Introduction
Overview
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Track and field often attracts multisport athletes.
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The sport involves year-round competition and training.
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Differing athletic events subject athletes to differing demands. For example:
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The shot put demands explosive power.
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Endurance events demand high levels of aerobic conditioning and stamina.
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Sprint distances (100 m, 200 m, and 400 m) demand explosive conditioning for power, flexibility, and anaerobic conditioning.
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Middle distance races (800 m or 1500 m) demand a combination of anaerobic and aerobic conditioning to sustain power and stamina.
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Distance events (3,000 m, 5,000 m, 10,000 m, and marathon) demand stamina, high levels of aerobic conditioning, and sustained power.
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The 100 m and 400 m hurdles, as well as relays (4×100 m, 4×200 m, 4×400 m, 4×800 m, 4×1500 m, distance medley, and sprint medley), demand mental concentration, power, and stamina.
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Field events, such as long jump, high jump, triple jump, shot put, javelin, discus, hammer, heptathlon, decathlon, and pole vault, as well as the track event 3000 m steeplechase, demand combinations of technique, stamina, power, and speed.
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Epidemiology
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It is difficult to look at injury statistics given the lack of a common denominator (player hours or athlete exposures) as well as variability in methodology of studies.
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There are no National Collegiate Athletic Association (NCAA) data collected for track and field.
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For large track and field events, injury incidence is the greatest for minor orthopedic injuries (5.7 per 1,000 athletes), followed by minor medical injuries (3.4 per 1,000 athletes). Medical coverage should be planned to accommodate seven major orthopedic injuries and two major medical injuries per 10,000 athletes.
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Male athletes and masters athletes are at greater risk of injury than other categories of athletes.
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Of all participants in the 1985 Junior Track Olympics, 35% reported the need for performance-related medical treatment.
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In general, most injuries are overuse injuries that occur during training. However, the risk of injury during competition is four times higher than that in training.
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Acute injuries are often muscle strains or avulsions or are related to stress fractures; other acute injuries uncommon.
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Majority of injuries involve lower extremities.
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There is some risk for head and neck injury during the high jump and pole vault; there is a risk of blunt trauma with javelin, hammer, and discus.
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Of particular concern are acute medical problems such as cardiovascular collapse secondary to underlying cardiac disease, dehydration, or other abnormalities related to environmental conditions.
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Site of Injury
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The most common injury sites are the lower leg (28%), thigh (22%), and knee (16%).
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The most common injuries are hamstring muscle strains and stress reactions.
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The knee is the most commonly injured joint in runners (48% of all joint injuries).
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Overuse injuries are more common in distance runners, whereas acute injuries are more common in sprinters, hurdlers, jumpers, and multievent athletes. Recurrent injuries are common.
Specific Diagnoses
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Anterior knee pain accounts for 24% of running injuries in men and 30% of running injuries in women.
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Medial tibial stress syndrome accounts for 7.2% of injuries in men and 11.4% in women.
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Iliotibial band syndrome accounts for 7.2% of injuries in men and 7.9% in women.
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Patellar tendinosis accounts for 5.1% of injuries in men and 3.1% in women.
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Metatarsal stress syndrome accounts for 3.1% of injuries in men and 3.8% in women.
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Achilles tendinosis accounts for 4.7% of injuries in men and 2.7% in women.
Musculoskeletal Issues
Basic Running Mechanics
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It is important to understand the normal biomechanics of running to recognize abnormal biomechanics and how they can affect incidence of injury.
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Foot strike: At lower speeds, occurs with the heel, but at higher speeds, occurs with the forefoot
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Ground strike occurs 800 to 2,000 times per mile for the average runner (5,000 foot strikes per hour of running).
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Reaction forces at foot strike are usually 1.5 to 5 times the body weight. Joint shear forces during running increase to almost 50 times that of walking. These reaction forces are augmented considerably by different surface types.
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At the point of initial rearfoot contact, the foot is in supination. This is associated with the “closed-pack” position, a rigid positioning of the tarsal bones increasing stability.
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The foot then pronates with the tarsal joints, assuming an “open-packed” position, which is more accommodating and less rigid, allowing partial absorption of reaction forces. There is internal rotation of the tibia on the talus.
