Healey (2014) An examination of the training profiles and injuries in elite youth track and field athletes, European Journal of Sport Science, 14:2, 185-192, DOI: 10.1080/17461391.2013.809153 To link to this article: http://dx.doi.org/10.1080/17461391.2013.809153 PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. 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Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions http://www.tandfonline.com/loi/tejs20 http://www.tandfonline.com/action/showCitFormats?doi=10.1080/17461391.2013.809153 http://dx.doi.org/10.1080/17461391.2013.809153 http://www.tandfonline.com/page/terms-and-conditions http://www.tandfonline.com/page/terms-and-conditions ORIGINAL ARTICLE An examination of the training profiles and injuries in elite youth track and field athletes DIANNE J. HUXLEY1, DONNA O’CONNOR1, & PETER A. HEALEY2 1Faculty of Education and Social Work, University of Sydney, Sydney, NSW, Australia, 2Australian Sports Management Group, Sydney, NSW, Australia Abstract Australian track and field has a strong focus on State and National elite youth programmes as the development pathway to elite senior international competition. Yet, there are no clearly defined parameters for appropriate training volumes, training intensities or competition schedules for youth athletes. This study sought to examine the training profiles of, and injuries suffered by, elite youth track and field athletes between the ages 13 and 17 years. The participants were 103 elite NSW athletes (age 17.792.4 years, 64% girls) who recalled, through a questionnaire, their training profiles (frequency, volume and intensity) and injuries (type, site and severity) at three age groups: 13�14 years, 15�16 years and at 17 years of age. Eighty-one athletes (78.6%) sustained 200 injuries (time loss �3 weeks) that were predominantly classified as overuse (76%) with 17.3% of athletes retiring due to injuries prior to turning 18 years. The results, analysed using t-test, one-way analysis of variance and chi-square analysis, showed that injured athletes trained at a higher intensity at 13�14 years (p B0.01), completed more high-intensity training sessions at 13�14 years (p B0.01) and 15�16 years (p B0.05) and had a higher yearly training load at 13�14 years (p B0.01). There was a significant relationship between forced retirement and having sustained an overuse injury (pB0.05). These findings suggest that monitoring by coaches and athletes of training loads, intensity and the number of hard sessions completed each week is warranted to minimise injuries sustained by 13�16 year old athletes. Keywords: Athletics (or track and field), elite youth, training profile, injuries Introduction The sport of track and field in Australia has a strong focus on State and National elite youth programmes and a growing emphasis on global elite youth competition as the development pathway to elite senior international competition (Athletics Australia, 2011). However, there are no clearly defined parameters for appropriate volumes and intensities of training youth athletes (Mountjoy et al., 2008) or research into the long-term effects of rigorous training of, and competitive schedules for, these athletes (Capranica & Millard-Stafford, 2011). In addition, there is sparse research on injury rates, prevalence, type and severity affecting these athletes (Coulon, Lackey, Mok & Nile, 2001; Orava & Sareela, 1978; Requa & Garrick, 1981; Watson & Dimartino, 1987). Understanding the training and injury profiles of elite youth track and field athletes may assist in providing some guidance for a more effective athlete development programme and encourage further research in this area. With significant increases in personal rewards and national and international recognition for both athlete and coach, incentives to train harder are even greater today (Engebretsen et al., 2010). This can create an environment where young athletes specialise in one sport and train and compete at adult volumes and intensities all year-round subsequently increasing their risk of injury (Brenner, 2007; Difori, 2010) and in particular, overuse injuries traditionally seen in adults (Gerrard, 1993). Numer- ous studies involving a range of sports indicate training loads (Caine, DiFiori, & Maffulli, 2006), level of competition (Watson & DiMartino, 1987), Correspondence: D. J. Huxley, Faculty of Education and Social Work, Education Building A35, University of Sydney, NSW 2006, Australia. E-mail: [email protected] European Journal of Sport