The “Core”: Preventing Injury and Improving Sports Performance in the Overhead Throwing Athlete

By Dr. John R. Mishock

Major League Baseball (MLB), injuries cause an estimated half-billion dollars in lost revenues annually. (MLB injury stats, 2019) Arm injuries account for > 50% of all MLB injuries, equating to 460,432 days on the MLB disabled list, with the numbers continuing to rise. (Conte S. Am J Ortho 2018) At the youth and adolescent level, baseball injuries are a significant problem, with more the 110,000 children under age 18 years of age being treated by health care providers. The majority of these injuries are soft tissue related injuries of the shoulder and elbow. (Lawson. Pediatrics. 2019). Repetitive throwing leads to microtrauma to the soft tissues of the shoulder and elbow. With inadequate rest and recovery, inefficient throwing mechanics, and poor arm and body care fitness, injury ensues. The high-level athlete of today must not only have the ability, but they must have durability. Durability can be created through a scientifically based training program that not only prevents injury but improves sports performance. A recent study demonstrated this by showing that a scientifically based exercise training program could reduce greater than 50% of all sports-related injuries. (Sakata. Am J Sports Med. 2019). This article will focus on “Core” (spine, pelvis, and hips) weakness and poor motor control and its implication in baseball-related throwing injuries.

The “Core” (corset or hoop-like action) is a series of 29 muscles of the trunk, pelvis, and hips involved in movement and body stability. Core stability refers to the body’s ability to control the trunk’s position and motion (proprioception) while the arms and legs are moving. Core stability happens through a muscular contraction (strength, endurance, and motor control), creating a compression of the spine, pelvis, and limb joints. To have stability in the limbs, the individual must first have stability in the “core.”

Optimal core stability allows the limbs to move with greater freedom, control, and efficiency, thus preventing aberrant movements that can facilitate injury. Core stability also allows optimal force to be transferred from the ground or through various body segments, enabling the development of power (force x velocity) to enhance sports performance. With adequate core stability, the athlete has a strong base to generate force and explosiveness in throwing hard, hitting far, running fast, and jumping high.

The connection between sports performance, arm injuries, and inadequate “core” stability is becoming more apparent in the scientific literature. A decrease in the “core” force during pitching by 20% can increase the shoulder and elbow complex load by 34%. (Litner.Clin Sports Med. 2008) In other words, a weak core causes the arm to work harder. This increased work load by the arm can lead to poor performance and injury. In a study of 347 professional baseball players, poor core stability led to a four times greater likelihood of missing 30 days of playing time due to injury. (Chaudahri. Am j Sports Med. 2014)

Tommy John ligament injuries (elbow medial collateral ligament tears) are becoming epidemic in baseball players, with the fastest-growing segment happening in baseball players 15-18 years of age. Poor core stability increases the likelihood of this type of injury. In a study of 30 male baseball players with “Tommy John ligament” tears, all had poor strength and motor control of the “core”. The authors concluded that the deficiency of core strength and motor control leads to the early opening of the hips and pelvis during pitching, causing increased biomechanical force at the elbow. (Garrison et al., 2013)

In some cases, a previous “core” injury can lead to arm injuries. In a study of 247 Major league Baseball players who underwent Tommy John Surgery, 30% of them had endured an abdominal, hip, groin, or proximal hamstring injury. It was theorized that an inadequately rehabilitated core led to altered pitching mechanics leading to elbow strain and injury. (Kantrowitx. Orthop j Sports Med. 2018).
How does poor core stability lead to arm injuries?
After repeated throwing, the “core” fatigues leading to decreased control (proprioception) of the shoulder and arm joints (scapulothoracic, glenohumeral, elbow, and wrist joints). This unstable base leads to compensation and altered throwing mechanics (trunk rotation to occur before front-foot contact, increasing shoulder and elbow stress) (Aguinaldo, 2009, 2007).
During core fatigue, stress on the shoulder increased by 56 lbs., causing the arm bone (humerus) to drive into the shoulder joint (acromial arch). This mechanical change leads to a shoulder injury (subacromial and posterior impingement and glenoid labrum tears). (Trip et al. 2017) This biomechanical strain can lead to a 49% increase in shoulder labral injury (capsular cartilage providing stability for the shoulder joint). (Burkart et. al.2015)

At the elbow, the core fatigue causes 67 lbs of shear force, putting the Tommy John Ligament at significant risk. The fatigue also affects pitch control by changing the release point leading to low pitch accuracy. When a pitcher loses control, this can be the first significant indicator for the coach to visit the mound and potentially remove the player from the game. Interestingly, in this study, fatigue occurred between 34 and 90 pitches in these college baseball players. (Tripp et al. J Athl Train.2007) How often do you see youth and adolescent pitchers throwing much more than 34-90 pitches? Not only do they throw more than this, they often pitch with poor throwing mechanics and physically immature bodies. Are we putting our kids at risk?

Can a core training program increase pitch velocity and accuracy?
Having good “core” strength, endurance, and motor control has been shown to significantly impact throwing velocity, throwing distance, and overall sports performance. (Cope T et al. Phys Therapy.2019) In baseball players, 50% of throwing velocity occurs due to torque created by the core. Only 15% comes from the throwing arm and the rest from the lower half (legs) at a push-off. (Kibler et al. 1995)

Studies show, that the appropriate core training program can increase throwing velocity by up to 5% (Manchado et al. J Athl Train. 2015) (Palmer T. Et al. J Athl Train.) (Palmer T. et al. J Athl Train. 2015), while reducing elbow and shoulder injury incidence by 40%. (Laudner et al, 2019)
Not only does a core training program prevent injury and increase throwing velocity it also improves baseball pitch control. Research has shown that core stability training improved throwing accuracy by 6.1% after 6 weeks of exercise training in youth and adolescent baseball players. (Lust et al. J Sport Rehabil. 2009).
How does the stability of the core improve pitch velocity and accuracy?

Increasing stability of the “core’ improves base of support allowing increased mobility and force pattern generation of the arm. This occurs by recruiting the most important muscle groups at the right time while turning off those muscle groups that are not needed (neurological recruitment and inhibitory reflex patterns). Further, it helps stack the force generated from the ground (ground reaction force) at push-off, transferring the energy up the kinetic chain (link of moveable body parts) sequentially through the lower half, core, shoulder, arm, and hand, leading to the baseball’s explosive release. The stability also increases accuracy by allowing for a more consistent ball release point. (Sharon RS et al. J Appl Physiol. 1994).

The evidence clearly shows that the proper core training program can optimize sports performance and prevent injury. Now is the time to start your arm care and core training program as part of an off season training routine.

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Dr. Mishock is one of only a few clinicians with doctorate level degrees in both physical therapy and chiropractic in the state of Pennsylvania. He has also authored two books; “Fundamental Training Principles: Essential Knowledge for Building the Elite Athlete”, “ The Rubber Arm; Using Science to Increase Pitch Control, Improve Velocity, and Prevent Elbow and Shoulder Injury” both can be bought on Amazon.

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