Preventing Arm Injuries in Overhead Athletes, Part I

Many sports — including baseball, softball, tennis, swimming, volleyball, javelin throwing, and football to name just a few — require repetitive overhead motions. These motions demand extreme mobility in the shoulder complex coupled with muscular stability, strength, power, and endurance. Athletes who lack any of these individual components are at increased risk for overuse injuries. While the majority of arm injuries develop over time through cumulative trauma, many overuse injuries common to these sports can be prevented with appropriate resistance training programs designed to strengthen the muscles responsible for  overhead motions.

Despite the amount of time athletes of all ages spend every day refining their skills, they often lack the necessary strength in their shoulder to withstand the repetitive stresses of competition. By learning what athletes can do to “prehabilitate” their shoulders before an injury occurs, coaches and trainers can help improve their performance and durability, which may extend their playing careers.

Biomechanics of the Overhead Motion

When analyzing the biomechanics of the overhead motions of various sports, it is easy to see how remarkably similar a baseball pitch is to a tennis serve, a football pass, a volleyball spike, a javelin throw, a free-style swim stroke, etc. These explosive overhead motions stress the arm to its biomechanical limits. With the exception of swimming, all of these overhead motions begin from the ground and require the transfer of energy from the feet, into the legs, through the trunk, into the shoulder, up the arm, and out through the hand. As the energy reaches the shoulder, the forearm externally rotates to become parallel with the ground in preparation of the extreme acceleration at the shoulder.

During a baseball pitch, the internal rotators accelerate the arm concentrically from the position of maximal external rotation to ball release at velocities of 6,100-9,000˚/sec (Beneka, Malliou, Giannakopoulos, Kyrialanis & Godolias, 2010; Zheng, Flesig & Andrews, 2002), making it one of the fastest motions in all of sport. The external rotators of the shoulder are then responsible for decelerating and stabilizing the arm during follow-through (Saccol, Gracitelli, da Silva, Laurino, Fleury, Andrade & da Silva, 2010). Just as a chain is only as strong as its weakest link, the extreme range of shoulder abduction and external rotation needed during these motions can alter soft tissues such as ligaments and capsular structures, increasing susceptibility to injury (Lucado, Kolber, Cheng & Echternach, 2010).

Common Causes of Shoulder Injury

Cause #1: Overuse

Overhead motions such as throwing, swimming, and serving in tennis repetitively place the shoulder in vulnerable positions possibly leading to impingement syndrome” (Tyler, Nicholas, Roy & Gleim, 2000). In elite swimmers competing in the freestyle and butterfly strokes, anywhere between 40-70% have reported shoulder pain (Yanai, Hay, & Miller, 2000), making it the most common orthopedic issue seen in competitive swimmers (Swanik, Swanik, Lephart, & Huxel, 2002).

Most competitive-level baseball injuries receiving medical attention do not happen because of one particular pitch, but rather through the cumulative micro-trauma which likely began at the youth level (Lyman, Fleisig, Andrews, & Osinski, 2002). In one study, researchers compared 95 adolescent pitchers who had had either elbow or shoulder surgeries to a control group of uninjured pitchers. The study found the injured group had pitched significantly more months, games, innings, pitches per year, pitches per game, and warm-up pitches before a game. Data suggested that the chances of getting injured increase five times when pitching more than eight months out of the year and four times more likely if the player threw more than 80 pitches per game (Olsen II et al., 2006).

If we look at the number of overhead motions these athletes make on a consistent basis, we can quickly see that a tennis player can easily serve over 100 times per match, starting baseball pitchers often throw upwards of 100 pitches per game, and — while the swimming motion is not as explosive as the others — swimmers are repeating the same motion thousands of times if they are swimming more than 1600m. Most young athletes are not training their body appropriately to handle the stress of these overhead motions.

Cause #2: Higher Velocities

Just as you are more likely to get severely injured in an accident with a car going 65 mph vs. going 25 mph, higher velocities puts more stress on the arm. The faster the overhead motion — in any sport — the more motive torque (needed to start the motion and generate high arm speeds) and resistive torque (needed to slow the arm down during follow-through) is generated at the elbow and shoulder joints.