Science, 2014 Vol. 14, No. 2, 185�192, http://dx.doi.org/10.1080/17461391.2013.809153 # 2013 European College of Sport Science D ow nl oa de d by [ R M IT U ni ve rs ity ] at 0 5: 09 2 0 A ug us t 2 01 4 mailto:[email protected] http://dx.doi.org/10.1080/17461391.2013.809153 coach experience and coach education (Schulz et al., 2004), may be injury risk factors in youth athletes. It has been acknowledged that many elite youth track and field athletes in Australia do not transition into elite senior athletes (Bennie & O’Connor, 2006). This trend was also found in English athletes where only 7% of the top 20 U15 athletes (N�560) were ranked in the top 20 ten years later (Shibli & Barrett, 2011). While some attrition can be attrib- uted to competing interests such as work, study, family and other sports (Bennie & O’Connor, 2006), other studies have reported that inappropriate train- ing and competition loads at a young age has led to higher injury rates (Brenner, 2007; Difori, 2010) which contributed, in some cases, to premature retirement (Dixon & Fricker, 1993). A common reported reason for English athletes to drop out was the repeated injury and inability to recover to previous levels of attainment (Shibli & Barrett, 2011). The purpose of this study was to examine the training load (frequency, volume and intensity) and injuries (type, site and severity) sustained by elite youth athletes in New South Wales (NSW) when aged 13�17 years. Method Data were obtained from members of the New South Wales Institute of Sport Emerging Talent Squad (ETS) who participated in the programme between the years 2005 and 2010. Letters of invitation together with the self-reporting paper-based ques- tionnaire and participant information was distribu- ted by postal mail to the last known address of all athletes over 18 years and to the parents of athletes under 18 age years (N�476). Parents of athletes under 18 were requested to assist their daughter/son complete the questionnaire in an effort to reduce the recall bias normally associated with children and adolescents (Soberlak & Cote, 2003). The study was approved by the University of Sydney Human Research Ethics Committee and the New South Wales Institute of Sport. Development of the questionnaire was based on protocols used in previous studies (Helsen, Starkes, & Hodges, 1998; Memmert, Baker, & Bertsch, 2010) that retrospectively collected data using a one-week training diary for various age groups. A reasonable level of accuracy (r�0.73) has been reported for athletes recalling their practice history (Baker, Cote, & Abernethy, 2003; Memmert et al., 2010). Face and content validity of the questionnaire were assessed using a pilot test with 10 similar-aged athletes and seeking advice and feedback from experts in both youth sport and education. Subsequent modifications were made based on athlete feedback and experts’ recommendations. The questionnaire gathered information regarding the athletes’ participation in track and field between the ages of 13 and 17 years and covered athlete demographics, training specifics (frequency, inten- sity, hours and modality), frequency and nature of injuries. Data were collected in relation to three different age groups: 13�14 years, 15�16 years and at 17 years of age. For the purpose of this study, an injury was defined as one resulting in the athlete missing more than three weeks of athletics’ training or competi- tion. To analyse the perceived intensity of training, athletes were asked to rate the intensity of each training session for one ‘average’ week at each of the three age groups using a simple scale; easy �1, medium difficulty �2, hard �3 and very hard �4. To calculate the weekly intensity of an athlete’s training, the number of sessions of each rating was multiplied by the assigned number (1�4), the sum of which gave an overall weekly intensity measure [e.g. (1�2)�(2�3)�(1�4) �12 (weekly inten- sity)]. To be able to investigate more thoroughly the link between intensity and injury in youth athletes a further measure of intensity (high inten- sity) was also calculated by using the same method for the hard and very hard sessions [e.g. 2�3� 1�4 �10 (weekly high intensity)]. To investigate links between training volumes (hours), intensity and injury incidence, annual training load was calculated by multiplying the number of weeks of training in a year by the weekly training intensity. A cumulative training load for each athlete was also calculated by adding together the total annual training load