What the bench press asks of the lower back, and what no study has measuredEmerging evidence
You lie with your head, shoulder blades and upper back, and buttocks on the bench and both feet on the floor: the five points of contact coaches teach. Your lower back keeps a curve while you lower and press the bar. Researchers compare a flat back, which keeps your natural curve without adding to it, with an arched back, which adds to the lumbar curve and pulls the shoulder blades back. The arch shortens the bar's path: it travelled 28 to 47 mm further with a flat back in 15 strength athletes. In 20 experienced men, the arched set-up worked the large back muscles (the lats) more and cut the overall load on the shoulder by 8%.
No study has measured how the lower back moves or how much load it carries during a bench press, and none counts back pain caused by benching. A review of 39 studies of powerlifting injuries found bench press reports of torn chest muscles, broken collarbones, ribs and arm bones, shoulder dislocations and tendon problems, and no spinal injuries. So the map on this page comes from lab studies, injury surveys, cadaver studies and guidelines.
Sources 1, 2, 3
Who gets it: lifters' backs often hurt, but the bench is rarely where it startsEmerging evidence
Across the weight-training sports, the spine, shoulder and knee are the commonest injured areas. In powerlifting, the lower back made up 30.8% of injuries where reports gave numbers; in 101 Oceania powerlifters, the shoulder was 36% and the lower back 24%; and in 245 powerlifters, 43.3% had problems during routine training, mostly without needing a break. Injury rates are low: 1.0 to 4.4 per 1,000 hours of training.
In 104 Swedish powerlifters, 43% of injuries began in squat training, 27% in bench training and 31% in deadlift training. Low back and pelvis injuries were tied to the deadlift (about 4 times the odds), while injuries that began on the bench were tied to the shoulder. In an online survey of 1,387 gym users, 136 of the 432 who bench pressed (31%) linked it to training pain, but the survey didn't say which part of the body hurt with which exercise. There are no other figures for people who bench in an ordinary gym.
Sources 4, 5, 6, 7, 8, 9, 3, 10
The arch, the small joints of the spine and back painEmerging evidence
In cadaver spines, the small joints at the back of the spine (the facet joints) carried about 16% of the squeezing load in an upright, arched posture once the disc had lost some height under sustained load, and none in a slightly bent-forward posture; they share that load only when the spine is arched. That a held, exaggerated arch under a heavy bar loads these joints, and fits pain that eases when you flatten your back, is our reading: nobody has measured it in a bench press.
In 18 male powerlifters, arch height didn't differ between those at higher and lower risk of back pain, in a tiny proof-of-principle study, and powerlifters with and without back pain scored the same on seven movement control tests (12 against 28 lifters). So the arch isn't shown to cause back pain; it is one thing to change if yours hurts.
Sources 11, 12, 13, 14
When a scan or test mattersStrong evidence
Not usually. The National Institute for Health and Care Excellence (NICE) says don't routinely offer imaging for low back pain outside specialist care. In 3,110 people without back pain, disc bulges showed on scans in 30% at age 20 and 84% at 80, and disc wear in 37% to 96%, so a scan report has to match your symptoms.
Tests matter with the warning signs: a young lifter whose pain is worse arching back and doesn't settle (a possible stress fracture of the spine), leg weakness that is getting worse, or sudden new back pain after a minor strain in someone at risk of thin bones.
Sources 15, 16
How it usually goesStrong evidence
No study follows back pain from the bench press. In new low back pain, average pain fell from 52 to 23 out of 100 within 6 weeks, to 12 at 26 weeks and 6 at a year, across 33 groups of people (11,166 in all). The NHS says back pain usually improves within a few weeks but can sometimes last longer or keep coming back.
In Swedish powerlifters, 70% had a current injury, but only 16% of them had to stop training completely; most changed their training instead. No one can promise a date.
Sources 17, 18, 9