Overuse Injuries inYoung Athletes: Causeand PreventionJames H. Johnson, PhDExercise and Sport Studies, Smith College, Northampton, Massachusetts

S U M M A R Y

THE FREQUENCY OF OVERUSE

INJURIES IN CHILDREN HAS

INCREASED IN RECENT YEARS.

INCREASED INTEREST IN SPORTS

AS WELL AS THE INCREASE IN

SPORTS SPECIALIZATION BY

CHILDREN IS ONE CAUSE.

EXTRINSIC AND INTRINSIC FAC-

TORS PREDISPOSE AN INDIVIDUAL

TO OVERUSE INJURIES, BUT ONE

SYSTEMATIC CAUSE IS IMPROPER

TRAINING. OVERUSE INJURIES RE-

SULT FROM REPEATED SUBMAXI-

MAL STRESS FOLLOWED BY

INADEQUATE RECOVERY. CHIL-

DREN INCUR SPECIFIC OVERUSE

INJURIES AS THE RESULT OF

GROWTH. STRATEGIES FOR PRE-

VENTING OVERUSE INJURIES IN-

CLUDE (A) THE USE OF VARIED

PRACTICE TO REDUCE JOINT

STRESS AND ENHANCE LEARN-

ING, (B) PLANNED REST,

(C) GRADUAL PROGRESSION,

AND (D) CROSS-TRAINING.

INTRODUCTION

The practice of athletics in theUnited States has changed sig-nificantly in the last 30 years

(25). Competitive seasons last longer,and athletes often practice all year forone sport. The multisport athlete isalmost a thing of the past, as coachesapply intense pressure on athletes tospecialize in one sport. Even DivisionIII collegiate athletes now have a non-traditional season, playing softball in

the fall or field hockey in the spring.Commensurate with this trend is a dra-matic increase in organized competi-tive athletics for youth (11). Thenumber of additional youth involvedin sport is difficult to measure, but oneestimate suggests that as many as 35million American youth are involvedin sports every year. Moreover, DiFiorihas suggested that the extent of athleticparticipation is more intense (10).

The American Academy of Pediatricshas indicated that there appears to beincreasing numbers of children whospecialize in sport at an early age andtrain all year for that sport (5). Forexample, articles in the New York Timesreported on a small town in Minnesotawhere the basketball coach wanted tostart a ‘‘traveling squad’’ for secondgraders (3). Parents hire privatecoaches for their Little League players(13). These parents believe that im-proved batting makes their childrenbetter applicants for college. There areliterally thousands of club teams play-ing an inordinate number of compet-itions a year. In San Diego alone, thereare more than 125 baseball teams forchildren ages 10 and younger, manyplaying 80 games a year, far more thanmost college teams. The prevailingthought is that if children do notspecialize by the eighth grade, thenthey are not prepared for higher-levelcompetition.

Moreover, the reduction of physicaleducation in the schools combinedwith the health concerns of childrenhas motivated parents to create sports

programs for their own children, oftendeveloping elaborate programs withextensive competition (18). Unfortu-nately, coaches in such programs oftenhave minimal training. Certificationprograms for youth sport coachesoften are cursory at best. In fact,certification is not required in manylocales. There is concern that we placeour most vulnerable individuals (chil-dren) with the least-trained coaches.

The increase in organized competitiveathletics for youth does not comewithout an increased risk of injury.The risk of injury has always been partof athletics, and Pecina and Bojanichave argued that organized sports wereno more dangerous than free play (17).However, children rarely suffer overuseinjuries when they control their ownactivity (10). Overuse injuries, such asstress fractures and patellofemoralstress syndrome, have become rathercommonplace in children (17). Studiesshow that anywhere from 30% to 60%of injuries to children are the result ofoveruse (2,9,26).