at each age group. Means9standard deviations (sd) and percentages were calculated for all variables (SPSS version 18). Differences between injured and uninjured athletes as well as gender effects were analysed using a t-test. One-way analysis of variance was used to compare training and injury profiles among age groups and discipline groups. Chi-square analysis was employed to compare the observed and expected ‘counts’ of categorical variables. The significance level set at p B0.05 was used for determining statistical signifi- cance between the groups. Results One hundred and three athletes (17.792.4 years; 34 males, 66 females, 3 unidentified) completed the questionnaire with the majority (70.6%) being members of the 2009 and 2010 ETS. A large percentage (94.2%) of athletes had participated in Little Athletics (LA) with 77.7% for five years or more. The mean start age of athletes in LA was 186 D. J. Huxley et al. D ow nl oa de d by [ R M IT U ni ve rs ity ] at 0 5: 09 2 0 A ug us t 2 01 4 7.692.3 years with an average participation of 6.992.3 years. Participants specialised in the follow- ing events: distance run/walk (32), sprints/hurdles (24), multievents (20), jumps (15) and throws (12). All athletes had competed to at least national level with 44% competing at international level. A large percentage of the athletes’ coaches (76%) were qualified through the Australian Track and Field Coach Association (ATFCA) and held either, a level 4/5 (51%) or level 1�3 (25.3%) qualification. Table I provides an overview of the training profile of athletes during the ages of 13�17 years. There was a significant increase in the number of training sessions completed (pB0.01) and the num- ber of hours spent training each week (pB0.001) as an athlete moved through the three age groups. When comparing the training profiles of athletes at the various age groups significant increases were recorded in terms of weekly intensity and high- intensity training sessions, and annually with respect to training hours and the amount of high-intensity training completed. Thirteen- to fourteen-year-old athletes on average rated at least one session per week very hard with 53.8% of training sessions rated as ‘hard’ or ‘very hard’ annually. More than half (64.7%) were training between 10 and 12 months of the year. By 15�16 years 63.5% of training sessions were deemed ‘hard’ or ‘very hard’ and the majority of athletes (76%) trained between 10 and 12 months of the year. At 17 years 2�3 sessions (out of 5) were rated as ‘hard’ or ‘very hard’ with 74.2% training between 10 and 12 months of the year and 25.8% all year. There was no significant difference between gender and any aspect of the training profile. Eighty-one athletes (78.6%) sustained 200 injuries with 74% of these athletes injured more than once and 14.6% requiring surgery. The majority (92%) of athletes recalled receiving sports medicine treatment for their injury. The most common injury site was ankle or foot (56.8%) followed by lower leg (34.6%), upper leg (32.1%), core injuries (27.2%), knee (23.5%) and upper body (17.3%). There was no significant difference between gender and injury site. The most frequent type of injury sustained was muscle strains (38.8%), followed by bone stress injuries (33%), tendinopathy (27.2%), ligament sprains (10.7%), fractures (8.7%), shin pain (8.7%), avulsions (4.9%) and dislocations (2.9%) with overuse injuries (i.e., tendonitis, bone stress injuries) sustained by 60.2% of the athletes. There was no significant difference between the incidences of injury sustained by athletes from the various event disciplines. There was no significant relationship between gender and sustaining an in- jury. However, there was a trend for females to be more likely to sustain an overuse injury (p�0.058). Table II compares the training profiles of injured and uninjured athletes. Analysis revealed that injured athletes trained at a significantly higher weekly intensity and completed a significantly higher yearly training load at 13�14 years compared to uninjured athletes. In addition injured athletes subjectively recalled that training was ‘harder’ each week than uninjured athletes at 13�14 years and at 15�16 years for more months of the year. Table II also compares the training profiles of athletes that sustained an overuse injury and those that did not. There was no significant difference in the number of training sessions between injured (overuse) and uninjured (overuse) athletes. How- ever, athletes that sustained an overuse