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As runners progress to the push-off, the subtalar joint supinates with external rotation of the tibia. The foot remains in supination during the airborne phase and forward swing of leg.
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Major muscle groups all show increased electromyographic activity during running, and all lower extremity joints show increased motion during running.
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In the stance phase of running, the ankle contributes 60% of the power generation, whereas the knee and hip generate 40% and 20%, respectively.
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The knee is the principal shock absorber during running, absorbing twice as much energy as the ankle and hip.
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Abnormal biomechanics can lead to overload of other structures. Commonly, gluteus maximus weakness can lead to poor control of the lower limb and reaction forces being transmitted throughout the kinetic chain. As another example, an abnormal amount of rearfoot varus or pronation can abnormally load structures higher in kinetic chain, leading to increased valgus stress at the knee. This is an important etiological factor in patellofemoral dysfunction (see the Patellofemoral Dysfunction section later in the chapter).
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Orthotics may help prevent injury if significant biomechanical abnormalities are present. Screen with gait assessment during the preparticipation examination
Physiologic Issues
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Demands depend on type of activity
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Sprinters: Energy requirements provided primarily by anaerobic energy pathways. Glucose is the major fuel source.
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Long distance events: Energy requirements provided primarily by aerobic energy pathways, with fat and glucose derived from glycogen stores
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Middle distance and combination events : Combination of both aerobic and anaerobic pathways
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Specificity of training, including periodization, to demands based on type(s) of energy pathways used.
Strengthening and Conditioning
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Sport specificity in training is key in track and field. This differs for each event. Most training continues year round. There is a need to emphasize variability in training and avoid overtraining.
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Endurance and sprint athletes: The selective strengthening of certain muscle fiber types (fast-twitch vs. slow-twitch) demonstrates specificity (i.e., endurance-type training leads to changes in slow-twitch fiber morphology as well as enzyme metabolism specific for endurance-type activities). Similarly, explosive strengthening programs specifically train fast-twitch muscle fibers and the metabolic functions used to sustain these activities. It is more beneficial to train with sport specificity in mind when designing strength and conditioning programs.
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Use of the entire range of motion (ROM) for strengthening is important. Strength gains observed are specific to the range and speed at which strengthening exercises are performed.
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Field events: The successful transfer of ground reaction force through the foot, ankle, knee, hip, trunk, shoulder, elbow, wrist, hand, and finally, to the implement is critical to success in throwing events. Maintain quadriceps–hamstring balance. Again, sport specificity is helpful. A shoulder scapular stabilization and rotator cuff strengthening program will be helpful for the shot put, javelin, hammer, and discus. Reproduction of shoulder movement with manual resistance. Proprioceptive work is helpful in hurdles, discus, javelin, triple jump, and long jump.
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Develop smaller supporting muscles: Strengthening prevents development of medial tibial stress syndrome, plantar fasciitis, patellofemoral dysfunction, and other overuse injuries.
Flexibility
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Despite a lack of reliable data about the effects of increased flexibility in preventing injury, most agree that the introduction and usage of a flexibility program helps avoid acute muscle strains. If the muscle length at which maximal stretch felt is greater, it takes larger acute overload to “stretch” the muscle past this length, leading to injury. Flexibility remains an essential tool in the treatment of muscle strains and joint protection.
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A flexibility program should be worked into strengthening programs such that strength is improved throughout the ROM without loss of motion.
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Ballistic stretching should be avoided.
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Stretching should be performed after warming up, rather than while “cold” at the start of practice.
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Stretch larger muscle groups first, followed by smaller groups.
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Hamstring flexibility is important in mechanical low back injuries. If hamstring flexibility is limited, a posterior pelvic tilt is created and the trunk flexion becomes limited, increasing stress in the lower back.
Common Medical Problems
Preparticipation Physical Examination
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Stresses the importance of cardiac, musculoskeletal, and neurologic systems.
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Detailed family history is conducted, emphasizing any history of heart murmur, sudden cardiac death, Marfan syndrome, hypertrophic cardiomyopathy, or premature atherosclerotic disease.
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Screen for possible anatomic abnormalities that may predispose to injury; consider use of orthotics and a flexibility/strengthening program in the presence of muscle imbalances, especially of the hip abductors and gluteal musculature, assessed both statically and dynamically.
