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Overuse injuries have become common as more and more children participate in sports. A careful history can identify risk factors; targeted patient education can lead to successful rehabilitation and prevent injuries.
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Overuse injuries have become common as more and more children participate in sports. A careful history can identify risk factors; targeted patient education can lead to successful rehabilitation and prevent injuries.
Thanks to the growing number of young people participating in sports at an early age, training year-round, and competing at specialized or elite levels,1 the incidence of overuse injuries has risen in the past decade. Recent studies estimate that 30% to 50% of pediatric sports injuries are caused by overuse, with the frequency of injury equal among boys and girls.2,3
Ideally, children should participate in sports for one reasonto have fun. Along with that fun should come the pride of acquiring and mastering new skills in a social environment. Regrettably, lack of fun is often a leading reason for dropping out.4 [Editor's note: For an in-depth discussion of the psychosocial aspects of sports participation, see "Youth sports: More than sprains and strains" in the March 2001 issue.]
Understanding both the intrinsic and extrinsic demands placed on the young athlete can help you identify risk factors for overuse injuries. Identifying these concerns is often a rewarding part of an injury evaluation and can have a significant impact on your patient's physical and mental health.
Always maintain a high level of suspicion for problems caused by overuse. Even the most innocent-appearing injury may have elements of overuse, so a meticulous history is necessary to identify at-risk patients and provide appropriate guidance. In this article, I present case examples to highlight the role of the pediatrician in detecting and treating these injuries. But first, a brief review of what constitutes overuse.
In simple terms, overuse injuries can be defined as the product of "too much, too fast, too soon."5
How much is too much? How fast is too fast? How soon is too soon? The answers vary from athlete to athlete. A program that overtaxes one participant may be acceptable to another of the same age and ability. Certain characteristics, however, can clue you in to possible overtraining or overuse.
Mild discomfort or soreness after physical activity, rating no higher than 2 or 3 on a pain scale of 0 to 10, is common. If pain exists during activity, or if pain after activity rates higher than 3, that activity is perhaps "too much," "too fast," or "too soon" for that particular athlete.6
The use of ice and nonsteroidal anti-inflammatory drugs (NSAIDs) immediately after exercise is common. But the need for increasing amounts of ice or NSAIDS, or the need to use them for a longer duration, should raise the suspicion of overuse. If pain or soreness causes changes in gait, body mechanics, or sport technique, this too may suggest overuse. Other signs of a possible problem include diminished success or enjoyment in sports participation and changes in mood, peer relations, or school and work performance.
Children should never "play through" any pain or disability.1 Regrettably, because they fear being removed from activity or disappointing parents and coaches, many young athletes continue painful activities.7 Parents and coaches must learn to temper their desire to "let the child continue to play" and seek early and appropriate care to prevent long-term consequences.
Rehabilitation of any injury follows a three-step process (Table 1). During this process, focus on what the athlete can do rather than what the athlete can't do. Complete cessation of activity is often unnecessary and unlikely to be followed by a child athlete committed to his sport.1
Physical therapy: Power and endurance exercise
Sport-specific functional progression
Focus on technique and skill instruction
Criteria for advancement
No pain, full range of motion with normal flexibility
Normal strength and strength balance
Good fitness with normal sports mechanics
Demonstration of sport-specific skills
Source: Herring SA et al3
You are seeing a brother and sister for their annual physical exams. The 11-year-old boy is an all-star pitcher on three different teams and throws more than 100 pitches a week. His 8-year-old sister has begun swimming twice a day in a competitive swim program.
Preparticipation or annual exams are excellent opportunities to identify potential overuse situations. Both these athletes are at high risk of shoulder and elbow injuries seen in overhead activities such as throwing or swimming, where arm motion occurs at points above the head and shoulder girdle.
The absence of finite participation limits for young athletes is a growing risk factor for overuse injuries. While 6- to 9-year-olds may have developed important visual, balance, motor, and learning skills that allow for organized sport participation,8 there is a growing tendency to push such young athletes toward sport specialization and training regimens suited for more mature athletes.2 Children under 10 years should avoid specializing in one sport and participate in a variety of activities with other children who are appropriately matched in age, ability, and interest.1
Experience indicates a direct relationship between the number of pitches thrown or time spent swimming a week and shoulder or elbow pain.911 Specific recommendations regarding age and number of pitches thrown or frequency and duration of swimming have been developed (Tables 2 and 3) and should be followed precisely. All pitches or meters count, whether in games or competition, in practice, playing with friends, or in private lessons.