injury self- reported they had a significantly higher weekly and yearly training load during the ages of 13�16 years. During this age span athletes sustaining an overuse injury also reported training significantly ‘harder’ (pB0.01). There was no significant difference in any aspect of training profiles between injured and uninjured athletes at the age of 17 years. Table I. Training profile of athletes during age groups 13�14 years 15�16 years 17 years Training profile N Mean9sd N Mean9sd N Mean9sd Sessions/week* 100 3.3691.28 97 4.3791.70 66 5.0692.20 Weekly training hours** 100 5.6992.53 97 7.3093.30 66 8.9293.69 Weekly intensitya** 100 7.7893.23 96 10.5294.08 65 13.3795.72 Weekly high intensityb** 100 4.0193.73 96 6.5494.64 65 9.7196.05 Annual training hours 100 244.119128.88 93 334.709154.51 63 409.849181.99 Annual training loadc** 100 336.579170.62 97 468.049227.20 64 604.869311.62 Annual high intensity** 100 180.999175.68 97 297.399223.04 64 447.369295.07 aThe self-reported level of the perceived intensity of each training session using the scale; easy �1, medium difficulty �2, hard �3 and very hard �4, multiplied by the number of those training sessions completed in a week. bThe hard and very hard sessions using the perceived intensity of training scale multiplied by the number of those training sessions completed in a week. cThe number of weeks of training in a year multiplied by the weekly intensity. *p B0.01 between each group; **p B0.001 between each group. Training profiles of elite youth track and field athletes 187 D ow nl oa de d by [ R M IT U ni ve rs ity ] at 0 5: 09 2 0 A ug us t 2 01 4 Fourteen athletes (17.3% of injured athletes) reported that they were forced to retire due to injury. Chi-square analysis revealed a significant relationship between forced retirement and having sustained an overuse injury [x2 (1, N�81) �5.72, p�.017]. Further analysis indicated that bone stress injuries were associated with forced retirement [x2 (1, N� 81) �6.28, p�0.012]. Athletes who were forced to retire trained at a significantly higher weekly intensity (rating of 1093.2 vs. 7.893.0, pB0.05) and trained ‘harder’ (6.594.6 vs. 4.193.4, pB0.05) at the age of 13�14 years. They completed a significantly higher yearly training load at 13�14 years (444.09214.0 vs. 345.99155.6, pB0.05) and trained at a significantly higher intensity throughout the year (299.19157.8 vs. 184.89157.8, pB0.05). Figure 1 highlights the relationship between weekly training intensity, injury and forced retirement. Athletes forced to retire had more injuries (3.0 vs. 2.53, pB0.05) and signifi- cantly longer time off (weeks) as a result of an injury (30.3927.7 vs. 11.9910.1, pB0.01) suggesting their injuries were significantly greater than other injured athletes. There were no other significant factors across the training profiles of the athletes. Surgery was not a significant factor in relation to forced retirement due to injury (p�0.05). Table II. A comparison of training profiles of injured and uninjured athletes and overuse injuries Age in years No injury Injured No overuse injury Overuse injury Means9sd Means9sd p-Value Means9sd Means9sd p-Value 13�14 no. sessions/week 3.0591.46 3.4591.22 0.194 3.2091.29 3.4791.28 0.286 13�14 weekly intensity 6.2393.27 8.2293.11 0.010** 6.6392.71 8.5893.35 0.003** 13�14 weekly high intensity 2.1893.14 4.5393.73 0.008** 2.3992.91 5.1493.84 0.000*** 13�14 annual high intensity 95.659144.64 205.069176.94 0.009** 105.299135.41 233.609182.13 0.000*** 13�14 annual training load 240.719143.34 363.619168.70 0.002** 272.059138.72 381.419177.29 0.001*** 13�14 annual training hours 213.329182.65 252.799109.13 0.343 221.689144.34 259.699115.66 0.148 15�16 no. sessions/week 4.5791.89 4.3291.66 0.546 4.3791.81 4.3891.64 0.979 15�16 weekly intensity 9.6793.51 10.7694.21 0.280 9.1793.21 11.5394.38 0.003** 15�16 weekly high intensity 4.7194.33 7.0594.62 0.040* 4.1794.01 7.9194.63 0.001*** 15�16 annual high intensity 95.659144.65 205.069176.94 0.009** 212.289178.02 359.709233.31 0.001*** 15�16 annual training load 411.149198.82 483.769233.19 0.196 401.119172.02 634.729290.80 0.008** 15�16 annual training hours 303.009169.74 343.949149.79 0.288 300.059138.90 362.029161.89 0.054 17 no. sessions/week 4.9192.05 5.6992.75 0.252 4.7392.59 5.2891.92 0.331 17 weekly intensity 14.5497.43 13.0895.26 0.415 12.2396.80 14.1394.83 0.193 17 weekly high intensity 10.6297.26 9.4895.76 0.549 8.5496.64 10.4995.57 0.205 17 annual high intensity 496.929344.53 434.739283.58 0.502 408.689317.32 