The Physical Activity of Children Today

The physical activity of children today is much different than it was even 30 years ago. Then, children had physical chores, free play and back yard games. Today, children are in organized and structured activities. Large numbers of children are involved with traditional school based sport programs and athletic travel teams as well as club programs, summer camps and personal training programs. It is estimated that 30 million children, ages 5 to 17 years, are involved in organized athletic programs. This involvement has created an environment in which many youngsters train and compete on a year round basis, often in a single sport.It is estimated that approximately 33% of children involved in sports will be treated by a doctor or nurse for a sport related injury. Approximately, 50% of these injuries will be attributed to overuse injuries.

There are a number of reasons for youth sport injuries. Research has identified the following as frequent mechanisms for sport injuries15 :Inadequate pre-participation physical examsPoor fitness levels of childrenGrouping teams by age instead of sizeSport specialization at an early ageLack of coaching educationConditioning and training errorsPlaying through fatigueGrowth Inadequate pre-participation physicals are a concern in youth sports. Children need more than a basic physical before they participate in sports. The pre-participation physical is an opportunity to prevent an injury. This is the time to determine if the youth has any physical conditions that may predispose him to injury or musculoskeletal problems that could be improved with rehabilitation. For instance, Wang et al.(All et al. should be in italics) showed that postural sway can be a valid screening tool for basketball. This study showed that high school athletes who showed a high variation of postural sway were at greater risk for ankle injuries. If a child displayed postural sway during a sports physical then the doctor could recommend balance training before basketball season.

Another risk factor may be inadequate physical conditioning. In a recent editorial in the British Journal of Sports Medicine, Stovitz et al. wonders if we are “overusing the term overuse.” He thinks people are being scared away from physical activity in order to avoid overuse injuries. His contention is that people are being injured because of the “underuse” of their bodies. They are not physically fit. Fewer athletes are exposed to a basic physical education program and many spend an enormous amount of time in front of a television or computer. Due to this lack of education and inactivity many athletes are not prepared to meet the demands of a sports program. Heidt et al. found that a pre-season conditioning program contributed to a decrease in sport injury. Forty-two out of 300 female soccer players were randomly chosen to participate in a 20 session pre-season training program customized to their sport and position. The most significant finding in this study was that in the untrained group, injuries were significantly higher than in the trained group, (33.7% versus 14.3%, respectively).

The focus of many youth programs is on the development of sport specific skills rather than on the development of fundamental fitness.6 If the coach’s primary focus is on winning, time may be spent on developing the skills of their players to the neglect of the overall fitness of the athlete. Olsen et al. upon questioning 140 pitchers, found that 50% of all the pitchers perceived their coaches to be more concerned with winning the game than about the pitcher’s health. Emphasis on sport skills over fundamental fitness may lead to overuse injuries.6 Smith et al.20 speculated that overuse injuries sustained by young athletes could be reduced by as much as 50% if more emphasis was on fundamental fitness before sports participation. After the beginning of puberty, grouping kids by age could be problematic.12 In 2005, a Little League World Series player from the All-Star team of Dhahran, was 6’ 5” tall and weighed 226 pounds. The average weight of a Little League player is 111 pounds.4 This is quite a disparity and cause for concern. Matching of athletes’ weight and physical maturity may be important in decreasing physical injury.

Children should be encouraged to play a variety of sports while growing up to develop a foundation of physical fitness. Specialization before the age of 10 could lead to overuse injury.6 Many parents have encouraged specialization in a sport at an early age in hopes of the child winning a college scholarship or becoming a professional athlete. By playing one sport year round the body is not given rest and recovery time, and could potentially lead to an overuse injury. Explain why, mechanically. Children should be allowed to experiment with different activities to develop skills and interests in addition to general fitness. The United States is the only country in the major sporting world that does not have a national coaching education program. There are no federal laws requiring coaching education at any level of competition. Although the enthusiasm of volunteer and paid coaches is appreciated and welcome, untrained coaches could unknowingly contribute to the occurrence of sport injury. Many coaches of youth sports are largely uninformed about the growth and development of children and proper conditioning and training techniques.