|Age (yr)||Pitches permitted (per game)|
|810||52 +/- 15|
|1112||68 +/- 18|
|1314||76 +/- 16|
|1516||91 +/- 16|
|1718||106 +/- 16|
|Age (yr)||Frequency and duration of swim||Development|
|57||2 sessions/wk of 2060 min||Introduce basic water skills and stroke technique|
|89 and technique||2 or 3 sessions/wk of 4560 min||Develop more advanced skills|
|1012||35 sessions/wk of 6090 min||Introduce competition, improve technique|
|1316 strokes over various distances||59 sessions/wk of 90120 min||Maximize development of all|
Because the throwing motion involves both the shoulder and elbow, evaluate the elbow in shoulder injuries and the shoulder in elbow injuries. Remember that shoulder and elbow pain are not limited to pitchers. Other high-volume throwing positions include catcher and shortstop. Be extremely suspicious of injury in a pitcher who plays these other positions when not on the mound.
The goal of exercise is to apply repetitive submaximal loads to connective tissue, muscle, and bone to build strength and endurance.2 Because the beneficial aspects of exercise actually take place during the recovery phase, adequate rest is essential to allow tissue to adapt and undergo further activity without injury.1 Instruct the patient to take at least two full rest days a week, with a minimum of two rest days immediately after a pitching performance.11 This advice may be contrary to participation in weekend tournamentsstaples of youth sports in which athletes are often required to perform several times in a two- or three-day period.
Excessive demand and insufficient recovery result in tissue microtrauma with release of vasoactive substances, inflammatory cells, and enzymes that create clinical symptoms of pain, weakness, and diminished range of motion.3 In overhead sports, too much activity leads to fatigue of the supporting rotator cuff muscles, allowing for increased movement of the humeral head within the glenoid fossa.
In early phases of overuse, pain is vague and noted only with activity. Further progression leads to more sharp, localized pain during activity and at rest (Table 4). Besides pain, signs of shoulder or elbow weakness include decreased accuracy, endurance, and throwing velocity. Technical errors such as "dropping the elbow" during the acceleration phase of throwing or the out-of-water recovery and catch phases of freestyle swimming can also lead to fatigue of rotator cuff muscles.9,11
|Type 1||Pain after activity only|
|Type 2||Pain during activity, not restricting performance|
|Type 3||Pain during activity, restricting performance|
|Type 4||Chronic, unremitting pain|
Because of the valgus stresses placed on the elbow in throwing motion, athletes under 14 years of age, who have immature ligament and tendon attachments to the medial epicondyle apophysis, are at greater risk of injury than older athletes. Growth of the longitudinal bone occurs sooner than that of ligament, muscle, or tendon, creating an imbalance that places undue stress on the immature cartilage of these apophyseal attachment sites.1
Shoulder examination. Ask the athlete to remove his (or her) shirt or to wear a tank-top during the examination. Then begin the exam by noting any muscle asymmetry or underdevelopment. Full active motion of both shoulders should be painless, smooth, and coordinated. Assess external rotation by having the athlete place both arms, one at a time, behind the head and reach down the thoracic spine as far as possible. Internal rotation is measured by having the athlete place both arms (again, one at a time) behind the back and "scratch" the back as high as possible with his hands. As always, compare the injured and noninjured sides.
Test supraspinatous strength and function by having the athlete "pour out two cans of soda" with both arms abducted to 90º and forward flexed to 30º, thumbs pointing to the ground (Figure 1). Inability to hold the arm in this position suggests a complete supraspinatous tear. Measure strength by placing a downward stress on the arms. This can be done with both arms simultaneously or one arm at a time.
Test the subscapularis (anterior cuff) and infraspinatous and teres minor (posterior cuff) muscles by having the athlete flex both elbows to 90º while locking both elbows against the side of his body. External rotation against resistance stresses the infraspinatous and teres minor, while internal rotation stresses the subscapularis (Figure 2).
The infraspinatous can be further evaluated by the lift-off test (Figure 3). Have the athlete flex the elbow to 90º and place the dorsum of his hand against his lumbar spine. Provide resistance as he tries to lift his hand off his back. Total inability to perform the lift-off test suggests a complete infraspinatous tear.
