Summiting shoulder injuries: prevention, rehabilitation, and return to sport

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As a ball-and-socket joint, the shoulder allows for a great range of motion and movement velocities and is exposed to contact. The upper limb is fundamental in various sports with varying demands (see table 1)⁽¹⁾. Shoulder injury prevention is complex, and establishing a testing battery that can be used across the board in different sports to assess return to sport (RTS) readiness is difficult. For example, throwing is one of the fastest human motions reaching a maximum humeral internal rotation (IR) velocity of about 7000 – 7500°/s and external rotation (ER) of 1658 – 1758°/s⁽²⁾.

Table 1: Classification of throwing sports⁽¹⁾

Risk factors

Establishing the shoulder’s primary movement and velocity during different sports is crucial as it guides injury prevention and diagnosis. Furthermore, practitioners need to consider risk factors such as reduced range of motion (ROM), muscle weakness compared to individual baseline or group normative values, imbalance in rotational strength, changes in load, player position, participation level, a history of shoulder pain, and psychosocial factors⁽¹⁾. These risk factors need to be assessed to see which ones are present to compile a rehabilitation plan for the injured athlete and a prevention plan for the uninjured. In addition, different sports will require focused rehabilitation plans to target specific muscles.

Practitioners can divide risk factors into two categories: modifiable and non-modifiable. Modifiable risk factors include ROM and strength, whereas non-modifiable factors include age and sex⁽²⁾. For example, pre-season assessment in above-shoulder throwing athletes established the following as increasing the risk of shoulder injuries: training and competitive load, reduced glenohumeral IR ROM (GIRD), arm fatigue, reduced total ROM, strength deficit in external rotators and inadequate scapular position⁽²⁾.  

Screening

The relationship between training load, fatigue, and injury is not linear. There are a lot of variables to consider, and most of these variables affect other variables. The effectiveness of screening is debatable, yet practitioners continue to try and find links between training demands, biomechanics, and other so-called risk factors and injury. To establish the risk factors, one needs to screen the athlete to gather baseline information about the current shoulder performance and the athlete as a whole (see table 2). Practitioners can screen athletes at the start of the pre-season and should repeat the screening throughout the season to assess for changes in strength and ROM⁽¹⁾. Typical tests include assessing glenohumeral mobility and rotator cuff strength along with functional tests such as the Upper Quadrant Y-Balance, Closed Kinetic Chain Upper Extremity Stability Test, and the Seated Medicine Ball Throw⁽²⁾. There is a moderate to high correlation between the seated medicine ball throw test outcome and elbow and shoulder strength⁽²⁾. The Closed Kinetic Chain Upper Extremity Stability Test score only showed a moderate correlation of shoulder strength⁽²⁾. Screening is vital to establish the possible risk factors and provides insight for injury prevention and guidance during the RTS process.

Table 2: Screening the shoulder⁽²⁾

Load monitoring

Athlete load monitoring provides information about how much external stress the shoulder can withstand. Load monitoring aims to prevent injury and establish possible risk factors. Practitioners use different load monitoring methods, including internal and external processes. Some methods have various barriers to implementation, such as human resource requirements (experience) and financial costs. These include radar guns to determine the velocity demands and global positioning systems (GPS). Practitioners can use GPS to profile activities and quantify the training demands as it is an acceptable, reliable, and valid measure of velocity, acceleration, and distance⁽³⁾. However, some tools have low barriers to implementation. For example, the number of repetitions/throws per innings or game can assist practitioners in identifying the load demands⁽¹⁾.

Internal load-capturing methods include the sessional rating of perceived exertion (RPE) and self-report wellness questionnaires. Practitioners can use RPE for the shoulder specifically or the session. Furthermore, they can use self-reported wellness questionnaires sensitive to subtle changes in training load^(1,3). Methods such as RPE and questionnaires are only reliable and valid if recorded consistently, and in a manner all athletes understand. Despite its shortcomings, the acute:chronic workload ratio can assist practitioners in quantifying and communicating training load to coaches and players⁽³⁾.

Despite the complexity of using load management to identify injury risk, practitioners can use normative population data to raise red flags and increase vigilance around high-risk athletes. For example, a high overall shoulder-specific load of more than 16 hours per week, along with significant weekly load increases (>60% compared to the average of the previous four weeks) in training and matches, may increase injury risk⁽¹⁾.

