Abstract Key Points Competitive swimmers less than 12 years of age had substantial shoulder pain, and older swimmers had pain, dissatisfaction, and disability. High school swimmers were the most symptomatic and incurred the greatest load in terms of hours swum per week and per year. Shoulder pain, dissatisfaction, and disability were correlated positively with increased upper extremity usage in terms of swimming or water polo exposure and were correlated negatively with participation in another sport, specifically soccer for young and running or walking for mature swimmers. Symptomatic swimmers who were less than 12 years of age had reduced shoulder flexibility, weakness of the middle trapezius and shoulder internal rotators, and latissimus dorsi tightness, whereas symptomatic swimmers who were 12 years of age or older had pectoralis minor tightness and decreased core endurance. Because female competitive swimmers have shoulder pain and disability throughout their lives, a program to prevent shoulder injury that might lead to pain and dysfunction is warranted and might include exposure reduction, cross-training, pectoral and posterior shoulder stretching, strengthening, and core endurance training. Each year, millions of people swim for exercise and recreation. Competitive swimmers might practice 5 to 7 days per week and sometimes twice daily. They have shoulder pain at a reported prevalence of 40% to 91%. 1-3 Shoulder pain can be so severe that it leads to functional impairments and termination of participation. A relationship between exposure, which is defined by distance or time spent swimming, and shoulder pain exists, 3 but exposure might not be the only factor related to shoulder pain. Physical impairments found in symptomatic swimmers include reduced shoulder internal rotation strength and external rotation and abduction muscle endurance. Over the past decade, changes have been made in competitive swimming training and equipment, such as more extensive dry-land programs and the use of redesigned paddles to improve stroke mechanics. Given these changes and the high prevalence of pain in swimmers, potentially modifiable physical characteristics of swimmers' exposure and training variables that are related to their pain need to be identified. No researchers have combined training and exposure data with physical examination findings to identify factors related to shoulder pain over an age range from the young team competitor to the master's-level swimmer. Therefore, the purpose of our study was to determine whether physical characteristics, training methods, or exposure differs between swimmers with and without shoulder pain, dissatisfaction with their shoulders, and disability over 4 age groups representing the swimmer's lifespan. Identification of factors that differentiate swimmers with and without shoulder pain could provide the basis for a program to prevent shoulder injury that might lead to pain and dysfunction. Go to: METHODS Participants A total of 236 female swimmers from 8 to 77 years of age volunteered for this multicenter study. Each participant belonged to a youth, high school, or US Masters swim team. Swimmers in the Philadelphia, Pennsylvania, area were invited to participate with their coaches' approval. Adult swimmers and parents or guardians of minors provided written informed consent, and minors signed an assent form. The study was approved by the Arcardia University Institutional Review Board. Procedures Adult swimmers and the parents or guardians of minors completed or assisted with a survey that included demographics, questions about other sport participation, and the amount of participation in swimming on a weekly basis. They also were instructed to indicate the number of months per year they practiced and how many years they had participated in competitive swimming. Shoulder pain and dissatisfaction were assessed using the respective subscales of the Penn Shoulder Score. Next, swimmers rotated through a series of 5 stations where range of motion (ROM), strength, pectoral muscle length, core endurance, and scapular dyskinesis were assessed by members of the research team. This team consisted of an experienced physical therapist (A.T.) and 4 graduate physical therapist students (G.N.T., S.E.K., C.J., A.S.), 2 of whom were certified athletic trainers (G.N.T., S.E.K.). Before data collection on swimmers, 2 training sessions were held in which the research team was given written instructions and practiced the testing procedures. Intrarater reliability of ROM, strength, pectoral muscle length, and scapular dyskinesis was established with 14 athletically active females (age = 23.8 ± 1.7 years). Athletically active was defined as exercising regularly or participating in sports. Intraclass correlation coefficients (ICCs) for continuous data from strength measured by dynamometry, ROM, and pectoral length were fair to excellent (ICC [3,1] = 0.60 to 0.92), and percentage agreement for scapular dyskinesis and manual muscle testing was excellent (κ = 0.83 to 1.0). Station 1: Range of Motion. Passive ROM (PROM) of both shoulders was assessed using an inclinometer for shoulder flexion in neutral rotation with the participant lying supine; shoulder flexion, with the elbow maximally flexed for long head triceps tightness 10 ; shoulder flexion, with the humerus externally rotated, knees and hips flexed, and abdominal muscles actively contracted for latissimus dorsi tightness 10 ; and internal and external rotation, with the shoulder abducted to 90°. Station 2: Strength. Bilateral glenohumeral strength was assessed using a handheld dynamometer (microFET; Hoggan Industries, Draper, UT). For this study, maximal isometric force production was tested for shoulder internal and external rotation with the participant lying prone and the shoulder abducted to 90°; this position has been recommended because swimmers are familiar with it and because it is comfortable and has the highest torque values. 