To assess stability of the glenohumeral joint, have the athlete abduct the arm and flex the elbow both to 90º. Push the elbow in a posterior direction and see if the resulting anterior motion of the humeral head causes apprehension (Figure 4). Positive findings indicate abnormal anterior laxity of the humeral head within the glenoida common finding in young athletes with rotator cuff weakness and fatigue.
Standard anterior-posterior and lateral (scapular-Y or outlet views) radiographs should be obtained to rule out bone pathology, although in most cases these studies are unremarkable.
If complete rotator cuff tear is suspected or the athlete has continued limitations despite adequate rest and rehabilitation, referral to an orthopedist or sports medicine physician is warranted.
Elbow examination. The throwing elbow may have limited extension compared with the nonthrowing elbow. This is normal in an adult thrower, but any extension deficit in a young pitcher is significant. Tenderness is often elicited on the medial epicondyle and distally along the medial (ulnar) collateral ligament, and can be accentuated by placing a valgus stress on the elbow. Resisted wrist flexion may also increase the pain because the wrist flexors originate on the medial epicondyle.
Four radiographic views of the elbow (anterior-posterior, lateral, and medial and lateral obliques) are routinely ordered to evaluate the joint in a young thrower. Because ossification of the six secondary growth centers around the elbow is greatly variable, consider obtaining comparison views of the noninjured elbow or referring the young thrower to a sports medicine physician for further evaluation.
Shoulder and elbow rehabilitation and "prehabilitation." Specific rehabilitation includes limiting overhead activity, often for several weeks. Playing a nonthrowing position like first base may be acceptable if the play is pain-free; a swimmer can run or bicycle to maintain endurance. Ice (for 20 minutes) and NSAIDs can be used during the initial rest period and after rehabilitation activities to reduce swelling and discomfort.
Once the athlete regains normal range of motion, emphasis should be placed on strengthening the rotator cuff muscles (Figure 5) and the scapular-stabilizing muscles (Figure 6), and on strengthening the wrist flexors for medial elbow support. These exercises can also be used for prehabilitation to strengthen the shoulder and prevent injury. Teaching these exercises during a preparticipation or annual exam can reduce the likelihood of an injury visit later in the season. Mechanical errors such as dropping the elbow or poor stroke technique can complicate matters, so have an experienced coach review and correct such mistakes.
A 14-year-old high school freshman comes in for evaluation of symptoms of an upper respiratory infection. You congratulate him on the successful football season that ended recently. He tells you that he started wrestling the day after football ended and admits to increasing back pain over the past few weeks.
There are two major teaching points in this vignette: First, asking about sports participation at every visit creates rapport and might even reveal relevant concerns. Second, back pain in a child or adolescent must be taken seriously.
Frequent back extension (heading a soccer ball, gymnastics, line play in football) places axial loads that stress the posterior elements of the lumbar column, often leading to stress injury of the pars interarticularis, most often at L5.12
This 14-year-old also exhibits other key risk factors for stress or overuse injury:
He recently increased training. Bone stress appears to peak three weeks after initiation of a more intense training regimen.13 Pertinent examples include novice or previously sedentary athletes just learning a new sport or more experienced athletes reaching a new level of play (freshmen in high school, for example).
He is in the midst of a growth spurt (boys, between 13 and 15 years; girls, between 11 and 13 years).
He did not allow sufficient rest and recovery between sport seasons. Optimally, athletes should take at least one week off between seasons. Many do not heed this recommendation.
The spectrum of lumbar region injury runs from a pre-stress reaction (lumbar pain without true fracture) to frank unilateral or bilateral spondylolysis (true stress fracture of the pars), culminating in spondylolisthesis (anterior motion of a lumbar segment relative to the next distal segment).12
Spondylolysis often presents as midline lower lumbar pain of insidious onset with gradual worsening. Extension or rotation of the lumbar region often exacerbates the pain. Radiation of pain to the lower extremities or other neurologic symptoms suggests alternate diagnoses. The straight-leg hyperextension test (stork test) helps screen for this disorder. Have the patient stand on one leg and raise the other leg straight out in front while leaning backwards. Lumbar pain on the stance side suggests spondylolysis.
Tight hamstring muscles, which increase lumbar lordosis, have been identified as a causative factor in spondylolysis.3 To document hamstring flexibility, measure the popliteal angle: Place the patient in a supine position, and place the hip in 90º of flexion. Then attempt to passively extend the knee. The popliteal angle is the angle formed between the extended lower leg and the back of the thigh. Ideally, the angle should be between 135° and 180°, but many adolescents with tight hamstrings have a popliteal angle of about 90°.
