Aznewbie saidI use dumbbells the majority of time I work out my chest. Sometimes I want to do some straight up bench press with the bar. The problem is my back bows. I can't keep it on the bench.
Any tips out there?
you back bows because the weight you are lifting is too heavy. your body is trying to gain a mechanical advantage by aligning more fibers of your pecs to the plane of movement. if the weight is too heavy, your body will attempt to move the weight at a greater decline angle from your pecs, because that way it can recruit more fibres to do work. this is why you will generally be strongest at a decline bench press and weakest at an incline bench press (unless your anterior deltoids are much stronger and are recruited in the movement).
using dumbbells is good when you are lifting alone; it is far easier to drop the weight away from you if something goes wrong. safety first, young padawan. it also forces your body to learn how to stabilize during movement much differently than using an olympic bar, although you should really add variety with the olympic bar too. it is entirely different kinesthetic input for your body to process.
i would recommend that you lower the weight and concentrate on form first. you are lifting weight, not ego. disregard any perception of others opinions of what you are doing in the gym; chances are, they don't really understand why they are doing what they are doing anyway (even the REALLY big guys), and somewhere down the line they will find parts of them hurting for "no apparent reason".
as far as putting your feet up on the bench, yes, you do lose more stability, but it also forces your core to work harder to stabilize you. i tend to do this when i lift because i also have a fair amount of tightness in my lower back from time to time and i haven't seen my massage therapist in quite a while to work it out.
i hope this helps. be well.