I”ve worked at a big box gym for over 6 years, and continue to work out occasionally in one.
You also get to be witness to some atrocious form.
One of the more common “problems” I see with lifters in these facilities is substituting lumbar movement for a lack of shoulder mobility.
You can really see this in an overhead press. At some point in the lift, the shoulders cannot flex anymore so the lower back arches to “finish” the movement. This is not only bad, but dangerous form, as the lumbar spine is not designed to be a mover (especially under a heavy load). This form over time will produce an injury.
You can see this same faulty movement pattern in the incline chest press and wheel roll out among other exercises.
Try this exercise and stay consistent with performing it (every day) and you will see a relatively quick improvement in your t-spine extension (and consequently better form on most of your lifts).
Matt Pirtle MA CSCS