OVERUSE INJURIES

The common cause of overuse injuriesis repetitive submaximal loading (27).Overuse injuries occur when an indi-vidual undergoes repetitive stress (suchas in throwing, running, and swim-ming) followed by insufficient rest.The typical response to training is

KEY WORDS :

youth; specialization; overuse; injuryprevention

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adaptation. Muscles, tendons, and lig-aments adapt to the repeated stress ofactivity by getting stronger. But whenbody tissues are presented with toomuch stress, too little recovery time, orboth, the result is just the opposite. Thebody’s ability to recover is over-whelmed. Instead of a stronger body,we get a weaker, injured one (17).

Overuse injuries are pervasive, occur-ring to tendons, bursa, cartilage, bone,and especially the musculotendinouscomponent (17). Stress fractures to thetibia and bones of the foot are the re-sult of overuse. Tennis elbow, osteo-chondroses, Little League elbow, andbreaststroker’s knee are all overuseinjuries. Because overuse injuries arenot acute injuries related to trauma,their diagnosis is difficult, and theyrequire proper medical attention (10).

The causes of overuse injury aremultifactorial. The predisposing factors(Table 1) that lead to overuse injuriesare commonly described as eitherintrinsic (internal to the individual) orextrinsic (external to the individual).We often have less control over in-trinsic factors than extrinsic factors. Forexample, an individual may appear tohave the improper anatomical align-ment to perform a specific sport oractivity, but coaches would be hardpressed to deny participation based onknee alignment.

CHILDREN AND OVERUSE

The fact that children are growing isthe key factor that separates youngathletes from mature athletes. Thereare constant changes in body weight,height, and muscle mass. Growing

bones are more porous but, luckily,they tend to heal quickly (17). Growthcartilage is one of the most importantdifferences between the growing andthe immature skeleton. Growth carti-lage is present at the growth plate(epiphysis) as well as at the muscu-lotendinous insertion. Growth carti-lage is particularly vulnerable to thestress of repeated microtraumas. LittleLeague elbow (medial epicondyle ofhumerus) and Little League shoulder(proximal shoulder) are both overuseinjuries to the epiphyseal growthcartilage (17), Growth for all tissues isnot linear. For instance, the musculo-tendinous unit may develop faster thanthe bone to which it is attached. Sucha condition makes the growth cartilageat this junction more susceptible.Osgood-Schlatter disease (insertion ofquadriceps into the tibia) and Sever’sdisease (insertion of Achilles tendoninto the heel) are 2 examples of overuseinjuries to the musculotendinous in-sertion. Clearly, children are at risk ofspecific overuse injuries related togrowth.

PREVENTION OF OVERUSEINJURIES

Since the latter half of the 20th century,considerable progress has been madeto improve the quality of training (25).Coaches, trainers, and athletes havedevised numerous, creative ways totrain. Schools and communities com-pete to provide the best fitness andathletic facilities. Periodized traininghas become popular, and the variety oftraining equipment is superb. Summertraining camps abound, attracting pro-spective athletes with high-profile

coaches and athletes. Access to train-ing facilities is at an all time high. Theprevailing thought seems to be ‘‘moreis better.’’

But more is not always better, ashuman bodies can only withstand somuch stress. One of the basic problemsis that exercise leaders and coachesoften pay less attention to the otherside of training, recovery (16). Thefocus of prevention should be on thosefactors that we can control. Fortu-nately, many overuse injuries can beprevented. In fact, the American Col-lege of Sports Medicine has suggestedthat about 50% of overuse injuries inchildren and adolescents can be pre-vented (1). Of all the extrinsic factors,improper training methods appear tobe the most frequent cause of overuseinjuries (17). Prevention must start witha careful look at coaching and trainingmethods to bring about the desiredresult without injury. A careful exam-ination of daily practices as well as anassessment of organizing practice overtime is one place to start.

THE WARM-UP

Regardless of the sport, all workoutsand practices should be preceded bya warm-up. In fact, warming up beforeathletic competition or practice isprobably the most common injuryprevention technique used in sport.The classic study by Safran et al. (19)in 1988 showed that muscles that werewarmed by prestimulation were moreresistant to muscle tears than musclesthat had not been previously stimulated.Warming muscles by repeated contrac-tions helped prevent muscle tears.