In a study comparing relative torques experienced at the elbow during the acceleration phase of throwing, 10-year-old baseball pitchers experienced greater torque than professional pitchers (Campbell, Hagood, Takagi, McFarland, Volk & Silberstein, 1994). The rotator cuff muscle group (supraspinatus, infraspinatus, teres minor, and subscapularis) is primarily responsible for stabilizing and decelerating the arm within a few hundredths of a second (Fleisig & Escamilla, 1996) during follow-through. The rotator cuff originates on the scapula, which is the anchor for the rest of the arm. As a result, both the strength of the rotator cuff and the integrity of the stabilizing muscles of the scapula (mid & lower trapezius, rhomboids, serratus anterior) must be maintained. Performing an overhead movement with an insufficiently stabilized scapula would be like firing a shotgun with one hand and expecting to handle the kickback. The scapula needs to be stable to begin with, which then allows the rotator cuff to properly decelerate the arm during follow-through. Since the velocity of throws, serves, spikes, etc. naturally increases with maturity, the stresses placed upon a developing young shoulder and elbow can significantly increase before full maturity is reached.

Cause #3: Lack of Functional Range of Motion

Many times throughout a sport season,  athletes of various overhead sports can lose shoulder range of motion due to tightness in specific muscles of the shoulder complex, which often include: pectoralis major/minor, latissimus dorsi, teres major, rhomboids, subscapularis, teres minor, infraspinatus, and posterior deltoid (Kendall, McCreary, Provance, Rodgers, & Romani, 2005). As both age and years of tournament play increase in tennis players, an overall loss of shoulder internal rotation has been shown to develop in the dominant arm (Kibler, Chandler, Livingston & Roetert, 1996). Oftentimes athletes can experience the feeling of a “dead arm” when they notice a significant loss of power in their motion. This is an indication of an overworked shoulder, no matter what the sport, and the ultimate culprit that starts this pathologic cascade is a tight posterior capsule. If we could prevent this from developing in the first place, we could prevent the dead arm syndrome (Burkhart, Morgan & Kibler, 2003).

Ironically, it seems that the inability to generate power in the dead arm syndrome could ultimately be due to the inability of the shoulder muscles to properly decelerate the arm during follow-through. Therefore, early detection and prevention is a must because clinical studies have shown that alterations in flexibility or muscle imbalance are very common in patients with shoulder injuries (Burkhart, Morgan & Kibler, 2003).

Fitness professionals can easily perform the following muscle length assessments on their athletes to determine which muscles might be tight (Kendall, McCreary, Provance, Rodgers, & Romani 2005).

Recommended Muscle Length Tests

To test accurately, position athlete supine on a hard table, with knees bent and feet flat, being sure to maintain a neutral spine; any compensation for movements by the trunk will appear to be greater ranges of motion in the shoulder.

• Pectoralis Minor: With the athlete's arms by their sides and palms up, observe the shoulders in relation to the table. Normal length allows the shoulders to be flat on the table. Tightness is measured by the extent to which the shoulders are raised from the table, and by the amount of resistance to downward pressure on the shoulder.

Normal	Tight (right forward shoulder)

• Pectoralis Major: The athlete's shoulder is externally rotated and abducted 90° (to target the upper fibers) and then abducted 135° (to target the lower fibers). Normal length allows the arm to drop to table level, with the low back remaining flat against table, and without trunk rotation. Excessive length is noted if the arm is able to drop below table level, which is not uncommon.

Normal (upper fibers)	Normal (lower fibers)

• Latissimus Dorsi, Teres Major, Rhomboids: Without arching the low back off the table, instruct athlete to raise both arms completely overhead. Normal length allows the arms to lay close to the head at table level. Tightness is noticed by the inability to get the arms to table level, and can be measured the number of inches the elbow is above the table.

Normal	Tight

• Internal Rotators (Subscapularis, Pectoralis Major, Teres Major, Latissimus Dorsi): With the athlete's elbow flexed at 90° and the shoulder abducted 90°, allow the forearm to drop back toward table level. Normal length allows the arm to be level. In overhead athletes, however, it is not uncommon to notice excessive range of motion of the dominant arm.