11 Shoulder horizontal abduction strength was measured with the participant lying prone with the elbow extended, and shoulder elevation was measured with the participant standing in the empty-can position (90° of shoulder elevation in the scapular plane and internally rotated). Two repetitions of each test were performed, and an additional repetition was performed if the difference between the first 2 measurements was greater than 1.36 kg. Arm and forearm lengths also were measured and used to calculate normalized torque values, which were obtained by multiplying the dynamometer output by the distance from the shoulder to the application of force and then dividing by body mass. Manual muscle testing was performed bilaterally on the serratus anterior, lower trapezius, and middle trapezius muscles as described by Kendall et al. Station 3: Scapular Dyskinesis. Scapular motion patterns were assessed for winging or dysrhythmia using the scapular dyskinesis test (SDT). The SDT has demonstrated reliability and validity in adult athletes participating in sports that include overhead use of the upper extremity, specifically swimming and water polo. 12,13 Shoulder flexion and abduction each were performed 5 times bilaterally with dumbbells. A 0.45-kg dumbbell was used for participants who weighed less than 36.29 kg, 1.36-kg dumbbells were used for participants who weighed from 36.29 to 68.04 kg, and 2.27-kg dumbbells were used for participants who weighed more than 68.04 kg. These weights were selected based on a pilot study in which Tate et al 14 determined that swimmers could lift the required amount safely. The examiner observed the scapulae from a posterior view and graded the motion pattern as normal or subtle dyskinesis or obvious dyskinesis. Station 4: Endurance. Endurance of core musculature was assessed using the side bridge test Station 5: Pectoralis Minor Length. Pectoralis minor length was measured with a PALM palpation meter (Performance Attainment Associates, St Paul, MN) using surface landmarks validated by Borstad 18 Data Analysis Participants were divided into 4 groups by age, based on the similarity of hours of training and competitive level: ages 8 to 11 years (n = 42), 12 to 14 years (n = 43), 15 to 19 years (high school, n = 84), and 23 to 77 years (masters, n = 67). These groups had different swimming exposures, with respective means of 6.9 ± 2.4, 10.1 ± 4.3, 16.1 ± 6.0, and 4.0 ± 1.7 hours swum per week (P < .001). Cases were classified as positive or negative for substantial pain, dissatisfaction, and disability (PDD) based on the total of the Penn Shoulder Score pain scale and the satisfaction question (range, 0-40, with 40 indicating no pain, fully satisfied) and the total score for swimming disability using the DASH sports module (range, 4-20, with 4 indicating no swimming disability). For the 3 oldest groups (age > 11 years), a positive case (+PDD) had to meet 2 criteria: (1) The DASH sports module score was greater than 6 points and (2) the Penn Shoulder Score was less than 35 points. For the DASH sports module, a score greater than 6 points requires the swimmer to have at least mild difficulty in 3 of the 4 areas (difficulty with usual technique, swimming because of pain, swimming as well as she would like, and spending usual amount of time practicing swimming) or moderate or severe difficulty or inability in at least 1 of the 4 areas. A Penn Shoulder Score of less than 35 points for pain and satisfaction reflects change greater than 5 points, which exceeds the total error (standard error of the mean) for the combined pain and satisfaction sub-scales. 8 All cases not satisfying the requirements for +PDDs were classified as −PDDs. In the youngest group (age range, 8-11 years), only 1 of 42 swimmers fit the +PDD definition used for the older participants, which precluded further data analysis. Therefore, in the 8-to 11-year-old age group, a case was considered positive if the swimmer rated her pain equal to or greater than 2 of 10 with strenuous activity on the Penn Shoulder Score pain scale. All cases that did not satisfy the requirements for +PDDs were classified as −PDDs. For swimmers with bilateral symptoms, the data from the most painful side were used for +PDDs. For swimmers with equal pain bilaterally or no pain, the participants were listed in consecutive numeric order based on age, and alternate sides were selected. Continuous variables for participant demographics, exposure, and physical examination were compared using independent t tests. Categorical variables were compared using χ 2 tests. When we found categorical variables in which 20% of the cells did not contain a minimum of 5 cases and therefore did not meet the assumption of expected cell frequency, we used a Fisher exact probability test. A 1-tailed test was used for the variables we hypothesized