I think what would beat out training chest once a week or twice a week or anything like that is to really focus on HOW you are lifting the weight. 99% of people I see perform chest exercises wrong. The majority or people o most every exercise wrong but we will focus on chest here seeing as though your chest is the lagging muscle group.
First off, FORGET about the amount of weight you are lifting. This has no bearing on if your going to grow or not. Pick a weight that is appropriate. A weight that you can lift with PROPER FORM, without cheating and a weight that you PECS will be able to push. Not a weight where you triceps shoulders and back come into play. If you do this you are taking stimulation away from the pecs.
Now whether its a press or a fly or anything keep your shoulder blades pinched back and make sure your shoulders are depressed (pushed down). Also make sure your abs are contracted. DO NOT arch your back, the more of your spinal cord that is on the bench the better. And DO NOT let your rear delts come of the bench at any time and DO NOT use your front delts to push the weight.
For both presses and fly the main focus is going to be on the elbows. Forget about what is happening between your elbows and hands. This section of your arm is used to HOLD THE WEIGHT and that is it. The function of the pec is to bring the humerus bone across the chest. When it comes to presses focus in your mind on pushing the weight up through your elbows, NOT you hands. The bench press or any press for that matter if done correctly is a very short movement. And for flys bring the DBs or cable handles or whatever together WITH YOUR ELBOWS, don't pull the weight together with your hands. Remembering this will help you maintain tension on your pecs. Lower the weight and really focus on getting a full stretch and full contraction and maintaining tension on the pecs through each and every reps.
One last thing. Don't go too far down on any press or any fly. For example on a bench press don't let the bar touch your chest, keep he bar 2 inches off your chest. People will say that's not full range of motion but people need to focus more on OPTIMAL range of motion. Full range of motion is not how far you can physically travel during a movement, is it how far the intended muscle with travel from full contraction to full stretch while maintaining tension. Take bench press for example again. If you touch the bar to your chest then lift all the way up to lock out, could that be considered full range of motion? It could. But is it optimal range of motion or ACTUAL full range of motion if we look at what that actually means to us in the bodybuilding world....NO. Train smart.
