Undertraining: A Likely Cause for the Rise in Youth Sport Injuries

Published On: mars 29, 2021Categories: Formation des jeunes

Injuries are on the rise in youth sports.

A study published in the American College of Sports Medicine (Faigenbaum, 2009) has shown that in the United States, between 15-28% of youth baseball, basketball, soccer and football players are injured each year, resulting in games missed. The same study found that, in New York State alone, the number of anterior cruciate ligament (ACL) reconstructions performed on children aged 3-20 has increased by 100% from 1990 to 2009, and since the year 2000, there has been a five-fold increase in upper body injuries in youth baseball and softball players.

Overuse injuries – differentiated from acute injuries in that they involve repetitive strain placed on bones, tendons, and ligaments, as opposed to an acute traumatic event – are also a notable problem in youth sports. Youth athletes between the ages of 8-14 are more susceptible to overuse injuries than adult athletes, because they have growth cartilage in specific anatomical sites in the body. Since growth cartilage is considered « prebone, » it is more vulnerable to damage from repetitive microtrauma than fully formed bone, and early damage to it can even lead to permanent injury and disability later in life (Micheli, 2006).

A position statement from the American Medical Society for Sports Medicine, DiFlori et al. (2014) noted that estimates of overuse injuries versus acute injuries range from 45.9% to 54%, and that an underestimation of overuse injuries exists in the literature since most studies about injuries use the criteria of requiring a time loss from participation.

Among the reasons cited by medical experts for this rise in both acute and chronic injuries in youth sports are that children are “overtraining”; playing too many sports in general, and/or playing one sport too often (DiFlori et al., 2014, Carder et al., 2020). For example, many youth sports programs today, including soccer programs, require a commitment of several days per week from children beginning as young as age 6 or 7. By the age of 13, the highest competitive levels in youth soccer train year-round, with 3-4 training sessions plus at least one game per week throughout the year (Faigenbaum, 2009).

This type of early sport specialization is certainly a problem for young athletes, as recent research has demonstrated a direct link between year-round participation in only one sport, and higher incidence of injuries, as compared to participation in multiple sports (Field et al., 2019).

Interestingly, though, over the past 20 years – during the exact same time period – overall rates of inactivity and obesity in children have also significantly increased (De Onis et al., 2010).

Today children are far less active, and far more overweight than they used to be, yet at the same time, they are specializing in one sport much earlier, and playing much more of their specialized sport, than they ever did before.

In response to growing concerns over increased injury rates in North American youth sports, many sports organizations – including soccer governing bodies, like Ontario Soccer in their Ontario Player Development League – have placed restrictions on the amount of soccer activity, and overall physical activity, that youth athletes can participate in.

So essentially, the “solution” proposed for youth athletes who are experiencing increased injury rates, is to have them play less sports, in order to reduce the risk of injury.

While early sport specialization is undoubtedly a problem, it might be possible that young athletes aren’t “overtraining” at all; and in fact, my hypothesis is that youth athletes may actually be “undertraining”. As a result of this, it has led them to become out of shape and unprepared for the demands of the sport they are participating in, leading to increased rates of injury.

Although the conventional approach of having sports governing bodies reduce physical activity levels in youth athletes may seem intuitive, it ignores one of the root causes of injury in youth sports – or any sports for that matter – which is, unpreparedness for the physical demands of the sport itself.


Although overtraining is real, it just isn’t very likely that the youth athletes constantly getting injured in North America are actually overtraining.

In a Consensus Statement published by the European College of Sports Science (ECSS), Meussen et al. (2013) recently identified three separate “stages” or phases of overtraining syndrome, with progressively worsening symptoms:

  1. Functional over-reaching: increased short-term (1-2 weeks) training load, with short-term performance decrements, but long-term adaptation due to supercompensation (or, improvement of fitness and work capacity).
  2. Non-functional over-reaching: intense training leading to long-term (weeks to months) performance decrements, but with a full recovery after rest.
  3. Overtraining syndrome: Consistent with non-functional over-reaching but with longer-term (greater than 2 months) performance decrements, and more severe symptoms.

