Throwing a baseball requires coordination between multiple muscles and surrounding joints within the body. The art of throwing is so specific and detailed that any altered kinematics leads to injury predisposition.
There are major differences in throwing kinematics between the different baseball positions. Catchers, versus pitchers, use a shorter stride length with minimal pelvis-trunk rotation that results in low humeral elevation with minimal forward trunk tilt (1). Compared to other positions catchers throwing mechanics is less efficient because of their quick release. Regardless of this movement inefficiency general commonalities still apply. Lumbopelvic-hip complex (LBPHC) stability and strength may be the most important component of throwing; without pelvic and trunk stability athletes are more susceptible to injury, particularly in the shoulders.
LBPHC is made up of the spine, hips and pelvis, proximal lower limbs and abdominals. LBPHC stability during throwing, which is when trunk posture is maintained, prevents postural collapses and altered kinematics. An inability to stabilize the lower extremities and LBPHC predisposes athletes to injury pathomechanics.
The core plays a critical role in all athletic movements. During throwing the core maintains stability of the pelvis and spine while transferring energy from large to small segments, which requires coordinated sequencing. Pelvis and trunk maintain pelvic stability while aiding in energy transfer from the lower to upper extremities (2). During throwing, energy, which we will refer to as power, is initially generated from the lower extremities, transferred through the core and then released with the ball through the shoulder, elbow, wrist and hand. The gluteus muscle group maintains pelvis and trunk position to allow for efficient kinematics.
The glutes are highly active during foot contact and are primarily responsible for stabilizing the entire LBPHC. Without stabilization throwing kinematics are off, which alters the entire kinetic chain (2). The glute medius stabilizes the pelvis and torso during single leg balance movements (i.e. pitchers front leg during the throwing action); it also acts as a hip internal rotator and pelvis stabilizer, which allows pitchers to control the pelvis axial rotation rate (3). The glute maximus is primarily responsible for generating power during forward leg movements (i.e. the drive leg during throwing).
The difference between the gluteus medius and maximus is immense. The gluteus medius, as aforementioned, is primarily responsible for the stabilization of the LBPHC. More specifically, it is a lateral stabilizer during open chain stepping and a pelvis leveler during closed chain weight transfer. Closed chain is when the foot is planted on the ground and open chain is when the foot is off the ground. The gluteus maximus externally rotates and extends the hip. During throwing, the stride leg gluteus medius is active throughout the entire throwing motion
Studies have shown premature trunk rotation as a common kinematic alteration in youth pitchers, which results in excessive horizontal abduction of the shoulder (4). This inefficient movement alteration increases upper extremity force and predisposes baseball players to shoulder injuries. This study supports the theory that lack of development within the posterior chain in both young and adult athletes is a major issue. The inability to activate the gluteus muscle group efficiently should be stressed more during all levels of training.
The gluteal muscle group is critical and highly active during throwing. The drive leg uses the gluteal muscle group to generate power to push the thrower towards their target. The stride leg uses the gluteal muscle group to stabilize and allow for single leg support. Inefficiency in either of these actions leads to altered kinematics and predisposes athletes to injuries, especially in the shoulders. A strength program that emphasizes LBPHC stability is a must in young and adult athletes. Compound multi-joint movements such as full squats, Bulgarian squats and/or Olympic lifts are the best exercises to strengthen the LBPHC and core. Isometric exercises such as single leg bridges, reverse bridges, clams and various others specifically target the posterior chain (i.e. glutes). These exercises, along with biomechanically specific dynamic movements, can not only drastically increase the accuracy and power of the throw but they can prevent injury.
The best time to get athletes started on a training program is while they are growing up. Proper training programs have proven highly successful in creating efficient mechanics; decreased risk of injury; neuromuscular adaptations; total body coordination; and overall athletic performance. Results have shown for athletes as young as five and six years old. With the information at hand, with injuries lurking at each corner and with the desire to perform I pose this question… “Why wait until it is too late?”
SOURCES
1. Plummer, HA, Oliver, GD. The Relationship between Gluteal Muscle Activation and Throwing Kinematics in Baseball and Softball Catchers. J Strength Cond Res 28: 87-96, 2014.
2. Kibler, WB, Press, J, and Sciascia, A. The Role of Core Stability in Athletic Function. Sports Med 36: 189-198, 2006.
3. Oliver, GD and Keeley, DW. Gluteal Muscle Group Activation and its relationship with Pelvis and Torso Kinematics in high-school Baseball Pitchers. J Strength and Cond Res 24: 3015 – 3022, 2010.
4. Keeley, DW, Hackett, T, Keirns, M, Sabick, MB, and Torry, MR. A Biomechaincal Analysis of Youth Pitching Mechanics. Pediatr Ortho 28: 452-459, 2008.