472.159281.32 0.405 17 annual training load 635.629393.40 597.029291.38 0.693 558.289342.51 634.729290.80 0.342 17 annual training hours 410.009213.24 409.809175.42 0.997 378.329169.37 430.589189.15 0.268 13�17 annual high intensity 217.189146.34 294.939177.17 0.062 207.199137.07 329.309179.59 0.000*** 13�17 annual training load 386.689179.04 460.689183.24 0.095 383.569152.76 488.829192.95 0.004** 13�17 total high intensity 591.919450.85 772.309543.07 0.156 540.339395.82 872.409568.72 0.001*** 13�17 total training load 1008.79599.28 1180.09607.67 0.243 966.429499.55 1270.29648.29 0.008** 13�17 average hours 281.329153.51 310.449126.01 0.362 277.889121.14 323.109137.30 0.087 13�17 total training hours 744.689458.92 807.579415.06 0.539 717.219389.02 849.279441.11 0.119 *p B0.05; **p B0.01; ***p50.001. 0 2 4 6 8 10 12 14 13–14 years 15–16 years 13–14 years 15–16 years Athletes by age group No injury Injury Overuse Stress fracture Forced retirement L ev el o f w ee kl y tr ai ni ng in te ns it y Weekly training intensity 0 1 2 3 4 5 6 7 8 9 10 Athletes by age group No injury Injury Overuse Stress fracture Forced retirement * * ** ** *** ** ** * ** ** ** ** L ev el o f w ee kl y hi gh –i nt en si ty t ra in in g Weekly high intensity training Figure 1. The threshold effect of training intensity and high intensity. The graphs illustrate the relationship between weekly intense training and weekly high intense training to injury, overuse injury, stress fracture and forced retirement for the younger age groups. *p B0.05; **p B0.01. 188 D. J. Huxley et al. D ow nl oa de d by [ R M IT U ni ve rs ity ] at 0 5: 09 2 0 A ug us t 2 01 4 Discussion Although the results indicate that the training frequencies of athletes in this study exceeded the recommended guidelines of the ATFCA model (Australian Track and Field Coaches Association [ATFCA], n.d.) for youth athlete development in both frequency (13�15 years, 2 sessions/week) and average weekly training hours for 13�14 years (5.69 hours vs. 3.0 hours), the findings were similar to other youth athletics studies (Henriksen, Stambulova, & Roessler, 2010; Orava & Saarela, 1978; Watson & DiMartino, 1987). However, the athletes’ mean weekly training hours were significantly lower than the training hours of elite youth athletes in gymnastics, tennis and swimming (Maffulli, King, & Helms, 1994). Although it is difficult to make comparisons with other sports given the variation in sport-specific training modalities, the total training time was not a significant factor in injury prevalence, a finding supported by other track and field studies (Bennell & Crossley, 1996; Watson & DiMartino, 1987). The significant increase in training intensity does not align with training practices of youth athletes as reported by several studies ( Henriksen et al., 2010; MacPhail & Kirk, 2006) emphasising general development, variety and the correct technique up to the age of 15�16 years. A number of possible explanations for the intense level of training of these young athletes may include participation in LA at a young age, unrealistic com- petition structures, Australian performance standards more difficult to achieve than the international standards and coaches’ lack of knowledge regarding youth athletes. LA is based on the adult competition model typically incorporating event specific training. Given the early commencement age in track and field of the study cohort, it appears likely that many of the athletes had acquired several years of athletic training before they reached 13 years. If this is the case, high-intensity training at 13�14 years may be accepted as the norm by the athletes, parents and coaches. This may reflect the ‘catch them when young’ philosophy of some coaches who prescribe intensive training before adolescence in order to achieve success (Baxter-Jones & Mundt, 2007). Three separate competition pathways for youth athletes in NSW are organised throughout the year by sporting bodies independent of each other result- ing in a year-round competition schedule. This may partly explain why athletes reported high levels of ‘harder’ training all year. It has been recommended that young athletes take 2�3 months off from specific sport training and competition each year (Brenner, 2007) to ensure there are opportunities for complete recovery. Between the ages of 15 and 17 years, a major focus of elite youth squads is representing Australia at four international competitions (Athletics Austra- lia, 2011). The International Association of Athletics Federations (IAAF) generally sets the entry stan- dards for these competitions; however, Australian entry standards are more difficult and may necessi- tate higher intensity and training loads for athletes to achieve these standards. Coaches may lack specific knowledge and exper- tise in coaching young athletes (MacPhail & Kirk, 2006; Shibli & Barrett, 2011) as much of the coach education curriculum in Australia focuses on adult training methods (Australian Track and Field Coaches Association [ATFCA], 2011a). This is supported by the ATFCA database which lists only 4.8% of coaches in NSW as having completed the level 4 option ‘coaching the young athlete’ (Australian Track and Field Coaches Association [ATFCA], 2011b), a course designed to coach 10� 15 year old athletes (Australian Track and Field Coaches Association [ATFCA], 2011a). The results of this study showed that between the ages of 13 and 17 years the risk of injury to youth track and field athletes was high. Although previous youth track and field studies report significant variations in the number of athletes that sustain an injury (Coulon et al., 2001; Orava & Saarela, 1978; Watson & DiMartino, 1987), it is difficult to make comparisons due to different injury definitions, length of observation period and standard of athletes. The athletes’ elite status may be a factor in the high number of injuries sustained as injury incidence has been linked to higher competition level in youth athletes (Maffulli et al., 1994). With the competition demands and expectations of the athletes in this study, one possible explanation for the occurrence of multiple injuries maybe premature return to sport before full rehabilitation (Orchard, 2001). Consistent with other track and field studies (Alonso et al., 2009; Bennell & Crossley, 1996; D’Souza, 1994; Watson & DiMartino, 1987), the majority of injuries occurred in the lower body, in particular the foot and ankle. The most common injuries included those involving muscle and tendon damage and overuse injuries, again consistent with the findings of other track and field studies in both youth (Requa & Garrick, 1981; Watson & DiMartino, 1987) and senior athletes (Alonso et al., 2010; Bennell & Crossley, 1996). As with several other studies in track and field (Bennell & Crossley, 1996; Coulon et al., 2001; Requa & Garrick, 1981), gender was not a signifi- cant factor in injury occurrence, although in this study there was a trend for females to sustain more overuse injuries. The results indicate a significant association between high-intensity training and high annual Training profiles of elite youth track and field athletes 189 D ow nl oa de d by [ R M IT U ni ve rs ity ] at 0 5: 09 2 0 A ug us t 2 01 4 training load at 13�16 years and high-intensity training at 15�16 years and injury, in particular overuse injuries. This is consistent with findings of previous studies that have associated overuse injuries with excessive training loads, increases in intensity and competition over scheduling (Brenner, 2007; Gerrard, 1993; Orava & Saarela, 1978). The incidence of stress fractures, higher than some other studies involving senior athletes, (Bennell & Crossley, 1996) together with the long periods of training and competition time lost due to injury may also indicate overtraining. The high percentage of athletes sus- taining an overuse injury (60.2%) is a major concern as analysis revealed a significant relationship between forced retirement and having sustained an overuse injury a finding supporting that of Ristolainen, Kettunen, Kujala, and Heinonen (2012). In this study, 17.3% of the injured athletes were forced to retire due to injury compared with 8% of Australian Gymnasts (aged 9�19 years; similar sample size) studied over a 10-year period (Dixon & Fricker, 1993). Track and field is regarded as a late specialisation sport (Balyi, 2001) with athletes peak- ing in mid- to late twenties (Shibli & Barrett, 2011), whereas gymnastics is an early specialisation sport with a large amount of deliberate practice from an early age (Balyi, 2001). Based on this comparison, it may be speculated that early specialisation in LA from a young age together with intense training between 13 and 16 years are compounding factors in premature retirement due to injury. As shown in Figure 1, there are thresholds in the amount of intense training younger athletes were able to cope with. Exceeding these thresholds either through intense or high-intensity training signifi- cantly increased the risk of injury, and