As the third and most severe stage, true overtraining syndrome involves sustained, high-volume, high-intensity training, on most days of the week, leading to maladaptive responses in the physiological, neurological, endocrine, and immune systems, and a potential long-term or even permanent stop of an individual’s athletic career (Kreher & Schwartz, 2012).

Among the physical and physiological signs and symptoms of overtraining syndrome (Kreher & Schwartz, 2012) include:

  • Parasympathetic alterations: fatigue, depression, bradycardia (chronically low heart rate), and loss of motivation
  • Sympathetic alterations: Insomnia (trouble falling and/or staying asleep), irritability, agitation, tachycardia (chronically high heart rate), hypertension, restlessness
  • Others symptoms: Anorexia, weight loss, lack of mental concentration, heavy, sore and stiff muscles, anxiety

Typically, overtraining syndrome affects athletes at the highest levels, as these are the only ones who are fit enough to sustain this type of abnormally high workload long enough to experience the symptoms; most other athletes would simply not be able to keep up after only a few days or workouts.

In fact, Budgett (1998) noted that functional over-reaching is the first recognized “stage” of overtraining syndrome, and functional over-reaching involves positive improvements and adaptations to the aerobic system. Thus, it is likely not possible for athletes to get to the later stages of overtraining syndrome without first having achieved significant improvements in their aerobic fitness.

Consequently, while overtraining is certainly a problem that sport and performance coaches need to contend with, it is very likely completely unrelated to the rise in youth sports injuries discussed in this article, because the great majority of North American youth athletes are not aerobically fit enough to handle the sustained high workloads associated with overtraining syndrome (Gabbett, 2016).

Instead, it is far more likely that the lack of aerobic fitness and physical resiliency, due to underpreparation for the practice and game loads, which in turn leads to long-term over-reaching and lack of proper recovery, are to blame (Faigenbaum, 2009). While it may be impossible to know exactly how much aerobic fitness and overall conditioning is required to allow youth athletes to tolerate the high training loads required to build and improve fitness without risk of overtraining, many sports medicine experts believe that both acute and chronic youth sports injuries can be reduced by 15% to 50% with adequate attention placed on aerobic conditioning (Micheli, 2006).


My views on this have been informed by conducting fitness assessments of athletes across Canada for the past 15 years. From the results of my assessments, Canadian youth soccer players are not in comparable shape to youth in other nations.

On average, the fitness level of a “competitive” rep or academy soccer player in Canada is nowhere near the standards of professional high-performance youth soccer environments in other countries.

To give just one example, in a recent study I conducted and presented at the 5th World Conference on Science and Soccer in Rennes, France (2017) I compared the fitness test scores between members of the Toronto FC Academy (a top Canadian youth soccer team) and other, lower-level Canadian youth soccer teams, with those of the Academy of Canadian SC Uruguay (a professional soccer club in the Segunda Division or 2nd Division). In this analysis, I found that boys in the U14-U16 age categories had scores on the Yo-Yo Intermittent Recovery Test – widely considered the best measure of a soccer player’s fitness – that were equal to those of the top Canadian youth soccer academy, and were also between 20-30% higher than the average Canadian rep teams I had tested in the same age categories (Bucciarelli & Yousefian, 2017).

Despite the fact that our youth players are not in comparable shape, we expect them to compete – that is, to play in regular weekly competitions – with the same volume, frequency, and intensity as their professional youth counterparts, who are in much better physical condition and therefore are much better prepared for these demands.

Could it be that in Canada, youth athletes are in fact “undertrained” – unprepared for the physical and physiological demands of sport competition – and that this unpreparedness could be contributing to the higher injury rates we see in Canada? Although there is no research comparing injury rates between countries, I feel this is a major factor.

Think about it this way: in any sports team (youth or adult), at any competitive level (grassroots to professional), the athletes who get injured less frequently and return to activity fastest from the injuries they do incur, are the ones who are the most aerobically fit. This is because injury risk is negatively correlated to aerobic fitness, while the ability to recover from injury is strongly correlated to it (Gabbett, 2016).

Simply put, fit players get hurt less, and recover faster from injuries, than unfit players (Asharnehzad et al., 2011, Tomlin & Wenger, 2001, Helgerud et al., 2001).

