By Dr. Gretchen D. Oliver, FACSM, ATC, Director of Sport Biomechanics Group, University of Arkansas
Over the past few decades there has been an increase in injury to youth participating in sport. The issue of youth sport injury has become a conundrum because if there is an increase in injury, then subsequently there is usually an increase in participation. With the insurgence of childhood obesity, youth participation in sporting activities has been encouraged.It has been proven that regularly scheduled physical activity is associated with health improvements and reduced incidence of disease. There has been an increased awareness for the need for daily physical activity in attempt to combat the epidemic of childhood obesity. In addition to battling the obesity rate, physical activity has beneficial effects on the physical and mental health of youth. Established patterns of behavior are acquired at an early age thus reiterating the importance of youth being physically active. If a child is physically active at a younger age, he/she tends to develop a healthy behavior pattern. The recommendation from the Centers for Disease Control is for children aged six and older to participate in moderate to vigorous physical activity throughout their lifespan. Many children accomplish this by participating in sports. While this choice of physical activity certainly meets the recommended standards and affords children the opportunity to experience and maintain so many health and wellness benefits, the physical demands of the sport and the proper body mechanics to perform the sport daily must be addressed. Repetitive overuse issues are common in youth physical activities; in addition injury prevalence increases as the overuse activity increases.
It has been reported that yearly the US averages 20 to 30 million youths between the ages of 5 and 17 participate in some form of community sponsored sports program. 1,2,3Much focus has been on the prevention of youth sports injuries that are disabling their chance to live out their life dreams of athletic greatness later in life. Researchers have explored the benefits of youth sport involvement for many years. Well-organized programs can have a direct positive impact in participants’ skill development, physical fitness, competitiveness and social development. During the sampling years [6-12] of youth sport involvement, children are exposed to various sports for short amounts of time that utilizes different skills, mechanics and rules. Once a child finds her/his specialization [between ages 13-15] the focus on one sport takes precedence over others, and many times the child concentrates on that particular sport and often begins playing it year-round.
Of one subgroup of youth sport injuries are those that occur to youth baseball and softball players. In 2010, Little League Around the World reported 2,168,850 baseball participants and 344,910 softball youth participants4. As previously stated, it is common for youth to participate in sport year-round with sport specialization becoming customary. With the increase in participation and specialization, also comes the risk of injury. Over a two year period, 128 injuries were reported by 534 seven to thirteen year-olds participating in baseball 5.In high school individuals, for every 100 baseball and softball players, an injury rate of 13.2 was sustained within a three year span.6 In a survey of 300 youth throwers reporting on a year of throwing, more than half reported of having some form of shoulder and elbow pain7, while over 500 pitchers aged 9-14, 50% reported of some type of shoulder or elbow pain throughout the season8. Based on epidemiological studies, it is evident that youth and adolescent throwing injuries are on the rise.It has been vastly documented that shoulder and elbow pain in youth throwers has become an epidemic 7,9-11.
With the increase in participation rates in youth baseball and softball there is a colossal concern for potential injury exposure these children are experiencing. The injuries incurred by this population of boys and girls participating in baseball and softball are primarily overuse in nature. Most youth injuries occur from improper mechanics.
Previous research has examined the gluteal muscle group and its relationship with pelvic and trunk movement12 during youth baseball pitching. Baseball pitching involves an overhand throwing motion that is utilized by all baseball and softball positional players. Previous research13has revealed a positive relationship between rate of axial pelvis rotation and preferred leg gluteus maximus activity at shoulder maximal external rotation [also known as the cocking phase of throwing] and ball release. It has been shown that the greater activation of the gluteus maximus on the preferred or drive leg revealing that it was active in externally rotating the hip throughout the event of maximum shoulder external rotation through ball release. Thus based on the kinetic chain principle, this increased activation may result in increased rate of pelvis axial rotation throughout throwing cycle. In addition it was found that the non preferred gluteus medius not only acts to stabilize the pelvis but also allows for increased hip internal rotation throughout shoulder maximum external rotation on to ball release.To further examine the hips as a part of the kinetic chain and injury predictor, it has been revealed that the pelvis and torso direct the function of the shoulder during the overhand throwing motion.13 It has been documented that the rate of axial torso rotation, as a result of gluteal activation, is the driving component of shoulder motion. Therefore, it can be concluded that gluteal and hip motion are a direct link to shoulder motion when throwing overhand.12,13
When discussing injury mechanics and prevention in youth, focus should be on the total body no matter the sport. Youth injury prevention should begin with assessing postural control. Dynamic human movement requires the entire body to work together as linked segments. Typically youth lack torso or core stability that often results in injuries to the more proximal joints such as the shoulder or elbow due to compensatory mechanisms. Torso or core stability involves the musculature of the lumbopelvic-hip complex. Having torso or core stability allows for efficient energy transfer from the lower extremity to the upper extremity. This energy transfer is needed for any type of dynamic movement. By having efficient energy transfer youth are about to utilize greater energy and have less potential of injury to the weaker links. Example, the shoulder is not designed to produce force; it is designed to transfer the force. Thus in attempt to protect the shoulder in overhead movements energy generated from the lower extremity [or more proximal segments] should be efficiently transferred through the shoulder and out to the hand [more distal segment]. If there is not efficient transfer of energy then the shoulder is culprit of trying to become a force producer and over time will become injured.
In attempt to obtain postural control, youth should begin with an initial postural assessment. Having youth ‘stand up straight’ encouraging to pulling in the belly button and stand at attention. Standing up straight allows them in pelvic neutral and if they are maintaining pelvic neutral then they are working on core stability. Other effective means of injury prevention are body weight body awareness exercises such as those presented in the following link http://hhpr.uark.edu/biomechanics/KINS/core__youth_ATSHC.pdf
Children and adolescents are resilient and if pain becomes present then the origin of that pain needs to be identified so that further pain and/or injury can be prevented. Being proactive and having proper assessment of the problem or more importantly, preventing an injury with appropriate assessment and body weight awareness exercises will increase the likelihood of proper development of skill and fitness of youth athletes assuring lifelong involvement in physical activity.
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13. Oliver GD, and Keeley DW. Pelvic and trunk kinematics and their relationship to shoulder kinematics in high school baseball pitchers.Journal of Strength and Conditioning Research, 2010;24(12): 3241-3246.