Radiologic imaging and subsequent management of suspected spondylolysis are controversial. Many texts call for initial radiographic studies to include lumbar anterior-posterior, lateral, and bilateral oblique views; others question whether the value of these studies, given their limited specificity and sensitivity, outweighs the risk of exposing the gonads to radiation. Additional imaging studies, such as single-photon-emission computerized tomography (SPECT) scans or CT scans, may be indicated to determine acuity and delineate fracture pattern, respectively. Therefore, referral to spine specialists is highly recommended.3,14,15
Rehabilitation strategies include bracing to limit lumbar extension, abdominal strengthening, and hamstring flexibility (see the discussion of knee pain in the following section). Often, athletes must refrain from at-risk activity for at least three to six months.12
A 16-year-old cross country runner reports bilateral leg pain. She recently began more intense hill workouts and running more miles each week. She had a tibial stress fracture last season. Her mother is worried because after two years of regular menstrual periods, her daughter has had only two periods in the past eight months.
Runners with leg pain often suffer from one of three entities: anterior knee pain, shin pain, or Achilles tendon and heel pain. These can be the cumulative result of increases in midseason training that overtax young athletes. In general, the intensity, duration, and frequency of training should not be increased by more than 10% in a given week. So, a runner who runs 20 miles a week should run no more than 22 miles the next week at the same pace without adding hills or sprint work.1 Table 5 lists specific age-based recommendations for maximum running distances.
|Age (yr)||Distance (km)|
Always review the course of previous injury to the affected region. Multiple minor injuries or repeated injuries to the same area are signs of inadequate rest and rehabilitation. The highest risk factor for subsequent injury is incomplete rehabilitation of a primary injury. Athletes with first-time injuries should therefore diligently rehabilitate before returning to play.3
Pay special attention to a history of stress fractures anywhere in the body. In a female athlete, such a history may be the only obvious sign of the female athlete triad of osteoporosis, menstrual irregularities, and an eating disorder.16 Although no athlete is immune from the consequences of inadequate nutrition, a young woman who participates in an endurance activity or "appearance" sport such as figure skating and gymnastics is at particular risk.2
Substantial physical activity coupled with inadequate caloric and protein intake can lead to primary amenorrhea (no sexual development by 14 years of age or no menarche by 16 years) or secondary amenorrhea (three or more months between periods or fewer than six periods in 12 months). Such "athletic" amenorrhea is a diagnosis of exclusion made only after complete evaluation and exclusion of other causes. The consequences of amenorrhea include decreased circulating estrogen levels, leading to osteopenia or osteoporosis with an increased risk of stress fracture.16
Active youth, particularly adolescents undergoing a growth spurt, often have astounding caloric needsas many as 4,500 kcal/d.17 Aside from optimal caloric intake, the most crucial nutritional issues surround adequate calcium, iron, protein, and fluid intake (Table 6). Elicit a diet history or three-day diet log, or encourage the patient to consult with a nutritionist to promote appropriate lifetime eating practices.18
Before exercise: 16 oz
1530 min before starting
During exercise: 48 oz
every 15 min
After exercise: 16 oz for every
pound of body weight lost
1,200 mg/d for ages
1124 yr (US RDA)
1,500 mg/d for
Anterior knee pain. In immature athletes, frequent knee extension can lead to traction apophyseal injury with local tenderness at secondary growth centers of the distal patellar pole (Sinding-Larsen-Johansson disease) and the tibial tubercle (Osgood-Schlatter disease). Postactivity ice massage to these painful areas can be of great benefit.
Patellofemoral pain syndrome (PPS) can affect an athlete of any age. It is characterized by complaints of vague pain around or underneath the patella that worsens with prolonged running, standing, or sitting in a chair. Swelling and frank instability are uncommon, though the patient may feel that the knee "collapses" due to the anterior knee pain. The exact mechanism of PPS is uncertain, but many believe that malalignment of the patella about the distal femur is the main problem. Weak or uncoordinated quadriceps muscles, especially the vastus medialis oblique (VMO), can lead to abnormal lateral movement of the kneecap or excessive contact of the patellar undersurface with the femur, both leading to pain.
Start the exam by focusing on the knee alignment in stance. Pronounced valgus knee alignment and underdeveloped quadriceps (especially the VMO) are particular risk factors for PPS. On manual examination, there is significant pain on patellar compression or excessive lateral translation of the patella. There should be no sign of ligament instability or meniscus injury.