Many recent studies support these facts, including, specifically, that athletes with higher levels of aerobic fitness:

  • Have a significantly lower risk of injury (Afsharnehzad et. al., 2011)
  • Recover better in between bouts of high-intensity exercise (Tomlin & Wenger, 2001)
  • Perform better physically during periods of multiple high-intensity competitions (Helgerud et. al., 2001)

Thus, if youth athletes can raise their aerobic fitness levels, they will be better prepared for the demands of sports competition, including soccer competition. As a result, they may get injured less frequently, and are likely to recover quicker from any injury they incur compared to those who are less fit.


What is the best way for youth athletes to improve their aerobic fitness?

Through gradual, incremental increases in training load, which apply just enough stress to athletes’ physical and physiological systems to stimulate them to adapt and improve, but not so much that they overload the systems and cause them to break down.

In fact, several recent studies have determined that the main cause of injuries among both youth and adult athletes is a preceding spike in training load (Jones et al., 2016). If coaches and fitness coaches learn how to better plan and monitor training load, they can work to avoid these large spikes from one week to the next, significantly reducing injury risk in the process.

To assist coaches with their fitness plans, I have recently published articles, Video Blogs, and conducted a 1-hour Webinar that discuss how to calculate training load, plan optimal training load, and monitor the results of training, in order to achieve the gradual incremental increases needed to produce results and reduce injury risk. Links to these articles are included below.

I would also recommend reading Gabbett (2016), and subsequent follow-up studies by Myers et al. (2020), Sedaud et al. (2020), and Tiernan et al. (2020) where the ratio between acute (short-term) and chronic (long-term) training load has been described as a critical variable for injury prevention in athletes.

With a sound foundational understanding of the principles of periodization of training load, and how to monitor both acute and chronic workload, coaches and athletes can better prepare themselves for the demands of training and competition. This will combat and eliminate undertraining, so athletes will experience fewer injuries and recover faster when they do.

Soccer Fitness Goals Video Blogs: The key to better Fitness Training
Part 1: Do It Right: Measure, Monitor & Prescribe Training Load ACCURATELY, without Technology (Pt. 1)

Part 2: Measure, Monitor & Prescribe Training Load ACCURATELY, without Technology & Improve Recovery (Pt. 2)

Part 3: How To Calculate Training Load from Volume and Intensity Data – Excel Tutorial (Part 3)

Article: Load Management – The Key to better Fitness Training


Afsharnezhad, T., Sefatian, A., Burbur, A. (2011). The relationship among flexibility, aerobic fitness, leg extension power and agility with lower extremity injuries in footballers. International Journal of Sports Science and Engineering, 5(2): 105-111.

Faigenbaum, A.D. (2009). Overtraining in youth athletes: How much is too much?, ACSM’s Health & Fitness Journal, 13 (4): 8-13

Buccairelli, R. & Yousefian, F. (2017).  A comparison of speed and high intensity running ability between Canadian and Uruguayan professional academy soccer players.  [Conference presentation abstract]. 5th World Conference on Science and Soccer, Rennes, France, 2017.  https://www.soccerfitness.ca/wp-content/uploads/2010/05/A-comparison-of-speed-and-high-intensity-running-ability-between-Canadian-and-Uruguayan-professional-academy-soccer-players.pdf

Budgett, R. (1998). Fatigue and underperformance in athletes: the overtraining syndrome. British Journal of Sports Medicine, 32:107-110.

Carder, S.L., Giusti, N.E., Vopat, L.M., Tarakemeh, A., Baker, J., Vopat, B.G., Mulcahey, M.K (2020). The concept of sport sampling versus sport specialization: preventing youth athlete injury – a systematic review and meta-analysis. The American Journal of Sports Medicine; 48(11):2850–2857.

De Onis, M., Blössner, M., Borghi, E. (2010). Global prevalence and trends of overweight and obesity among preschool children, The American Journal of Clinical Nutrition, 92 (5): 1257–1264.

DiFiori JP, Benjamin HJ, Brenner JS, et al Overuse injuries and burnout in youth sports: a position statement from the American Medical Society for Sports Medicine. British Journal of Sports Medicine 2014;48:287-288.

