Regardless of whether it involves opposing limbs of equal size and length, or balanced strength between both sides of the body (right vs. left and front vs. back), symmetry is nature’s preferred state. Lack of symmetry has been shown to impede physical development, increase the risk of injury, reduce performance, promote muscular weakness and increase the risk of injury. In resistance training, symmetry is a balance of muscle mass between both sides of the body, while proportion denotes the development of each muscle group, front-to-back and side-to-side.
Symmetry is important to baseball because of the repetitive nature of the game and the volume of work performed during the season. At the Major League level, teams play 162 games during the regular season. With spring training and possible post-season play, major leaguers participate in approximately 203 games in 220 days, and that’s only through the first round of the play-offs. Minor League players participate in 142 regular season games in approximately 160 days. Professional baseball is a grind.
At the Major League level volume overload is one of the leading causes of injury, and symmetry becomes extremely important when efficiency is disrupted. It has been said that “movement begins and ends with posture”, and this is especially true in baseball. Posture is important regardless of whether you are involved in the game, sitting in the dugout or bull pen, traveling in a car, cab, bus or plane, sitting at a locker or playing a video game at home or in a hotel room. Asymmetry can lead to inefficiency; inefficiency can lead to overload and overload can lead to breakdown. When a joint lacks appropriate motion to create and dissipate force, synergistic structures in and around the joint are forced to assist and/or compensate for the lack of motion. With proper alignment and symmetry in involved structures the cumulative effects of volume overload are minimized because each muscle can function properly and not have to assist or compensate for another muscle or group of muscles. When joints line up properly, there is less wear and tear on the body.
Symmetry in a Side-Dominant Sport– Often there is side dominance in baseball; i.e., most players will hit and throw from only one side. If a player hits and throws from the right side, e.g., they may exhibit a baseball specific adaptation of increased in internal rotation in the left hip and an increase in external rotation in the right shoulder. These two adaptations often accompany each other. Sport-specific adaptation is an interesting debate topic. Are these adaptations the reason why an athlete excels, or has his body adapted for preservation? Regardless of which side of the fence you are on, the next topic to be debated is; would an athlete with perfect posture and symmetry ever suffer a non-contact injury? Another interesting question is what should you do with an athlete with who demonstrates asymmetrical movement? Are corrective exercises necessary, or will pressing or squatting as much as possible fix the problem? There may not be a definitive answer, but anecdotally we have found that asymmetry and poor posture can lead to injury and injury is not good.
Every sport has specific adaptation patterns and baseball is no different. Not all adaptations are addressed immediately due to the risk of unnecessary motor engram reprogramming. A practical example of this would be implementing a corrective program for a player that has bad posture that causes him to lose 3 MPH on his fastball. Sometimes it’s necessary to let sleeping dogs lie because it’s impossible to make everything perfect. A good practitioner will use his/her experience to sift through the pros and cons and make the right call.
Over the years with the Diamondbacks the sports medicine team has observed that faulty scapular humeral rhythm can sometimes correlate with shoulder injury. It is difficult to demonstrate normal scapular rhythm if the scapula is not properly aligned on the ribs. When this occurs, the team addresses malposition to try to prevent injury. A MLB starting pitcher will make 20,000 warm-up throws and pitches per year. Therefore, the identification of small alignment problems in a timely manner can have a huge impact over a full season. Shoulder problem resolution is fairly simple for many players; Appropriate exercise and soft tissue techniques can be used to lengthen the short muscles and strengthen the long muscles. If a player has anterior rotation / protraction in the shoulder, the treatment can be as simple as restoring rib cage position via breathing exercises with follow up soft tissue techniques to loosen the protractors and corrective exercise to strengthen the retractors.
Identifying asymmetry. Asymmetry is something the sports medicine team looks for on a consistent basis. Many potential problem areas are identified during the staff’s daily hands-on work with players. We also have a comprehensive screening process during spring training that includes posture assessment and various hip and shoulder measurements. Posture is compared to a vertical plumb line to confirm digital images that are recorded for each player. Key shoulder measurements may include internal (IR) and external rotation (ER) motion. Baseline data established during spring training are used to help objectively identify and quantify deficits in range of motion and/or strength that may evolve during the season. A pitcher, e.g., may lose IR Motion and ER strength during the season. The goal for the strength and conditioning professional in this case is to minimize the loss of range of motion and strength. During a lengthy Major League season, it is possible that some range of motion and/or strength will be lost, but having players participate in a comprehensive in-season conditioning program that includes flexibility and resistance training can help minimize the losses.
For Little League, youth, select and high school players, the question is when do you start the screening process? This is often a factor of practicality, but I’m a big believer in getting as much information as you can as early as you can. How critical is it to know that a nine-year-old lacks internal rotation? It may not be a major competitive issue but from a data perspective, it’s priceless. Dr. Keith Meister, team physician for the Texas Rangers, and colleagues at the University of Florida measured humeral retroversion on 294 baseball players ranging in age from 8 to 16. The data showed that children can show baseball specific structural adaptation at a very early age1.
The attached photos demonstrate two basic shoulder screening measurements that can be used with players of all ages and levels of play2. For the data to have relevance, we have learned that it is important that the person administering the tests conducts them in a reliable way, i.e., he/she follows a consistent protocol every time. In these examples it is important to stabilize the scapula and standardize the amount of pressure the proctor uses at end range. It’s also better if the same person administers the tests each time.
From a rehab perspective, these measurements can be used to indicate the effectiveness of the rehab program when working with injured athletes. A strength and conditioning coach can use the same information to monitor changes in performance and make appropriate adjustments. These particular measurements may not be the holy grail of sports, but any information is helpful when it comes to injury prevention. It is ideal to be able to identify your program objective and then prescribe an exercise regime that results in the specific adaptation that you are intending.
It’s the practitioner’s job to help foster health in young athletes and enable them to learn and experience the values that sports have to offer. Guiding them onto a healthy track will have no negative effects. Coaches should be encouraged to conduct some type of screening and record relative measurements. Knowledge is a key to good health and successful, injury-free performance.
1. Regan, KM, Meister, K Horodyski, MB, Werner, DW, Carruthers, C and Wilk, K. Humeral retroversion and its relationship to glenohumeral rotation in the shoulder of college baseball players. Am J Sports Med, 30(3):354-60, 2002.
2. Cools AM, De Wilde L, Van Tongel A, Ceyssens C, Ryckewaert R, and Cambier DC. Measuring shoulder external and internal rotation strength and range of motion: comprehensive intra-rater and inter-rater reliability study of several testing protocols. J Shoulder Elbow Surg. 10:1454-61, 2014.
Nate Shaw, ATC, RSCC, is the Major League Strength and Conditioning Coordinator, Arizona Diamondbacks.
*This post is a revision of an article that originally appeared in the Performance Conditioning Baseball/Softball Newsletter.