Tight hamstrings can be a root cause of anterior knee pain by placing greater resistance on the extensor mechanism. Increasing hamstring flexibility is the cornerstone of rehabilitation (Figure 7). VMO strengthening can help in some cases (Figure 8). Correction of hyperpronation (see the discussion under shin pain that follows) can also help alleviate symptoms. Ice and NSAIDs can be used to reduce inflammation and discomfort.
Initial presentations of the syndromes just discussed usually do not require radiographic evaluation. Cases resistant to therapy might warrant radiographic examination or specialty consultation.
Shin pain. Repetitive eccentric contractions of the foot dorsiflexors during heel strike in running can lead to medial tibial stress syndrome (so-called shin splints), an inflammatory condition of the tibialis posterior and soleus muscle aponeurosis-periosteal interface at the medial border of the tibia. With this syndrome, there is no numbness or tingling in the lower leg or foot.
Further along the continuum are tibial stress fractures, most frequently found on the medial border of the distal tibia. Whereas shin splint pain is usually diffuse and occurs on the medial border of the tibia and the surrounding soft tissue, pain from a tibial stress fracture tends to be focal (the athlete can often identify the painful area with the tip of a finger) and localized more toward the tibial spine than toward the surrounding soft tissue. Another differentiating factor is that activity actually reduces the discomfort of shin splints, while repeated impact activity intensifies the pain of a tibial stress fracture.
Evaluation of shin pain includes assessment of midfoot hyperpronation (excessive collapse of the medial foot arch in stance). Excessive pronation can increase tibial internal rotation during weight-bearing, placing greater demands on the tibialis posterior and soleus.10 Assess the presence of pronation by having the patient walk barefoot across the examination room while you look for collapse of the medial arch. Further evaluation includes careful palpation of the tibia and surrounding soft tissue to identify origins of the pain.
Most cases of shin splints and tibial stress fractures are non-emergent; the exceptions are patients who have focal pain localized to the proximal tibial spine. Because stress fractures of the anterior tibial cortex are more likely than other fractures to become complete fractures, patients with such focal pain should be placed on non-weight-bearing status and immediately referred for orthopedic consultation.
Although plain radiographs have suboptimal sensitivity for stress fractures, they remain the method of choice for initial investigation. Standard views include anterior-posterior, lateral, and bilateral oblique views of the tibia and fibula. Periosteal elevation and cortical irregularities are common "soft" findings in suspected stress fractures. Triple-phase bone scans have greater sensitivity and specificity for both medial tibial stress syndrome and stress fractures, and are often part of specialty consultation.15
Treatment includes limiting impact activities such as running and jumping and using medial arch supports to correct hyperpronation. Nonimpact endurance activities such as biking, swimming, or pool-running (in which the person wears a floatation vest that allows a running motion while "floating" in the pool) are excellent alternatives during the healing phase. Ice massage on the painful regions can help ease the discomfort of shin splints.
Achilles tendon and heel pain. The Achilles tendon has been termed "the thermometer of the runner"when a light squeeze produces pain, the runner has almost certainly been overtraining.19
Achilles tendinosis is caused by chronic overload of the gastrocnemius and soleus muscles during push-off, resulting in degenerative changes within the collagen substance of the tendon.20 This condition is usually seen in more mature adolescent and adult athletes. Athletes between 8 and 12 years are more apt to have Sever disease, focal tenderness and inflammation of the Achilles tendon insertion (rather than the tendon itself) into the apophyseal region of the calcaneus.
Evaluate midfoot pronation, because hyperpronation can place increased stress on the Achilles tendon and the calcaneal insertion. Test passive dorsiflexion, which, ideally, should be greater than 10º, by first placing the foot in a supinated position and then moving it into the dorsiflexed position. Limited dorsiflexion is another key risk factor for pain. In Achilles tendinosis, maximum tenderness is found in the distal tendon midsubstance, whereas Sever disease produces tenderness at the posterior calcaneus with occasional radiation to the plantar surface of the foot.
Radiographic examination is usually not indicated. The recovery period can be prolonged, with treatment focused on stretching of the Achilles and the initial use of heel cups or wedges to reduce the impact on the Achilles-calcaneus insertion. Ice massage to the body or calcaneal insertion of the Achilles tendon can be beneficial, and NSAIDs can reduce pain and swelling.