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Assess for nutritional or training errors, including any “self-restricted” food types. Inquire about lactose intolerance.
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Rule out significant medical or orthopedic problems that would preclude activity or require restrictions.
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In female athletes, pay special attention to menstrual dysfunction, hypocalcemic diets, a history of disordered eating, and/or a history of stress reactions or fractures (see the Female Athlete Triad section later in the chapter).
Nutrition Issues
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It is important to consider nutrition when an athlete presents with symptoms of fatigue, burnout, or recurrent minor injuries (see Chapter 5 : Sports Nutrition).
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Zinc, calcium, and iron are commonly deficient in athletes.
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Ideal nutritional intake: 6 to 13 g carbohydrates per kg body weight; 1.2 to 1.7 g protein per kg body weight; with the remainder of calories from fat. This translates into a diet of 60% to 70% carbohydrates, 10% to 15% protein, and 25% to 30% fat. No performance benefit has been shown with diets consisting of 15% fat versus diets consisting of 20% to 25% fat.
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If an athlete eats an adequate caloric intake from a variety of wholesome foods, nutritional needs are often met. Proper food selection, not supplementation, is the ideal form of nutrition.
Iron Deficiency
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Common in young athletes. Iron loss can be due to hemolysis with hemoglobinuria, gastrointestinal losses, and excessive sweating. Female athletes are at increased risk of anemia because of the additional loss that occurs with menses. Athletes are not immune from other medical problems, and thus a complete workup of an iron-deficient athlete is important.
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Iron deficiency or decreased iron stores can occur without anemia in as many as 24% to 47% of female athletes and 0% to 17% of male athletes.
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The dietary recommended intake varies based on sex and age. Females aged 19 to 50 years require 18 mg of iron per day, and males aged 19 to 50 years require 8 mg per day.
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Pseudoanemia: an increase in plasma volume of 6% to 25% with training results in hemoglobin and hematocrit appearing falsely low. Typically self-limited
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Screening for iron deficiency is recommended in elite athletes and high risk populations, such as vegetarian athletes, those with a history of iron deficiency, or athletes exhibiting an unexplained decrease in performance.
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Screening hemoglobin with a follow-up examination of ferritin is reasonable for assessing iron deficiency. Ferritin is a storage form of iron but can be transiently elevated in acute inflammation or following vigorous activity. Ferritin levels decrease, however, with longer term aerobic training. Iron and total iron binding capacity can differentiate pseudoanemia from true anemia.
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While anemia has been shown to affect athletic performance, the effect of iron deficiency alone is unclear.
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Supplementation of 325 mg ferrous gluconate twice daily is recommended if truly iron deficient. Increase intake of iron-rich foods and ensure adequate vitamin C intake.
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Calories
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While obtaining an adequate total caloric intake is obviously essential, this basic ingredient of good nutrition is often neglected.
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In an attempt to eat “healthy,” many athletes restrict fat intake. This strategy results in the risk of fat-soluble vitamins (vitamins A, D, E, and K) being deficient. Diets with less than 15% fat have shown no gains in athletic performance or health.
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Some athletes experiment by restricting calories as a means of reducing body weight, thus improving aesthetics and performance. This can increase the risk for developing a frank eating disorder, along with its concomitant medical problems.
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Other deficiencies found in athletes include zinc, magnesium, folate, as well as vitamins B6, C, and B12. Athletes should consider a nutritional consultation to formally review food intake if concerned about vitamin and/or caloric deficiencies.
Protein Intake
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Often an issue in vegetarian athletes and those that restrict food intake
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Consult a nutritionist to ensure adequate intake.
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If vegetarian, protein complementarity (with legumes and grains) can ensure adequate protein intake, but it is still important to assess iron intake. Minimizing this potential deficit may minimize potential fatigue and diet-related conditions.
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Voluntary protein intake, along with fat and total energy intake, has been shown to be lower in athletes with menstrual irregularities than in normally menstruating athletes.
Calcium
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Dietary reference intakes (DRI) vary based on age. The most recent guidelines suggest 1,300 mg daily for ages 14 to 18 years, and 1,000 mg daily for ages 18 to 50 ( Fig. 93.1 ).