had a directional preference based on pilot data: history of traumatic injury, unilateral breathing pattern, and participation in water polo. 14 A 2-tailed test was used for all other variables. To determine whether stroke specialty (butterfly, backstroke, breaststroke, or freestyle) was associated with pain and disability, the data from all age groups were combined because a failure to meet minimum cell count for χ 2 occurred within each age group. We used SPSS (SPSS Inc, Chicago, IL) for data analysis. Go to: RESULTS The number of +PDDs was 9 of 42 (21.4%) in swimmers aged 8 to 11 years, 8 of 43 (18.6%) in swimmers aged 12 to 14 years, 19 of 84 (22.6%) in high school swimmers, and 13 of 67 (19.4%) in masters swimmers. Participant demographics for +PDDs and −PDDs are presented in DISCUSSION Competitive swimmers are at risk for developing shoulder pain and disability, which can lead to dissatisfaction with the use of their shoulders during swimming and daily activities. Although specific differences in swimmers with and without symptoms have been investigated extensively, we are the first to our knowledge to collectively use validated and reliable methods to test groups of swimmers poolside without expensive, labor-intensive equipment. This method has allowed us to assess physical performance and exposure variables in competitive swimmers aged 8 to 77 years and to document the presence of shoulder symptoms throughout the lifespan of swimmers. Potential factors related to shoulder pain and disability are exposure time to swimming, training methods, and physical characteristics of the swimmers. We found that 18.6% to 22.6% of competitive swimmers in each of our 4 age groups experienced shoulder pain and disability. Swimmers less than 12 years of age primarily had pain, whereas participants more than 12 years of age experienced pain, dissatisfaction, and disability with the use of their shoulders. The high school swimmers were the most symptomatic. Factors related to shoulder pain, dissatisfaction, and disability with shoulder use in 2 or more age groups were greater swimming exposure, a history of traumatic shoulder injury, participant-rated feeling of instability, and reduced participation in another sport or activity (cross-training). Additional factors associated with symptoms in only a single age group were less shoulder flexion ROM, less strength of shoulder internal rotation and the middle trapezius, shorter pectoralis minor, latissimus dorsi tightness, more participation in water polo, bilateral breathing, and less core endurance. We found significant differences between participants with and without shoulder pain, disability, and dissatisfaction in exposure and physical characteristics but found no differences in age, height, mass, or body mass index. For all age groups, the +PDD group had greater exposure than the −PDD group in terms of years swum and of hours per week and hours per year practiced; however, we found differences in exposure only in the high school and masters groups. High school swimmers in the +PDD group had 1.50 ± 1.14 years more swimming exposure than those in the −PDD group. In a study of elite competitive swimmers aged 13 to 25 years, Sein et al 3 found a correlation between years of training and supraspinatus tendon thickness on magnetic resonance imaging. They reported that all swimmers with tendon thickening had supraspinatus tendinopathy and shoulder impingement pain. In our study, both +PDD and −PDD swimmers averaged more than 15 hours per week of swimming, and some swimmers reported swimming 10 000 m or more daily. Sein et al 3 also found that athletes who swam more than 15 hours per week were twice as likely to have tendinopathy as those who trained less. This might help explain our finding that high school athletes had the highest levels of pain and disability. Allegrucci et al 2 estimated that competitive swimmers performing 10 stroke cycles per 25 m and covering 10 000 m per day would incur 4000 shoulder revolutions daily. Given that repetitive upper extremity usage at or above shoulder level has been identified as a risk factor for shoulder pain, it is not surprising that those with greater exposure have pain and disability. In the masters group, the +PDD group swam a greater number of hours per year (223.60 ± 81.81 hours) than the −PDD group (163.88 ± 81.22 hours), and a trend was seen for hours swum per week. The association between exposure and pain and disability in our study is consistent with that reported in other studies, in which the presence of supraspinatus tendinopathy in elite swimmers was predicted 85% of the time from hours swum per week alone or in combination with distance swum per week. 3 Although pitch-count rules exist for youth baseball pitchers, no exposure recommendations are available to guide coaches of youth competitive swimmers. Whereas increased swimming exposure and participation in water polo were positively associated with pain and disability, other findings had a negative association. Specifically, the 8-to 11-year-old −PDD swimmers more frequently participated in another sport, with soccer specifically reported, and the −PDD masters swimmers more frequently participated in a walking or running program than their symptomatic counterparts. Independent t tests revealed no difference in the amount of time spent swimming in terms of hours per week, hours per year, or years