Ive been doing alot of debating with team mates on this. and i was wondering what some of your thoughts are on this… ive looked on here to find answers but i didnt find any… when doing the bench press exercise do you keep your back flat or do you arch it??? 
If you use an arch while performing the bench press, it makes your chest “bigger”. Meaning that you can lift your ribcage/chest further so the bar doesn’t have to travel as far… Thus helping you lift more weight. It’s a powerlifting technique. I use it everytime I bench. I don’t know if it’s a good idea to use if you have back problems though… Either way is fine though, but if you arch it is more for leverage.
Have a look at some Dave Tate articles on Elitefts.com and T-Mag.com for bench technique.
Pulling the bar appart, driving your shoulder blades into the bench, placing your feet under your hips and all that stuff.
Stick to good form, unless you are training for the bench press specificaly,
IMO just perform the lift as to what is natural