Are there any safe chest exercise you can do when you have shoulder impingement? Or should you avoid all forms of chest exercise in general?
Push ups. ONLY IF THEY ARE PAINLESS. It goes without saying that, if your feel shoulder pain during push ups or any other exercise, you should stop immediately (ignoring this puts you under risk of becoming a full supraspinatus tear).
Be careful not to flare your elbows out. That goes for your triceps too (you asked that in another thread). Push ups will work your chest and triceps.
If you cannot exercise without pain, then you should not try it. Seek a therapist. Exercising while in pain will only worsen your condition. The pain happens because the subacromial space is reduced and the supraspinatus has no room. Trying to push through the pain will eventually lead to severe damage to that delicate muscle.
If you cannot afford medical treatment, then try to rest and avoid any overhead activity with that arm, and anything that causes pain. If that is your dominant arm, learn to use the computer mouse with the other. Only after the pain has gone and is well in the past, then start exercising, but always avoiding overhead activities.
Basicly any excercise you can do 30+ repetitions without pain. For rehabilitation you want a low load and a lot of repetitions, this will get the blood flowing and help the healing process. If push ups are to hard, try easier variations, e.g. leaning against an open doorway and performing the push up movement. Adjust angle by moving your feet either closer to the door or further away until you can do 30-50 reps. 3 sets are sufficient.
Stretching also helps. Stretching is also a light eccentric excercise. Take a belt or elastic band and grab above your head. Slowly move your arms backwards till the belt touches your bottom, then reverse. Repeat 5-10 times.
You need to find what works for you, depending on the severity and manner of shoulder impingement.
For some people a flat bench press hurts but an incline one feels strangely fine. Others find that barbell work is problematic but dumbbell work doesn't cause issues.
I'd suggest some experimentation, but again this all depends on how severe your impingement is.
You could give decline benching a go. Should be less of a strain on your shoulder.
You could also try some dumb bell / cable flies.
You also want to avoid any incline exercises, these will use you shoulders slightly.
But as Mephisto said only if you don't feel any pain. There is nothing worse than re-injuring yourself and having to take even more time out.
Find yourself a physical therapist to help you if possible, as he/she will be able to tailor exercises to your particular situation.
I recently went through this. I found that I could bench (flat) if I went really light on the weight (I dropped back down to the bar only) and if I got my back and shoulder position correct. For me this is retracting the scapula (but not as exaggerated as powerlifters do) and getting my elbows in the right position (for me, at a 45 degree position). Also, lift off with the arms rather than pushing the shoulders forward.
If you play around with this, you should be able to find a combination of variables where it doesn't hurt (or just barely hurts). That's what you want.
I've also found face pulls to be very helpful to get my shoulders back. Make sure to get the shoulders back and down at the beginning of each rep.
Do a reverse grip bench press. It's a good way to open up that subacromial space and correctly position the humerus head in the rotator cuff and in fact it actually helps to decompress that joint space. It's a good rehab exercise that takes pressure off the shoulder joint and emphasizes the upper chest and triceps more than the regular bench press. Don't go too.heavy, watch videos on proper form and always use a spotter. Over time, you'll notice that you should be able to go up in weight with little to no pain at all in your shoulder joint space. Eventually over time your shoulder should be able to rehab itself. By simply switching the grip from an overhand (pronated) grip to a reverse (supinated-to-neutral) grip you can preform all kinds of pressing movements with this hand positioning in mind. I can almost guarantee that you'll feel very little if any pain and it'll start to subside over time. Hope this helps.