Figure 93.1
Normal calcium and phosphate metabolism.
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Female athletes often consume less than the DRI for calcium.
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Calcium and estrogen are necessary in women for normal bone deposition. If depleted, this can lead to lower bone density. Peak bone density is reached in women in late teens to early 20s; thus, adequate intake in childhood and adolescence is critical.
Vitamin D
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Vitamin D is essential for bone health and the incorporation of calcium. Primary sources are sunlight and vitamin D–enriched foods such as milk.
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Vitamin D levels have been increasingly associated with generalized musculoskeletal pains.
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The DRI is 25 micrograms daily and vitamin D-25-OH levels can be monitored.
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Athletes who practice and compete in indoor sports and those living in Northern latitudes may be at risk . Consider supplementation if levels are low.
Nutritional Supplements and Ergogenic Aids
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Athletes are at risk for use and abuse of supplements, as well as ergogenic aids.
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Some of these are restricted under US Olympic Committee and NCAA drug testing. Examples include ingesting excess amino acids, medium-chain fatty acids, vitamins, minerals, herb extracts, special proteins, and enzyme complexes.
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Often marketed to individual sports
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There are reports suggesting that up to 62% of track athletes use supplements, including multivitamins.
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Specific questions related to pharmacokinetics, interaction with normal foodstuffs and prescribed medications, and side-effect profile should be asked of the pharmacist.
Supplements
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The positive effects of supplementation are unproven if the athlete is not actually deficient in a vitamin.
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In the setting of dehydration, amino acid supplementation may be detrimental if kidney function is marginal.
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Protein and vitamin supplementation in great excess can be dangerous.
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Excesses of most vitamins are eliminated from the body.
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Fat-soluble vitamins are stored within the body, and thus toxicity is possible.
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Most methods of supplementation are expensive.
Ergogenic Aids
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Erythropoietin, human growth hormone, and anabolic steroids
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Erythropoietin is detected by a urine test; new tests being developed to detect biosimilar formulations
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There is a blood assay to detect the use of human growth hormone.
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Anabolic steroids are detectable with urine drug testing.
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All are associated with significant side effects. Erythropoietin is associated with hyperviscosity syndrome and even death. Hyperviscosity syndrome is made worse with dehydration. Human growth hormone is associated with side effects that include acromegaly-like features and worsening of existing cardiovascular disease. Anabolic steroid side effects are well known.
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For up-to-date information, contact the US Anti-Doping Agency Drug Reference Line (800-233-0393).
Fluid Considerations
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During prolonged exercise, 2 to 4 pounds of body weight are lost per hour; equivalent to 1 to 2 L per hour.
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The rate of dehydration can be estimated by changes in nude body weight; each pound of weight lost equals 450 to 650 mL (16 to 24 ounces) of dehydration.
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Dehydration can incur physiologic changes: for every liter of water (2.2 pounds) lost while exercising in the heat, there is an increase in core body temperature of 0.3° C, increase in heart rate of 8 beats per minute, and decrease in cardiac output of 1 L per minute.
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Proper rehydration is essential before, during, after, and between events.
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Pre-exercise hydration should consist of 500 to 600 mL of water or sports drink 2 to 3 hours prior to exercise, and 200 to 300 mL 20 minutes prior to exercise.
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To maintain hydration, ingestion of 200 to 300 mL every 10 to 20 minutes is required to prevent greater than 2% body weight reduction.
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Postexercise hydration should aim to restore fluid loss accumulated during the event.
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Thirst is a delayed sensation and therefore is not a good indicator of hydration status.
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Water temperature does not affect body heat storage, and thus water should be consumed at a comfortable temperature (10°C–15°C) to promote hydration.
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Carbohydrates should be replaced if the exercise session lasts longer than 45 minutes or is high intensity.
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For an athlete who weighs 68 kg (150 pounds), the carbohydrate requirement is 30 to 60 g per hour. Carbohydrate and fluid needs can be met by drinking 625 to 1,250 mL per hour of beverages with 4% to 8% carbohydrate content.
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For a glycogen-depleted athlete, a postrace carbohydrate intake of 1.5 g per kg body weight during the first 30 minutes postrace, and again every 2 hours for 4 to 6 hours will effectively replenish glycogen stores.