Overuse injuries are a growing component of a general pediatric practice. A careful history and evaluation can often identify root causes and provide the opportunity to offer the athlete tips on rehabilitation and injury prevention. Focusing on more common conditions characterized by overuse (Table 7) can help guide the initial evaluation and treatment while reducing morbidity in an active population.
|Rotator cuff tendinosis||Too much overhead activity, weak rotator cuff muscles, poor form||Assess rotator cuff strength and sport technique||Strengthen rotator cuff and scapular muscles|
|Glenohumeral laxity||Same as above||Perform shoulder apprehension test||Same as above|
|Medial elbow pain||Excessive throwing, weak arm flexors, poor technique||Assess valgus laxity of elbow, obtain radiographs||Rest, strengthen arm flexors assess and correct technique|
|Spondylolysis, spondylolisthesis||Repeated hyperextension, poor hamstring flexibility||Perform stork test, obtain radiologic imaging||Increase hamstring flexibility +/- bracing (referral)|
|Sinding-Larsen-Johansson disease, Osgood-Schlatter disease||Immature apophyseal regions, tight hamstrings||Palpate regions of tenderness, measure popliteal angle||Begin ice massage, increase hamstring flexibility|
|Patellofemoral pain syndrome||Weak quadriceps (especially, VMO), tight hamstrings||Measure popliteal angle, perform patellar compression, assess lateral movement||Hamstring stretches VMO strengthening, possibly apply patellar bracing or taping|
|Medial tibial stress syndrome (aka shin splints)||Dorsiflexor weakness, too much impact, hyperpronation||Assess for diffuse tenderness on medial tibial border and midfoot hyperpronation||Reduce impact activities begin ice massage, correct hyperpronation|
|Tibial stress fracture||Too much impact, hyperpronation, possibly eating or menstrual disorder||Assess for focal pain on examination, order radiographic exams, obtain nutrition and menstrual history||Possibly, put patient on nonweight-bearing status limit impact activities|
|Achilles tendinosis||Tight dorsiflexors, too much running or jumping||Assess for focal pain at Achilles tendon on examination, limited dorsiflexion, and hyperpronation||Limit impact activities increase dorsiflexion use heel cup/wedge begin ice massage|
|Sever disease||Same as above, plus the patient is age 812||Assess for pain at Achilles insertion into posterior calcaneus limited dorsiflexion, and hyperpronation||Same as above|
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3. Herring SA, Kibler WB, Press JM: Functional Rehabilitation of Sports and Musculoskeletal Injuries. Gaithersburg, Md., Aspen Publishers, 1998
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8. Tanner SM: Growth and developmental concerns for prepubescent and adolescent athletes, in Sallis RE, Massimino F: ACSM's Essentials of Sports Medicine. St. Louis, Mosby-Year Book, 1997
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11. Whiteside JA, Andrews JR, Fleisig GS: Elbow injuries in young baseball players. Physician and Sportsmedicine 1999;27:91
12. Gerbino II PG, Michelli LJ: Spondylolysis and spondylolisthesis, in Sallis RE, Massimino F: ACSM's Essentials of Sports Medicine. St. Louis, Mosby-Year Book, 1997
13. Moriarity JM: Injuries in football and soccer, in Sallis RE, Massimino F: ACSM's Essentials of Sports Medicine. St. Louis, Mosby-Year Book, 1997
14. Herring SA: Spondylolytic injuries in the young athlete. Symposium Lecture, American Medical Society for Sports Medicine Annual Meeting, San Diego, 2000
15. Jimenez CE: Advantages of diagnostic nuclear medicine. Physician and Sportsmedicine 1999;27:45
16. Joy E, Clark N, Ireland ML, et al: Team management of the female athlete triad. Physician and Sportsmedicine 1997;25:65
17. Kleinman RE (Ed): Pediatric Nutrition Handbook, ed 14. Elk Grove, Ill., American Academy of Pediatrics, 1998
18. Williams MH: Nutrition for Fitness and Sport, ed 4. Dubuque, Iowa, William C. Brown Publishers, 1995
19. Fields KB: Running, in Sallis RE, Massimino F: ACSM's Essentials of Sports Medicine. St. Louis, Mosby-Year Book, 1997
20. Khan KM, Cook JL, Taunton JE, et al: Overuse tendinosis, not tendonitis. Physician and Sportsmedicine 2000;28:38
Chris Koutures. An overview of overuse injuries. Contemporary Pediatrics 2001;11:43.