The National Association for Sports and Physical Education (NASPE) has developed the National Standards for Athletic Coaches. It is a core body of knowledge that coaches should know. It is 37 standards including information on basic first aid and CPR, growth and development of children, training and conditioning and risk management.16 Playing through fatigue and pain is another causative factor for injury. In a 2003 study, it was shown that injuries increased when training loads increased significantly.1 A majority of the injuries occurred when the athlete’s body was fatigued, as in near the end of a practice session.1 It is important that the coach (or parent) does not push the child too fast. There should be no more than a 10% increase each week in the amount of distance covered, amount of training time added or the number of repetitions performed in an activity. This goes back to proper training for the coaches. Acute growth plate injuries may account for as much as 30% of sport injuries. A child is most vulnerable to injury during a growth spurt. The physes may be 2-3 times weaker than the surrounding fibrous tissue. Therefore, growth plates frequently yield before failure of surrounding ligaments or bone.10 A force that in an adult might cause a sprain could lead to a serious growth plate injury for an adolescent.

The growing parts of the bone include the physes and the epiphyses. Two types of epiphyses found in the long bones of children and adolescents are pressure and traction epiphyses.2 Pressure epiphyses are found at the ends of long bones and are subject to compressive forces. The epiphysis of the distal humerus, is an example of a pressure epiphysis. Injuries to pressure epiphyses may result in growth disturbances. Traction epiphyses or apophyses are located at the site of tendon attachment for a major muscle. An example is the apophysis of the tibia tubercle. The apophyses are subjected to tensile forces. They contribute to bone shape but not longitudinal growth. If an apophyses site is injured it will cause great discomfort but it will not disrupt longitudinal bone growth. An example of an overuse apophyseal condition is medial epicondylopathy in the throwing arm2, commonly known as Little League Elbow. The elbow is the most common injury site in young baseball players. Overuse injuries such as a traction apophysitis may occur in a young athlete when the growth center is unable to meet the demands placed on it during an activity.

Basic elbow anatomy and kinematics The elbow is a complex joint that is extremely important in the kinematics and kinetics of pitching. It is a two degree of freedom joint: flexion and extension and pronation and supination. The range of motion is 140◦ to 145◦ and 120◦ to 140◦, respectively. The elbow has a valgus angle, called the carrying angle, of about 10◦ to 15◦, although womens’ carrying angles tend to be somewhat greater. Stability of the elbow is accomplished by the congruency of the bony structures, the extensive joint capsule and four surrounding ligaments. The primary tensile stresses of the elbow are sustained on the medial side, especially in throwing. The medial collateral ligament is the primary stabilizer against valgus stress.

Biomechanics of throwing. The six phases of throwing: wind-up, stride, arm cocking, arm acceleration, arm deceleration, and follow-through. Images represent the instances separating the phases: initial motion, balance point, foot contact, maximum shoulder external rotation (MaxER), release, maximum shoulder internal rotation (MaxIR), and fielding position. The six stages of throwing are the wind-up, stride, arm cocking, arm acceleration, arm deceleration, and follow through. The point of maximum shoulder external rotation is at the beginning of the arm acceleration. The point of maximum shoulder internal rotation is at the beginning of the follow-through. Coordination of all six stages is important in order to prevent overload and overuse injuries. In the windup stage the forearm is slightly pronated and the elbow is flexed. In the stride the elbow is extended slightly. In late cocking the forearm is fully pronated, extended to 90◦, and the shoulder is cocked into external rotation. Up to this point the forces at the elbow have been insignificant but in late cocking the valgus forces begin and increase exponentially during acceleration resulting in loads that approach the ultimate failure point of the medial collateral ligament.