Table 1Predisposing factors and overuse injuries

Intrinsic factors Extrinsic factors

Anatomic malalignment Improper training methods

Prior injury Poor technique

Poor conditioning Improper surface for practice and competition

Growth Excessive pressure from peers, coaches, and parents

Menstrual dysfunction (irregular or absent menses) Inappropriate equipment—footwear being the most important

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Overuse Injuries in Young Athletes

Increasing the temperature of muscleshas several physiological benefits(Table 2), including improving the speedof muscle contraction and relaxation.Preliminary exercise dilates capillarybeds and increases cardiac output (6).General warm-up and related warm-upare the 2 most common forms of pre-event activity. General warm-up in-cludes such activities as calisthenicsand jogging, whereas related warm-upinvolves participating in the exactactivities one intends to perform whileplaying. General warm-up often pre-cludes related warm-up, but it isimportant that athletes use the exactsame muscles they will use whilepracticing or playing. Related warm-up is generally preferred over generalwarm-up for this reason. Warm-upshould last a minimum of 10 minutes,since it takes that long for muscletemperature to reach a steady state (6).Start the warm-up slowly and pro-gressively increase the intensity.Warming up should not be fatiguing.Remember that not everyone is in thesame state of fitness and warm-upshould be planned accordingly. Afterwarm-up, there should be a briefperiod (3–5 minutes) recovery beforepractice starts.

ORGANIZING PRACTICE TOREDUCE OVERUSE INJURY WHILEIMPROVING PERFORMANCE

Practice is the key to improved sportperformance. In fact, practice is usuallyconsidered the single most importantfactor to learn sport skills (12). Becauseoveruse injuries are normally the result

of high repetition activities, the firststumbling block is how to organizepractice without excess repetition. Cansport (motor) skills be taught withoutexcessive drilling? Providing sufficientpractice time, yet not so much that theathlete acquires an overuse injury, isa daunting task. I recently visited a localtennis club, where a former top-ratedplayer was giving lessons to adoles-cents. He set up ball machines and hadplayers hit 100 forehands followed by100 backhands. He then had them hit50 serves in a row. The pro walkedaround providing feedback and in-struction. The players did improvetheir performance but became quitefatigued and obviously bored. It wasn’tfun to watch and I’m sure it wasn’t funto do. On the surface, one might thinkthat this was good instruction; brandnew ball machines, nice courts, and anenthusiastic teacher seem like a goodidea. But where’s the fun, the motiva-tion, the decision-making? Does any-one ever hit 100 backhands in a rowwhile playing? Further, excess repeti-tions are a recipe for overuse. Researchin motor learning suggests ways thatlearning is enhanced while limitingendless repetition. In fact, teaching bynonstop repetitions may be an inferiorlearning technique.

Vary practice to enhance learningand reduce overuse. Let’s take theexample of our young tennis playerswho are working on backhands, fore-hands, and volleys. Now let’s say thatas the teacher you’re going to devote

30 minutes to stroke work. How youdistribute this 30 minutes of time spentperforming the skill will affect learningas well as joint stress. The literature inmotor learning suggests that thisdistribution is a question of mass vsdistributed practice (22). Massed prac-tice means to run the work periodsvery closely together with little or norest. Distributed practice involves workperiods interspersed with short restintervals. Schmidt and Lee suggest thatdistributed practice is better for per-formance as well as learning. In fact,they even suggest that longer restperiods are better than shorter ones(22). An important factor during prac-tice is fatigue. Fatigue increases musclestrain, reducing the ability of themuscle to absorb energy (14). Distrib-uted practice (like interval training)tends to reduce fatigue, allowing mus-cle to absorb force and protect jointsmore easily. Distributing learning ac-tivities by interspersing rest with workis great for learning and injuryprevention.