Field, A. E., Tepolt, F. A., Yang, D. S., & Kocher, M. S. (2019). Injury risk associated with sports specialization and activity volume in youth. Orthopaedic Journal of Sports Medicine. 7(9): https://doi.org/10.1177/2325967119870124

Gabbett, T.J. (2016). The training—injury prevention paradox: should athletes be training smarter and harder? British Journal of Sports Medicine, 50:273-280.

Helgerud, J., Engen, L.C., Wisloff, U., Hoff, J. (2001). Aerobic endurance training improves soccer performance. Medicine and Science in Sports and Exercise, 12: 1925-1931.

Jones, C. M., Griffiths, P. C., & Mellalieu, S. D. (2017). Training load and fatigue marker associations with injury and illlness: A systematic review of longitudinal studies. Sports Medicine (Auckland, N.Z.), 47(5), 943–974.

Kreher, J.B. & Schwartz, J.B. (2012). Overtraining syndrome: a practical guide. Sports Health, 4(2):128-138.

Meeusen, R., Duclos, M., Foster, C., Fry, A., Gleeson, M., Nieman, D., Raglin, J., Rietjens, G., Steinacker, J., Urhausen, A. (2013). Prevention, diagnosis and treatment of the overtraining syndrome: Joint consensus statement of the European College of Sport Science (ECSS) and the American College of Sports Medicine (ACSM). European Journal of Sport Science. 13. 10.1080.

Micheli L. (2006). Preventing injuries in sports: What the team physician needs to know. In: Chan, K., Micheli, L., Smith, A., Rolf, C., Bachl, N., Frontera, W., Alenabi, T. F.I.M.S. Team Physician Manual. 2nd ed. Hong Kong, China: CD Concept: 555-72.

Myers, N. L., Mexicano, G., & Aguilar, K. V. (2020). The association between noncontact injuries and the acute—chronic workload ratio in elite-level athletes: A critically appraised topic, Journal of Sport Rehabilitation, 29(1), 127-130.

Sedeaud, A., De Larochelambert, Q., Moussa, I., Brasse, D., Berrou, J. M., Duncombe, S., Antero, J., Orhant, E., Carling, C., & Toussaint, J. F. (2020). Does an optimal relationship between injury risk and workload represented by the « Sweet Spot » really exist? An example from elite French soccer players and pentathletes. Frontiers in Physiology, 11, 1034.

Tiernan, C., Comyns, T., Lyons, M., Nevill, A. M., & Warrington, G. (2020). The association between training load indices and injuries in elite soccer players. Journal of Strength and Conditioning Research, 10.1519

Tomlin, D.L., & Wenger, H.A. (2001). The relationship between aerobic fitness and recovery from high intensity intermittent exercise. Sports Medicine, 31 (1): 1-11.

Author Biography

Richard Bucciarelli, MS, B.Kin., R.Kin, CSCS, CSEP-CEP, USSF “A”, is a professional fitness coach, sports scientist and coach educator, and the owner of Speed Training, a sport-specific strength and conditioning company in Toronto.

Richard has worked at some of the highest levels in the sport of soccer, both in Canada and internationally, including the Canadian National Women’s Soccer Teams, the Toronto FC Academy, The Uruguayan Segunda (second division) with Canadian SC Uruguay, and the United Soccer League (USL) with the Ottawa Fury FC, as well as several different Canadian college and university teams.

Richard is presently completing his PhD in Human Health and Nutritional Sciences with a specialty in biomechanics of speed and acceleration training in soccer players, at the University of Guelph (expected 2021). He has presented his research at some of the world’s largest and most prestigious soccer-specific sports science and coaching conferences, including the World Congress on Science and Football, the World Conference on Science and Soccer, the National Soccer Coaching Convention, the Ontario Soccer Summit, and the Futsal Canada Conference.

An avid author, lecturer and coach educator, Richard holds certifications as a FIFA 11+ Instructor, Sport for Life Movement Preparation Instructor, and Ontario Soccer Learning Facilitator.  He works as a Professor in the Fitness and Health Promotion program at George Brown College, and in the Faculty of Kinesiology at the University of Guelph-Humber, provides coaching education for Ontario Soccer, Canada Soccer, and the National Soccer Coaches Association of Canada, and has had over 50 of his articles published in research journals, books, and magazines.

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