Originally Posted by County Mike
There's a good chance it's your smaller or stability muscles that are fatiguing first. Your larger muscles could be fine. Try stability workouts like rings, push ups on a medicine ball, etc. Use dumbells instead of barbells. See if that helps.
I've been doin more pushups the past week or two,but will try it using medicine ball...To be honest I'm not sure what the 'rings' are? Far as benching Ive been pretty much just doin machines,but have been getting back into dumbells the past week..