During acceleration up to ball release the elbow extends from 90◦ - 110◦ of flexion to 20◦ - 35◦ of extension. In late cocking the energy from the forward stride and the rotation of the pelvis and upper torso are transferred to the upper extremity.10 In professional pitchers the hand can move over 100 miles per hour10 while in top pitchers in Little League the hand can move 70 to 80 miles per hour.4 This motion has been described as the fastest in all sports.4 Fleisig et al. performed a kinematic and kinetic study to compare pitching mechanics of 231 male baseball pitchers (23 youth, 33 high school, 115 college, and 60 professional level athletes). They found that the biomechanics of pitching were remarkably similar, across all ages, except for the velocity parameters, which increased as the athlete’s strength increased and body matured. Although the stages of pitching are the same, it is not possible for the immature thrower to develop the same levels of force and torque that is seen in the mature adult because their arms are shorter and not as strong. Lower muscle mass, shorter moment arm, and reduced strength, as well as lower pitch counts contribute to the lower injury rate seen in young throwers compared to adults. This explains why injuries are less common in the 8 to 11 year old throwers.

For the reasons listed above, 12 to14 year old pitchers should also be protected from injury but they are actually the most common age group to develop overuse injuries to the elbow. This susceptibility to injury is because the peak growth rate of adolescents tends to occur during the ages of 12 to 14 years.8,10 Imagine that a child’s leg grows 2 inches during a growth spurt. The muscle and tendon of the limb lengthen during this time but do not hypertrophy until some time later, but because the limb mass and moment of inertia has increased the child will need to produce a maximum effort in order to produce movements similar to those performed before the growth spurt. This increased muscle force will cause the tendon to experience increased stresses.8 A growth spurt may result in changes in the ratios of muscle strength in relation to the length of the limb. Usually, muscle strength increases to match changes in the limb length although the tendons may be slow to adapt, putting the apophyses at risk for injury. Elbow pain is associated with many factors including, age, weight, height, number of pitches per appearance and season, satisfaction with performance, lifting weights, pitching while fatigued, warming up before an appearance and playing outside the league. However, the major contributors to elbow pain in youth baseball are thought to be pitch types, pitch counts and pitch mechanics. Throwing a curve ball or a slider places significant loads on the elbows and shoulders of adolescent pitchers.

The dangers of these loads are magnified for the adolescent athlete because their growth plates are still open and are more susceptible to injury.10 Lyman et al. followed 476 adolescent pitchers for one season and found that more than 50% threw a curve ball while only 14% threw a slider. They found a significant relationship to elbow pain when throwing a slider, especially for the 13 to 14 year old pitcher. There was a 52% increased risk of shoulder pain when throwing a curve ball. The change-up was the safest pitch for these adolescents with a 12% reduction of pain when throwing a change-up pitch.13 There have been many recommendations for limiting pitch counts in youth baseball. Lyman et al.13 found a 35% increased risk of elbow pain when a pitcher threw 75-99 pitches per game. They found that in 20% of the appearances more than 75 pitches were thrown. This high pitch count could lead to arm fatigue which has been found to be a major risk factor for overuse injuries in young pitchers. Shoulder and elbow pain in the young pitcher is a warning sign of an overuse injury.

Muscle soreness is normal, joint pain is not.13 Recommendations for preventing injury are to limit pitches in an appearance to 75 or under. In addition, a pitcher should not throw a curve ball or a slider until after 14 years of age. A young pitcher needs to develop proper pitching mechanics as early as possible and until that time should not be allowed to pitch as hard as they are able. Poor coordination or weakness at the beginning of the pitch will be amplified by the end of the pitch.10 It is interesting to note that no Little League All-Star pitcher has become a professional pitcher.10 In 2005, the National Athletic Trainers’ Association began a public-service campaign to educate young athletes and their parents. The campaign includes a poster featuring a winning team celebrating after a game, with this caption: “What will they have longer, their trophies or their injuries?”