Normal	Excessive Range

• External Rotators (Infraspinatus, Teres Minor, Posterior Deltoid). With the athlete's elbow flexed at 90° and the shoulder abducted 90°, the fitness professional should support the elbow and allow the forearm to drop forward toward table level. If there is substitution in the scapula during internal rotation, manually hold the tested shoulder down against the table (removing any scapular motion). Normal length allows forearm to be approximately 20° from table level. Excessive tightness is often noticed in overhead athletes with limited range of motion.

Normal	Excessive Tightness

Recommended Static Stretches

After completion of the muscle length tests, the athlete should follow an injury prevention program which includes stretching the noted tight muscles to restore proper flexibility (Myers, Laudner, Pasquale, Bradley & Lephart, 2006). Daily stretching of the posterior shoulder capsule resulted in greater range of internal rotation and decreased incidence of injury in tennis players when compared to a control group (Kibler, 1998). The specific stretches necessary to focus on (depending on the findings) are shown below (Burkhart et al., 2003).

The fitness professional should instruct athletes performing these stretches to start by slowly lengthening the targeted muscle through a full range of pain-free-motion, and hold the end range for at least 30 seconds. Repeat as needed.

Latissimus Dorsi, Teres Major, Rhomboids	Mid Thoracic	Pectoralis Major/Minor
External Rotators (Infraspinatus, Teres Minor, Posterior Deltoid)

Cause #4: Lack of a Proper Warm-Up

Poor preparation for the overhead motion can create multiple stresses on the arm. Most athletes usually do a few arm circles to loosen up. The overhead motion is just like any other kind of physical activity, however; you have to properly warm up the specific muscles you are recruiting to achieve full potential and to avoid injury. Resistance tubes are commonly used in physical therapy rehabilitation programs. Since the overhead motions across many different sports are so closely related, many physical therapists use similar exercises to prescribe to athletes in order to gain necessary strength in the shoulder. Using electromyography, researchers from the University of Pittsburgh tested 12 of the most agreed-upon exercises by Certified Athletic Trainers, coaches, and players affiliated with baseball. They determined which exercises were the most effective in facilitating activation of all the shoulder muscles believed to be important for the overhead motion (rotator cuff, scapular stabilizers, and humeral movers) (Myers et al., 2005). Their goal was not to find the best exercise for individual muscles, but rather find the best exercises that activated the most muscles.

The results of the study noted above suggest that there are seven essential exercises that should be performed prior to overhead activity (see Table 1). Using light tubing to allow full range of motion, athletes should perform 1 set of 12-15 reps of each exercise in Table 1 as part of a regular warm-up routine.

Table 1: Warm-Up Exercises

Exercise	Start & End Position	Cues
External Rotation @ 90º Abduction		Keep elbow at shoulder height while rotating up to 90º.
Shoulder Flexion		Keep elbow straight while flexing shoulder up to 90º.
Shoulder Extension		Pull arm back tight to body.
Low Scapular Rows		Pull elbow back tight to body.
Throwing Acceleration		Keep stride consistent with normal pitching motion. Go through throwing motion with tube hitting on the shoulder.
Throwing Deceleration		Keep normal stride length and start in follow through position. Flex shoulder capsule bringing arm up to shoulder height.
Scapular Punches		Keep elbows locked, pretending there is a pencil between the shoulder blades, then extend your back up to the ceiling.

Sports requiring repetitive overhead motions stress the soft tissues of the shoulder to their biomechanical limits. As a result, posterior shoulder tightness can develop from the constant acceleration and deceleration forces, altering the mechanics of the shoulder joint and possibly leading to injury. Trainers and coaches can detect problems early on by regularly performing muscle length tests to look for signs of reduced range of motion. Armed with this information, they can then determine appropriate flexibility exercises and implement a regular warm-up routine to effectively prepare the shoulder for competition.

Building from this knowledge base, Part II of this article will help trainers and coaches identify the right muscles to strengthen for enhanced overhead movement, as well as design proper strength training programs with exercises targeted for the specific needs of the individual athletes they train.

References

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