Soreness, and where you feel itStrong evidence
Delayed onset muscle soreness (DOMS) is a dull ache in the muscles you worked, starting 12 to 24 hours later, worst between 24 and 72 hours and gone within 5 to 7 days, and it is commonest after a new move, more sets or a break. After pressing it sits in the chest and the front of the shoulder; after pulling, rows and rear shoulder work, at the back of the shoulder and between the shoulder blades; after raises and overhead work, at the side of the shoulder.
How much it hurts can depend on what you expect: when researchers brought on soreness in the shoulder muscles of 42 healthy adults, fear of pain explained 16% of the next day's pain. That was a laboratory study, but it fits the advice to treat soreness as normal.
Sources 1, 2, 3
The shoulder is a common place for lifters to get hurtEmerging evidence
Up to 36% of documented resistance training injuries are at the shoulder, mostly from surveys looking back, with technique and muscle imbalance suggested but not shown as causes. In a survey of 393 gym members, 27% reported a weightlifting injury in the past 6 months, and the shoulder was the commonest site (7.4%). The weight-training sports still have low injury rates next to team sports, and shoulder injuries are fairly common in CrossFit-style training.
Sources 4, 5, 6, 7
The rotator cuff, the AC joint and a slipping shoulder
Rotator cuff related shoulder pain, often called impingement, is the commonest shoulder problem that outlasts soreness: pain on the outside of the shoulder and upper arm, a painful arc as you lift the arm out to the side, and pain lying on it or reaching behind you. Many clinicians now avoid the word impingement, because no single pinched structure can be shown to be the source. An NHS booklet says it affects men and women equally.
In snapshot studies of recreational weight trainers, signs of impingement went with lateral raises and upright rows taken above shoulder height, and signs of a loose front of the shoulder went with behind-the-neck presses and pulldowns; both were less common in people who trained the muscles that turn the arm out. Studies like these show a link, not a cause.
Sources 8, 9, 10, 11, 12
Weightlifter's shoulderEmerging evidence
Pain you can point to with one finger on top of the shoulder, at the end of the collarbone, worse with deep bench presses, dips, push-ups and reaching across the body, can be osteolysis of the end of the collarbone, where the bone thins under repeated heavy load. The numbers come from small, older series of men: in the first series, 45 of 46 athletes lifted weights, and in 25 competitive weightlifters, 7 had the X-ray changes against none of 25 controls. A 2026 review of 8 studies, which we read as an abstract only, found bench pressing linked with about half of the cases, and most people recovered with changed training. No study gives a figure for how common it is in today's lifters.
Sources 13, 14, 15
Tears: the pec and the bicepsEmerging evidence
A torn pec tendon happens almost only in men, mostly in weight training and often as the bar comes down in a heavy bench press: of 365 published cases, 83% came from indirect force and 48% happened in weight training. The American Academy of Orthopaedic Surgeons lists a pop or ripping feeling, bruising on the chest or inner arm, weakness pushing, and an uneven chest, armpit curve or nipple.
A torn long head of the biceps causes sudden, sharp pain in the upper arm, sometimes a pop, bruising towards the elbow and a bulge low in the arm, and heavy overhead lifting, smoking and steroid medicines raise the risk. A biceps tear at the elbow is uncommon (1.2 and 2.55 per 100,000 people a year in two US studies, and 3 to 5 per 100,000 in the American Academy of Orthopaedic Surgeons' figure), almost all in men. It happens when a bent elbow is forced straight against resistance, and it is best repaired within the first 2 to 3 weeks.
Sources 16, 17, 18, 19, 20, 21, 22
The heart, a clot and muscle breakdownStrong evidence
The heart doesn't care which way your arm moves. Heart attack pain is often tight or squeezing in the chest and can spread to the arms, neck or jaw, with breathlessness, sweating or feeling sick; angina is pain or tightness in the chest, neck, shoulders, jaw or arms that comes on with exercise and eases after a few minutes' rest. In 12,461 people having a first heart attack in 52 countries, physical exertion in the hour before was linked with about 2.3 times the odds, in men and women of all ages.
Rarely, heavy upper-body training is followed by a clot in the arm vein, with the whole arm swollen, throbbing, red or blue and warm; the NHS lists gaining a lot of muscle and repeated arm movements among the causes, and a review says it is best treated within 10 to 14 days. Muscle breakdown makes the muscles far sorer and weaker than the session explains, and the pee dark.
Sources 23, 24, 25, 26, 27, 28, 29, 30
When a scan or test helpsStrong evidence
Soreness, rotator cuff pain and AC joint pain are diagnosed by examination. Scans find a lot in shoulders that don't hurt: in 96 shoulders without symptoms, 34% had a rotator cuff tear on magnetic resonance imaging (MRI), none of them full thickness under 40 but 28% over 60, and AC joint changes are common in shoulders without pain (very low certainty).
Tests answer specific questions: an X-ray after an injury with a changed shape; an ultrasound or MRI scan for a suspected pec or biceps tear, which is time-critical; an MRI for weightlifter's shoulder that isn't settling; an electrocardiogram (ECG) and blood tests for a suspected heart attack; a scan of the arm veins for a suspected clot; and blood and urine tests for suspected muscle breakdown.
Sources 31, 32, 33, 15, 20, 23, 27, 29
How it usually goesStrong evidence
Soreness is gone within about a week. Rotator cuff related pain improved a lot over a year in every group of the largest trial; an NHS booklet says about half 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, though NHS inform says many shoulder problems settle within 6 weeks. Most people with weightlifter's shoulder recover with changed training. A complete pec tendon tear or a biceps tear at the elbow is a surgical decision with a time window. No one can promise a date.
Sources 1, 34, 10, 8, 35, 15