A second question regarding practice isthe sequencing of drills. In our exam-ple, the players hit all forehands,followed by backhands, etc. Thispractice technique is often labeled asblocked practice. Hitting numerousbackhands in a row is stressful whetherit’s massed or distributed, especially ifthe player is young and not biome-chanically correct. Random practice isjust the opposite, mixing up forehands,backhands, and volleys. Random prac-tice is an example of contextual in-terference, first presented in a study in1979 (23). Schmidt and Lee (22) reportthat the immediate acquisition ofperformance is better when practiceis presented in a blocked fashion. How-ever, retention of the motor task is bet-ter with random practice. When askedto repeat the task(s) at a later date,subjects who practiced in a randomfashion were superior in performance.

The classic report by Schmidt in 1975supports varying practice to bringabout the desired result. Schema the-ory suggests that people developgeneralized motor programs. In fact,

Table 2Benefits of warm-up

Muscles contract faster

Muscles relax faster

Economy of movement is improved

Metabolism is enhanced because of the increased temperature of muscle tissue

Muscle blood flow is increased

Provides a last minute practice session

Athletes prepared psychologically for performance

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Schmidt’s ‘‘schema Theory’’ suggestedthat people will learn more quickly ifthey practice a task in a variety ofsituations, like throwing a ball butdifferent distances each time. More-over, practice that lacks variety is lessinformative to the learner (20). Wulf(28) has extensively studied schematheory and concluded that varyingpractice works well with children.

Further support of the variation ofpractice has come from ‘‘The GamesApproach.’’ Martens has suggestedthat the overemphasis on technicalskills as well as excessive use of directinstruction reduce decision making andincrease boredom. Martens recom-mends this approach as an alternativeto traditional teaching methods. Thegames approach involves more specifictraining, that is, practice is more gamelike. Martens asks the question ifhaving a baseball player hit 50 ballsat a time prepares them for a gamewhen they only have 3 strikes. Martensargues that the games approach is verymotivating and that practice may makemore sense when the athlete connectspractice with play (15).

Because the cause of overuse injuries isexcessive repetition without recovery,it would appear that conventionalteaching methods, involving repeateddrills of the same activity, is unwar-ranted. A practice session that involvesvariety allows more time for recovery,less fatigue, and produces desirablelearning effects. Indeed, practice thatis fun and uses game-like activities mayalso encourage continued participation.

MEASURE PROGRESSION TOREDUCE OVERUSE INJURY

Coaches, teachers, and trainers shouldbe able to quantify any practice.Quantifying workouts provides leaderswith a method of measuring progres-sion. Track and swim coaches cancount distance, strength coaches cancount repetitions and tonnage, andtennis coaches can count time on task.Regardless of the sport or trainingtechnique, quantification is possibleand necessary.

Gradual progression. Gradual pro-gression is one of the most importantprinciples in the prevention of overuseinjuries. The most frequent trainingerror is a rapid change in volume andintensity. Because the goal of training isimproved performance, a training pro-gram that creates injuries (that takeconsiderable time to heal) seemspoorly planned. Interestingly, this isoften not the coach’s fault. One of ourcoaches was recently surprised whenhe found one of his soccer teammembers running on the treadmill at10:00 p.m. Normally, this would befine, but the soccer preseason was infull swing. The athlete was concernedabout her fitness and decided to dosome extra work. Athletes are oftenhighly motivated to get in shape andtend to be impatient. This is whencoaches and trainers need to havea firm hand, to know when to stopor slow down.

One common suggestion is the 10%rule (9,10). For example, if a swimmeris doing 3,000 yards 1 week, theyshould do no more than 3,300 yardsthe next week. Although this is a con-venient guideline, not everyone canwithstand a 10% increase and suchchanges may need adjustment. Howmuch yardage is enough? In onethorough review of overuse injuries,the authors suggest that ‘‘mileagemania’’ is the cause of many overuseinjuries, especially stress fractures (17).Coaches must continuously monitortheir athletes for soreness, perfor-mance, lethargy, and boredom. Whenathletes are excessively sore and per-forming badly, more exercise is oftennot the answer.