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Some studies document a decrease in gastric emptying once the glucose concentration is above 6%. Water is still an excellent source for short distance events (<1 hour).
Nutritional Recommendations Are Different for Females and Males
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Societal influences have made constant dieting acceptable for girls and women, and athletes are even more likely to attempt to change body appearance if they think it will improve performance.
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Females at increased risk of nutritional deficiency, as well as eating disorders.
Female Athlete Triad
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Three interrelated conditions: low energy availability (with or without an eating disorder), menstrual dysfunction, and altered bone mineral density, each on a continuum from healthy to disease state. (see Chapter 12 : The Female Athlete; Chapter 27 : Eating Disorders in Athletes) ( Fig. 93.2 ).
Figure 93.2
Female athlete triad.
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Present in every sport, but most commonly seen in sports that select for a lean body weight (swimming, cross-country skiing, cross-country running) or in sports scored subjectively (gymnastics, figure skating, diving)
Low Energy Availability/Disordered Eating
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When energy availability falls below a threshold due to an imbalance in energy expenditure, cellular maintenance, growth, and reproduction are disrupted.
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Origins are multifactorial: genetics, perfectionism, personality traits, identity, self-esteem, family dynamics, coping skills, control issues, alterations of body image, and/or need for control. Patients often have a history of sexual or physical abuse. Societal pressures increase risk.
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Inadequate caloric intake can also result from lack of knowledge of proper nutrition.
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Prevalence estimates of disordered eating among high school and college athletes range from 15% to 62%, compared with 13% to 20% in the general adolescent female population.
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Characteristics associated with successful athletes that lead to overlapping and increased risk for developing eating disorders include perfectionism, goal setting, and overachieving.
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Subtle messages by coach, parents, or teammates (often unintentional) can add to pressures that lead an athlete to experiment with pathogenic weight control behaviors:
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Misconception that lower body weight improves performance
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Educating coaches in how to recognize and prevent eating disorders is essential.
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Difficult to identify; a team approach is often necessary for proper treatment
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The treatment team usually includes a physician, psychiatrist, and nutritionist. Additional support system includes coaches, sport psychologists, athletic trainers, and families. Psychological counseling is a cornerstone.
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Treatment usually not very successful, emphasizing the need for prevention through education and early identification.
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Screen for concomitant depression. Preliminary studies suggest a favorable response to antidepressants such as fluoxetine.
Menstrual Dysfunction
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Common in athletes, especially endurance athletes
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Menstrual dysfunction may include a shortened luteal phase, anovulation, oligomenorrhea, or amenorrhea.
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Strenuous training alone does not cause menstrual dysfunction; requires concurrent dietary restriction.
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Exercise-associated menstrual dysfunction remains a diagnosis of exclusion.
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The physician must rule out other conditions such as pregnancy, thyroid disorders, adrenal disorders, prolactin-secreting tumors, and/or ovarian disorders.
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Important to initiate workup and treatment because of the long-range consequences of menstrual dysfunction. Treatment must be individualized.
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“Progesterone challenge” helpful in functionally differentiating an estrogen-deficient state from an estrogen- and progesterone-deficient state.
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If exercise-associated amenorrhea is diagnosed and no contraindication exists, estrogen and progesterone supplementation should be considered. Many use age 16 as the younger cutoff for initiating treatment.
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The oral contraceptive pill has a good side-effect profile, is well tolerated, and has convenient packaging. If positive progesterone challenge, can use monthly progesterone alone
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Other considerations: decrease training intensity; increase body weight if underweight; assess nutritional intake; maintain high index of suspicion for eating disorders
Osteoporosis and Stress Fractures
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The bone is constantly remodeling; the process is a balance between osteoblast and osteoclast activity.
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Amenorrheic runners have lower estrogen levels and lower bone mineral density (BMD) than runners with normal menstrual cycles.
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An alteration in homeostasis due to low energy availability and low estrogen levels, which increases osteoclast activity, leads to decreased BMD.
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Stress fractures are caused by increased stress on normal bones (stress fractures), or normal stress on abnormal bones (insufficiency fractures) ( Fig. 93.3 ).