of participation between the groups that did and did not participate in these activities. Although we cannot conclude that participation in other activities offers a direct protective mechanism, these findings lend support to the concept of cross-training. Investigators of the effects of cross-training have concluded that adolescents participating in several sport and exercise activities throughout the year were less likely to experience neck, shoulder, or low back pain. Whereas Richardson and colleagues 23 found that unilateral breathing patterns increased the risk of shoulder problems, we found that the 8-to 11-year-old +PDD group had a greater incidence of a bilateral breathing pattern. Young swimmers may lack appropriate stroke mechanics, but this cannot be determined from our study. Although a trend existed for the +PDD group to breathe unilaterally at the high school level, we found no differences in breathing patterns among the other 3 age groups. A history of a traumatic injury to the shoulder, such as a dislocation, fracture, or fall, was reported more frequently in the +PDD group in swimmers from 3 groups (age 12 years through masters). These injuries may have left residual deficits that pre-disposed them to pain and disability. Similarly, +PDD swimmers in the 12-to 14-year-old and high school groups more frequently answered "yes" when asked, "Does your shoulder feel unstable, or do you feel like it ever 'slips' out of place?" These findings suggest that swimmers with previous injuries or instability should be assessed to determine whether they have deficiencies that could be addressed to reduce the risk of shoulder pain. Although paddle use has been associated with pain, 23 our data did not show differences in swim paddle use between +PDD and −PDD groups. Paddle design has changed from solid and rectangular to a shape that conforms to the hand and is perforated to reduce resistance. In addition, coaches might be more judicious in their use of paddles because of findings reported in previous studies. Individual stroke preference was not found to differ between +PDDs and −PDDs. This finding is consistent with that of Sein et al, 3 who reported that strokes have little effect on predisposition to shoulder pain. This is not surprising because practice sessions typically involve 80% freestyle swimming. 7 Core endurance measured by time held for the side bridge position was less (8.5 seconds) in the 12-to 14-year-old +PDD group. Trends of reduced core endurance were seen for the high school and masters-level swimmers. The side and prone bridge positions evoke increased activity in the external oblique abdominis and the rectus abdominis in addition to requiring glenohumeral and scapular control. Scapular winging due to trapezius or serratus anterior fatigue would result in test termination due to loss of core position. High levels of serratus anterior muscle activity have been demonstrated for the forearm push-up plus, 24 which is essentially an isometric hold of the prone bridge exercise. Fatigue of the shoulder and trunk musculature might initiate the development of pain in the swimmer's shoulder, Reduced resting length of the pectoralis minor was found in the high school +PDD group, and a trend was seen in the youngest swimmers. People with shorter pectoralis minor muscles have displayed altered scapular kinematics, with less scapular posterior tilting and greater internal rotation during humeral elevation. Reduced posterior shoulder flexibility assessed with internal rotation PROM at 90° of abduction was found in the 8-to 11-year-old +PDD swimmers. Harryman et al 28 noted that selective tightening of the posterior capsule produced superior and anterior humeral head translation. This could reduce subacromial space during overhead upper extremity use and cause shoulder pain due to impingement. Three-dimensional videography has supported this finding by showing that people with limited shoulder internal rotation were likely to experience a large amount of mechanical impingement during the swimming stroke. 29 The 8-to 11-year-old swimmers with pain also had reduced flexion ROM with latissimus dorsi tightness. Reduced flexion ROM, which we tested with the shoulder in neutral rotation, might be attributed to capsular tightness, but reduced flexion with the pelvis posteriorly tilted and shoulder externally rotated is proposed to be due to tightness of the latissimus dorsi. If one chose to implement a stretching program to address limitations in shoulder elevation, a differentiation should be made about the restricted structure so that specific stretching exercises could be given. Theoretically, swimmers with reduced flexion ROM could have a reduced stroke length and, therefore, need additional strokes compared with swimmers with greater mobility, incurring greater shoulder load. However, because older swimmers exhibit shoulder hypermobility 7 and stretching has been reported to aggravate shoulder symptoms, 1 careful consideration should be given when evaluating potential merits of shoulder elevation stretching. Consistent with findings reported in previous studies, 6,7 none of the other age groups showed a difference in flexion ROM between swimmers with and without PDD. The frequency of obvious scapular dyskinesis was not different between the +PDD and −PDD groups in any age group. This differs from findings reported by Bak and Magnusso