Changing surfaces. Changing surfa-ces is often problematic for athletes.Let’s say a group of runners has beentraining on a long distance dirt pathand move to an artificial track surface.Although such a training strategy maybe recommended, a typical error is thatathletes are often asked to repeat thesame workout performed on theirfamiliar surface. Any change in surfacewill place additional demands on the

musculoskeletal system. Running ona beach might be fun but a bad idea ifathletes are required to run theirnormal distance. When changing sur-faces, athletes need to reduce theamount of work until they adapt.

Periodized training. Periodized train-ing is a powerful strategy to improveperformance and reduce overuse injury.Periodization requires planning withspecific seasonal as well as annual goals.Periodization plans involve a gradualprogression in activity designed for theathlete to peak for specific activities.Moreover, periodization involvesplanned rest, whether annually orweekly. Easy workouts are planned tofollow hard workouts. After peak peri-ods of training, the plan calls for athletesto back off, possibly cross train, to getaway from their primary sport oractivity. Planned rest allows for fullrecovery and adaptation (4).

SPECIALIZATION

The role of early specialization remainsa source of controversy in exercisescience. Unfortunately, the improba-bility of reaching championship per-formance does not seem to discouragemany children (and their parents) fromaspiring to be Olympic champions orNBA players. Scores of children lose outon the diversified development gainedby participating in a variety of sports.The American Academy of Pediatricshas stated that ‘‘Young athletes whospecialize in just one sport may bedenied the benefits of varied activitywhile facing additional physical, phys-iologic, and psychologic demands fromintense training and competition’’ (8).

Clearly, one question we need to ask iswhether the increased interest inspecialization and competition reducesphysical activity in later life. A com-mon goal stated to support youth sportprograms is the promotion of lifelongphysical activity. We now frequentlyread about overtraining, staleness, fa-tigue, burnout, and overuse injuries.There are a number of burnout theo-ries, but the common theme is over-training (7,21,24). This overtraining

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Overuse Injuries in Young Athletes

syndrome is often defined as a succes-sion of psychological and physiologicalchanges that result in reduced perfor-mance (5). Burnout has been welldescribed in the literature for adultathletes. Simply put, athletes who burnout tend to quit, some never to return.Far less is known about burnout inchildren, especially the effects of sportspecialization. In a recent review,Brenner suggests that burnout mayhave a detrimental effect on life-long physical activity (5). Does sportspecialization for children promotelifelong activity? Because sport special-ization is a rather recent phenomenon,not enough data exist to answer thisquestion.

Leaders of children’s sports are oftenwell meaning, but occasionally ill in-formed. Coaching practices are oftenbased on adult models, historical pre-cedence, and anecdotes. Coaches andleaders of children’s sports need basicknowledge of growth and develop-ment, pedagogy, and exercise science.Further, they need to apply this in-formation to youth sport.

RECOMMENDATIONS TO REDUCEOVERUSE INJURY

� When teaching sport skills, reduceendless repetitions of the same task.

� Teach motor skills in a distributedmanner, interspersing frequent restperiods with work periods.

� Use random practice, mixing upactivities so that the same activityis not repeated excessively.

� Use frequent games to vary practiceand enhance motivation.

� Keep workouts interesting and age-appropriate.

� Gradually increase progression ofthe workload.

� Monitor athletes for fatigue, sore-ness, and general apathy.

� Take care to reduce workload whenchanging surfaces.

� Periodize training on a weekly andseasonal basis.

� Take 1–2 days of absolute rest eachweek.

� Schedule breaks every 2–3 monthswith a change in activity.

� Encourage children to participate ina variety of sports.j

James Johnson isProfessor of Exerciseand Sport Studies atSmith College, North-ampton, Massachusetts.

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