in particular stress fractures. Loud, Gordon, Micheli, and Field (2005) similarly reported a threshold or ‘break point’ in relation to stress fractures in preadolescent and adolescent girls involved in high impact activities such as running. Interestingly, the training profile in relation to injury occurrence at 17 years was not a significant factor. One possible explanation for this may be Darwin’s ‘survival of the fittest’ principle with the ‘survivors’ by age 17 genetically predisposed to successfully adapting to the greater training loads during growth and maturation (Capranica & Millard- Stafford, 2011). However, as 36% of the athletes surveyed did not complete details as a 17-year-old athlete (either they were under 17 years of age or retired before they reached 17), the sample size may have been too small to reveal significant differences. Limitations As for all studies of this type it is limited by the reliance on a self-reported retrospective recall of the athlete’s training and injury history. In an attempt to minimise recall bias associated with training history, athletes were questioned on specific habitual experi- ences as previous research has indicated a better recall of this type of information (Leite, 2009) with reliable recall being demonstrated in younger elite athletes for periods of 20�25 years (Baker et al., 2003). It was hypothesised that because training activities play such an important part in athletes’ lives recall of such activities may be more accurate (Moesch, Elbe, Hauge, & Wikman, 2011). The study is also limited by utilising a subjective rating of training intensity; however, given that children younger than 10 years are able to accurately rate their perceived effort (Eston, Lamb, Bain, Williams, & Williams, 1994), it is postulated that older athletes’ perceived rating of effort should be reason- ably accurate. A prospective longitudinal study using a weekly training diary is needed to address these limitations to confirm the findings of this study. Finally, we utilised a time loss injury definition (�3 weeks) which provides a conservative profile of injuries sustained. This definition was used as previous studies (Askling, Lund, Saartok, & Thorstensson, 2002; Ristolainen et al., 2012) sug- gest injury recall bias is mitigated in relation to serious injuries that had longer symptoms and affected performance and training or required con- sultation by a physician (Twellaar, Verstappen & Huson, 1996). Given the limitations outlined caution must be exercised in generalising these findings to other track and field populations. While training intensity was linked to increased injury occurrence it is only one of many factors (psychological, behavioural and environmental) that need to be considered in understanding injury in youth athletes. Practical applications This study has several practical applications for the training, coaching and competition structure for elite youth track and field athletes. The high incidence of overuse injuries and its link to early retirement reflect a need for specific education programmes targeting those working directly with youth track and field athletes. Injury in youth athletes has been attributed to intense and long competition calendars and research suggests that the focus in the adolescent years should be on development rather than results and competition. The outcome of the study may raise awareness within the governing bodies of the sport of the possible injury risks associated with the current competition structure in Australia for youth track and field athletes and in turn open up the exploration of alternate pathways. As exceeding a training intensity ‘threshold’ led to increased injury 190 D. J. Huxley et al. D ow nl oa de d by [ R M IT U ni ve rs ity ] at 0 5: 09 2 0 A ug us t 2 01 4 risk in youth athletes, a simple method in which athletes rate perceived intensity could be adopted and implemented to monitor and keep training intensity below the threshold. Conclusion Training intensity and load at 13�14 years and high- intensity training at 15�16 years are associated with sustaining an injury as a 13�17 year old athlete. Injury severity led to significant time loss from training and competition and in 17.3% of cases to forced retirement. Training intensely at 13�16 years resulted in a high percentage of overuse injuries but total training time was not a factor in injury implying the type, not training duration is the contributing factor to injury. 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