Who gets itEmerging evidence
The shoulder is one of the commonest injury sites in lifting sports, and up to 36% of resistance-training injuries are at the shoulder. In 110 elite lifters, shoulder injuries were commonest in the powerlifters, and no single exercise was linked with them. In a survey of 393 gym members, 7.4% reported a shoulder injury in 6 months, more than any other site, and in competitive powerlifters, those over 40 had more arm and shoulder injuries.
Reviews suggest wide grips, a high training load and fatigue as likely causes of bench press shoulder injuries, but there is no injury data to prove it.
Sources 1, 2, 3, 4, 5, 6, 7, 8
Weightlifter's shoulder and the torn pecEmerging evidence
Weightlifter's shoulder (distal clavicle osteolysis) is a stress reaction at the end of the collarbone, seen mostly in people who lift: 45 of 46 athletes in the first series lifted weights, and 28% of 25 Danish weightlifters had the X-ray signs. Across 8 studies (483 people), bench pressing was behind 49.1% of cases and other weight training 24.4%, and pressing more than 1.5 times body weight and weight training 3 or more times a week were linked with it.
A torn pec (pectoralis major) tendon happens almost only in men, mostly during weight training (48% of 365 published cases, and 61.9% and 63.2% in two pooled analyses), most often in the bench press as the loaded arm lowers. It needs checking the same day: see the warning signs.
Sources 9, 10, 11, 12, 13, 14, 15
Is it posture or a muscle imbalance?Mixed evidence
Rounded upper backs were no more common in people with shoulder pain across 10 studies, though sitting tall gives more arm range in the moment. Weight trainers with signs of impingement had less shoulder rotation and weaker external rotators and lower trapezius than those without, but a snapshot can't show which came first.
In recreational weight trainers, impingement signs went with lateral raises and upright rows above shoulder height, and a feeling the shoulder might slip (apprehension) went with behind-the-neck pulldowns and presses. Both were less common in people who trained their external rotators.
Sources 16, 17, 18, 19
Less common causesEmerging evidence
In 20 weightlifters with hidden instability at the front of the shoulder, pain came with the arm out to the side and turned back, as at the bottom of a wide-grip bench (our reading); 13 of 23 shoulders settled with rehab and changed technique, and 10 needed surgery. In a case series of 7 sportsmen, 5 of them bench pressers, a tender spot just inside the front of the shoulder turned out to be the pectoralis minor tendon.
Sources 20, 21
When a scan helps, and what it can't tell youEmerging evidence
Not at first for rotator cuff or AC joint pain. In 96 shoulders without symptoms, 34% had a rotator cuff tear on an MRI (magnetic resonance imaging) scan, with no full-thickness tears under 40 but more with age, and AC joint changes are common in shoulders that don't hurt.
A pop with bruising or a changed chest shape needs prompt assessment, often with a dedicated chest MRI or an ultrasound scan, because a routine shoulder MRI may miss a pec tear. Weightlifter's shoulder that isn't settling is often confirmed on MRI.
Sources 22, 23, 15, 11
How it usually goesEmerging evidence
In the largest trial (708 adults with rotator cuff problems), shoulder pain and function improved substantially over a year in every group, though not completely. An NHS booklet says about half of rotator cuff related shoulder pain settles in about 6 months and rehab takes about 3 to 6 months, and the NHS says shoulder pain can take 6 months or longer. Most people with weightlifter's shoulder recovered without surgery. After a pec repair, it takes at least 6 months to get back to full activity. No one can promise a date.
Sources 24, 25, 26, 11, 15