The core is where the human body’s center of gravity is located and where all movement begins. Core stabilization is particularly important for an athlete to achieve optimal performance. Whether the individual is competing at the school-age or an elite level, the athlete may experience pain symptoms only with functional overloading, while the pain may be absent or not disabling in normal daily activity. Additionally, injuries in other regions of the body can occur primarily because of poor core stability. However, treatment of injury is also different for the athlete, for complete functional recovery needs to take place in as short a period of time as possible (1).

All athletes are subject to the repetitive axial compressive and torsional forces required in athletic competition (1,2). Other factors involved include injuries due to collisions, the quality of the playing surface, the athlete’s age and experience, and excessive physical demands of the sport (3). Many individuals have developed functional strength, power, neuromuscular control, and muscular endurance; however, few people develop the muscles required for spinal stabilization. Even with their peak conditioning, superior motor skills, and higher motivation, elite athletes have not only about the same incidence of back pain as the nonathlete population, but also have the same problems with activation of stabilizing muscles of the trunk (4). Athletes who train in one particular sport frequently, or who compete year-round without rest, may experience overtraining syndrome due to lack of definition of an optimal training zone and the limited ability of bone and connective tissue to quickly respond to match the demands of the sport. This has led routinely to arm, shoulder, and lumbar instability, chronic nonsteroidal anti-inflammatory (NSAID) use, and time loss injuries during the season (3).

The athlete’s core is composed of the trunk, and the pelvic and shoulder girdles. The core operates as an integrated functional unit enabling the entire kinetic chain to work synergistically to reduce force load, dynamically stabilize, and generate force against abnormal forces. An efficient core allows for the maintenance of optimal length-tension relationships of functional agonists and antagonists, which makes it possible for the body to maintain optimum force-couple relationships.

All functional activities are multiplanar and require deceleration, dynamic stabilization, and acceleration. Movement may appear to be single plane dominant, but the other planes need to be dynamically stabilized to allow for optimum neuromuscular efficiency (1). Optimal articular range of motion, muscle strength and extensibility, stability, and the best automatic movement patterns possible must be present in these areas (5).

The trunk muscles must be able to hold the vertebral column in a stable position in order for independent upper and lower extremity movement to occur and to enable load to be transferred from the upper extremity to the ground. If extremity muscles are strong and the core is
weak, there will not be enough force created to produce efficient movements. A weak core is a fundamental problem inherent to inefficient movement that leads to predictable patterns of injury. The core musculature is an integral part of the protective mechanism that relieves the spine of the excessive forces during competition.

Athletes who participate in high-impact sports that require great physical strength need strong core musculature in order to generate sufficient force to play their position safely and absorb the impact of collisions. Football players and hockey players must be able to generate force quickly, while being able to perform highly coordinated movements. This is not possible without a strong base musculature, trained in a sport-specific manner. Throwing or racquet athletes require strength and neuromuscular coordination throughout their trunk, pelvic and shoulder girdles, and lower extremities to generate the needed force from their proximal to distal upper extremity. Golfers generate most of their power though the trunk and pelvic girdle, even though the successful golf swing is mediated through the upper extremities (2).

The core maintains postural alignment and dynamic postural equilibrium during functional activities, and relies on an efficient neuromuscular system. If the neuromuscular system is not efficient, it will be unable to respond to the demands placed on it during athletic endeavors. A strong and stable core can improve optimum neuromuscular efficiency by improving dynamic postural control. As the efficiency of the neuromuscular system decreases, the ability of the kinetic chain to maintain appropriate forces and dynamic stabilization decreases significantly. Decreased neuromuscular efficiency leads to compensation and substitution patterns, as well as poor posture during functional activities. These altered patterns lead to increased mechanical stress on the contractile and noncontractile tissue, and lead to repetitive microtrauma, abnormal biomechanics, and injury. Research has demonstrated that people with low back pain have an abnormal neuromotor response of the trunk stabilizers accompanying limb movement, as well as greater postural sway and decreased limits of stability (1).

Decreased dynamic postural stability in the proximal stabilizers has been demonstrated in individuals who have sustained lower extremity ligamentous injuries. It has also been demonstrated that joint and ligamentous injury can lead to decreased muscle activity. Articular or ligamentous injury can lead to joint effusion, which causes pain, which in turn leads to muscle inhibition and altered proprioception and kinesthesia. The result is altered neuromuscular control in other segments of the kinetic chain, destabilizing them and breaking down the kinetic chain (3).

The neuromuscular system must be able to stabilize the spine against shear in all directions (i.e., torque, traction, and compression) if the trunk is to remain stable during repetitive or forceful activities and be able to absorb the impact of collisions. Stability is dependent on three systems (4,5):

Bergmark classified the lumbar muscles as either local or global, while Lee refers to these muscles as the inner unit and the outer unit (5,7,8).