How Much Swimming Leads to Shoulder Pain?
By Dr. Yi-Cheng Wu · Reviewed June 21, 2026
Swimmer's shoulder often stems from supraspinatus tendinopathy, and it is associated with training more than 15 hours a week, swimming more than 35 km a week, and a high ACWR.
Swimmer's shoulder is often related to supraspinatus tendinopathy in the rotator cuff. An Australian study found that swimmers training more than 15 hours a week had roughly twice the likelihood of tendinopathy compared with those who trained less, and those swimming more than 35 km a week had roughly a fourfold increase in likelihood. A study of U.S. collegiate athletes found that injury was associated with a high acute training load and a high ACWR (acute:chronic workload ratio), with injury risk increasing when the ACWR exceeded 1.5. Most recreational swimmers rarely reach these high training volumes, so the likelihood of tendinopathy is in theory lower for them, but compensatory movements caused by poor stroke technique are also associated with symptoms.
Swimmer’s shoulder is a worry for people who love to swim. Surveys suggest that 91% of swimming enthusiasts have had shoulder pain and 84% have had a feeling of the shoulder catching (impingement). There are many causes, including the biceps tendon, the rotator cuff, and scapular instability, but one of the most common is supraspinatus tendinopathy in the rotator cuff.
A normal supraspinatus tendon is yellowish-white, with tendon cells interwoven among the collagen fibers. When it becomes diseased, the tendon changes from yellowish-white to gray, starts to become slightly swollen, and is accompanied by inflammation of the bursa.
Sometimes in clinic people ask: how much swimming increases the chance of shoulder pain?
This 2008 Australian study can tell us a few things. It enrolled 80 elite athletes aged 13-25, who swam between 8 and 29 hours a week, with a weekly swimming distance most commonly in the range of 31-40 km. Their overall condition was assessed through physical examination, instruments for detecting shoulder instability, and MRI. The study had many interesting findings.
Research findings
The four swimming strokes did not appear to be significantly associated with supraspinatus tendon thickening. Among the physical examinations that could be verified, the impingement and O’Brien tests had higher detection rates and could identify 75% of the elite swimmers with problems.
Some swimmers have shoulder joint laxity, though there are two schools of thought — some studies think it contributes and some think it does not. In this study, the degree of joint laxity was significantly associated with the swimmers’ shoulder pain, but lacked an association with supraspinatus tendinopathy. This may mean that the pain following laxity comes from other structures, such as muscles, other nearby tendons, or ligaments, rather than the supraspinatus tendon.
The occurrence of supraspinatus tendinopathy is strongly related to an athlete’s performance level, with higher-level swimmers more likely to have problems.
The training volume that most people care about: the study found that swimmers training more than 15 hours a week were more likely to have problems, with roughly twice the likelihood of tendinopathy compared with those who trained less. Recreational swimmers rarely swim more than 15 hours a week, so the likelihood of tendinopathy is in theory lower for them.
For training distance, swimmers covering more than 35 km a week had roughly a fourfold increase in the likelihood of tendinopathy compared with those swimming shorter distances, which is even harder for recreational swimmers to reach.
In sports medicine, the acute:chronic workload ratio (ACWR) based on training volume is a relatively new approach. A growing body of research confirms that a high ACWR is associated with sports injuries across many sports (such as cricket, rugby, soccer, and running). The findings indicate that when the ACWR exceeds 1.5 (that is, the acute training load is 50% higher than the chronic training load), one enters a “danger zone” of increased injury risk.
There were no earlier studies measuring the ACWR of swimming volume. In 2022, a related study of U.S. collegiate swimmers appeared. In that study, the weekly acute training volume referred to the kilometers swum that week, the weekly chronic training volume referred to the average weekly kilometers swum over that week and the previous 3 weeks, and the weekly ACWR was the ratio of the acute training load to the chronic training load (see the further reading).
The results found that injury was associated with a high acute training load and a high ACWR, but not with a high chronic workload. The injury rate under a typical training load was about 1% or less, but it rose markedly to 15% under a high acute training load and 14% under a high ACWR (in the study, the thresholds for a high acute training load and a high ACWR were 37.2 km/week and 1.56, respectively).
The training-related injury risk rose during the winter training period, especially after final exams and the winter break, which are times of reduced training volume.
Summary
Supraspinatus tendinopathy is one of the main causes of swimmer’s shoulder pain, and people who love to swim more or less develop similar symptoms. This study’s conclusions help us understand how to gauge training volume. Unlike in elite athletes, for recreational swimmers the compensatory movements that arise from poor stroke technique are strongly related to swimmer’s shoulder. In clinic I often need to ask patients to demonstrate their movements a little, and there is also room to exchange ideas with swimming coaches or strength coaches, because only through more discussion and communication can the crux be found.
Further reading
References
- J Athl Train. 2022 May 1;57(5):470-477. doi: 10.4085/1062-6050-0135.21. Workload and Noncontact Musculoskeletal Injury in Collegiate Swimmers: A Prospective Cohort Study
- Br J Sports Med. 2010 Feb;44(2):105-13. doi: 10.1136/bjsm.2008.047282. Shoulder pain in elite swimmers: primarily due to swim-volume-induced supraspinatus tendinopathy
Further reading
Frequently asked questions
What did the research find?
A 2008 Australian study of 80 elite swimmers found that the four swimming strokes were not significantly associated with supraspinatus tendon thickening; among the physical examinations, the impingement and O'Brien tests had higher detection rates and could identify about 75% of the athletes with problems. The degree of joint laxity was significantly associated with shoulder pain, but lacked an association with supraspinatus tendinopathy.
Who most needs to watch out for swimmer's shoulder?
The occurrence of supraspinatus tendinopathy is related to an athlete's performance level, with higher-level swimmers more likely to have problems. The study found that those training more than 15 hours a week had roughly twice the likelihood of tendinopathy compared with those who trained less, and those swimming more than 35 km a week had roughly a fourfold increase in likelihood. Recreational swimmers find such training volumes harder to reach.
How is training load related to swimmer's shoulder?
The acute:chronic workload ratio (ACWR) is increasingly used to assess sports-injury risk, and injury risk increases when the ACWR exceeds 1.5. A 2022 study of U.S. collegiate athletes found that injury was associated with a high acute training load and a high ACWR, with an injury rate of about 1% or less under a typical training load, rising to 15% under a high acute training load and 14% under a high ACWR.
This article is also available in the original Chinese, with the full reference list.
閱讀中文原文 · Read in Chinese