Shoulder rehabilitation

When designing injury rehabilitation programs, practitioners use athlete- and sport-specific factors⁽¹⁾. Clinical pathways and protocols often dictate exercise prescription based on the diagnosis. However, understanding muscle structure, function, metabolism, and movement allows for innovative program design tailored to each athlete. Incorporating appropriate load, low irritability, and low symptom response guides the progression and treatment⁽¹⁾. There are four focus areas to support athlete rehabilitation:

1. Improve sport-specific biomechanics
2. Challenge capacity by increasing the training intensity
3. Load the athlete from a physiological and psychological perspective
4. Involve the multidisciplinary team in a shared decision-making process

If the athlete is experiencing high irritability (high pain levels at rest, night pain, high disability), the focus is to manage the pain and minimize tissue stress⁽²⁾. If this is during the early rehabilitation phases, practitioners can use shoulder symptom reduction tests to guide exercise and treatment choices⁽²⁾. These exercises aim to reduce existing symptoms by doing active or passive correcting exercises such as a posterior glide of the humeral head and upward rotation of the scapula during active elevation.

If the athlete is experiencing low irritability (low pain levels, pain only during activity, no night pain), the focus is to increase tissue capacity by increasing physical tissue stresses⁽²⁾. Throughout the rehabilitation process, the athlete should continue to strengthen and condition the trunk and lower extremities⁽²⁾. The practitioners must find the ‘sweet spot’ when prescribing exercises to ensure optimal adaptations.

Return to Sports

The first thing a coach and athlete want to know is how long it will take the athlete to RTS. However, RTS rehabilitation is complex as sports are chaotic, and the loss of capacity due to injury will impact RTS timelines. All stakeholders need to understand the social, physical, and psychological factors in the RTS continuum⁽²⁾. Fear of re-injury, self-efficacy, and motivation all influence the treatment plan and the outcome after injury⁽²⁾.

Regaining full ROM to RTS is not a prerequisite for most sports. However, some have specific end-range demands⁽¹⁾. For example, full ROM is not a priority for collision/contact sports and athletes performing below shoulder height⁽¹⁾. Strength, power, and endurance encompass the majority of factors, such as rate of force development (RFD), peak force, contraction velocity, and fatigue resistance which are all sport-specific⁽¹⁾. However, the key capacity requirements differ according to the demands of the sport. For example, below-shoulder height throwing athletes require speed and deceleration with the follow-through⁽¹⁾. Whereas collision sports require stability and bracing abilities⁽¹⁾. Finally, above-shoulder-height athletes need power, strength, and endurance⁽¹⁾.

The kinetic chain is segments linked together that function in a proximal-to-distal sequence of energy transfer, with the velocity being produced at the proximal segments and then transferred to the distal segments⁽¹⁾. For a kinetic chain to be efficient, it generates, facilitates, and aggregates controlled mechanical energy transfer to enhance performance⁽¹⁾. When an athlete sustains an injury, the whole chain becomes inefficient, as one segment can no longer function optimally. Therefore, the more distal parts need to compensate to avoid the loss of energy^(1,2). For this reason, shoulder assessment and management should extend to the whole kinetic chain, such as the trunk, lower extremities, and distal arm joints⁽²⁾. It is vitally important that an athlete feels psychologically ready before moving on to the next phase of the continuum. Furthermore, practitioners must consider the player’s position when designing RTS programs⁽¹⁾.  

Prevention

Preventing shoulder injuries involves strengthening the whole body and focusing on the areas used during the throwing action in a full ROM⁽⁴⁾. Warm-up is a crucial element of injury prevention, and above-shoulder, throwing athletes should perform a comprehensive, holistic pre-exercise routine to reduce their injury risk (see table 3). These exercises activate each of the rotator cuff muscles. Practitioners and coaches should educate collision/contact athletes on the proper safety equipment requirements and correct falling techniques⁽⁴⁾. The most important prevention strategy for all throwing athletes is instilling the proper technique.

Table 3: Whole body baseball prevention approach for different phases of the throwing action⁽⁵⁾

Conclusion

The assessment, monitoring, rehabilitation, and prevention of shoulder injuries remain challenging due to the demands placed on the joint during various sports. Developing a gold-standard assessment tool is difficult as sport-specific and positional-specific demands vary depending on the multiple social, psychological, and physical factors. Establishing the risk factors is critical to ensure that the rate of shoulder injuries is as low as possible. Teaching the correct techniques from a young age is vital, along with proper strength and mobility programs and the implementation of easy but reliable and valid load monitoring methods.

References

1. J Orthop Sports Phys Ther 2022;52(1):52.
2. Ann Phys Rehabil Med. 2021 Jul;64(4):101384.
3. Sports Med 2016 46:1503-1516
4. McGraw-Hill Education, 2017. Principles of Athletic Training. A Guide to Evidence-Based Clinical Practice, 16^th Edition
5. Current Reviews in Musculoskeletal Medicine (2022) 15:53-64