In our experience a high percentage of people have real difficulty isolating and contracting their chest muscles. Over use of shoulders and poor upper back and neck posture can make it almost impossible to properly feel and control pectoral muscles.
Here is a pro tip for finding your pecs and learning to contract them forcefully. This technique takes advantage of the little known fact of middle range muscle burn. Especially with single joint movements like the dumbbell fly you will find if you stick in the middle range of an exercise your muscles experience an accentuated feel of burn. This added burning sensation makes it a lot easier for your brain to find and identify the prime movers in this case the chest muscles. It really translates well into learning how to contract your pectoral muscles.
In this set you should choose a weight which is a little bit heavier (just a little bit ;n) than you would normally use for full range of motion (ROM) dumbbell flys. This way when you go into the full chest press action it isn’t too light. The key here is to stick with the middle 1/3 range flys until you almost feel you need to set the weights down. You will find relief as you transition into the pressing movement because you now add in a lot more help from arms and even bracing from your back.
*note the video demo is performed in incline bench position for ease of filming but it does often help because it tends to offer neck support. Those with forward rolled shoulder posture (pronated shoulders) relaxing the neck during flys and press can be tough.
Be well, be strong,
Andrew and Tierney