Aside from big arms, there's no desire among aspiring underweight muscle building enthusiasts that quite outdoes the longing for a big, well-developed chest. And why not; big pectorals command respect. They're somehow primitively associated with courage and assertiveness. When you have pectoral muscles that only slightly protrude beyond your abdominal section, you're considered to be "in shape". What's more, in a world of male competitiveness where one's height seems to unfairly monopolize the aura of dominating physical stature, powerful pectorals can be a great equalizer. They tell the world that regardless of the level your genetics had you lengthened, you're packaged physical prowess by choice. You exude strength and athleticism with well developed pectorals.
Building 'big chest muscles' often requires isolating the fast-twitch muscle fibers with heavy exercises of six repetitions.
So what's the best method for developing a big chest? Well, that shouldn't be our only question. For if the pectorals aren't built in a balanced manner, excessive size can contribute to a feminizing effect on the male torso. Does anyone really want to develop "man boobs"? I didn't think so. Therefore, it's imperative that we make our pecs just a little bit top-heavy (upper pecs that protrude slightly more than the middle pecs) in our bid to increase chest size. An emphasis on making sure we are successful with incline exercises will ensure good upper pectoral development.
Notice I didn't recommend doing "a lot of incline exercises". Instead, I mentioned making sure you're 'successful' with your incline movements (this goes for all bodybuilding exercises). Although this might sound like a subtle play on words, it's really a vital issue for your muscle building progress. Overtraining is probably the biggest setback most natural bodybuilding enthusiasts unwittingly engage. Thus, you might need to add more incline bench movements to build bigger upper pecs, or you might need to lay off of those movements. It really depends on what you're currently doing. Just keep in mind that many times our enthusiasm to make progress on a particular body part leads us to inadvertently overwork that area - resulting in the exact opposite of our desired effect.
As a lifetime natural bodybuilder, nothing has done more for my pectoral development than taking emphasis off 'pressing movements' and putting it on 'flye movements'. The widespread notion that you "have to bench press" and "bench press heavy" has only been outdone in holding back pectoral growth by the practice of over training. Combine the two with the typical plights of the natural bodybuilder and you have a scenario in which pectoral growth is almost nonexistent for too many gym-goers. If heavy bench pressing were the key to a great chest, we'd see power-lifters epitomizing pectoral development. As it turns out, some of them have big pecs and some seem to have nearly none - despite the fact they can bench press heavy.
What if you could do heavy flyes? What if you could get on an incline bench and strictly move seventy-five pound dumbbells from the top of the movement - slowly down to having your arms outstretched and the weights parallel with your head (elbows only slightly bent) - and back up to the top position without any arm movement? If you can't do that for six to eight repetitions now, but you can do it a few months from now, I'd bet on your pectoral muscles being significantly larger after those few months. Making strict and heavy flye movements into the cornerstone of your chest routine can work wonders for the growth of those muscles.
Besides changing bench pressing movements to a secondary position and flyes to the primary one, I've also accelerated my pectoral gains by splitting my first flye movement into two partial rep exercises. So when I get to the gym to start my chest routine, I head straight to one of those pec/flye machines in which you hold the handles with your arms extended (only a slight bend in the elbows). These are the kind of pec dec machines that are also used for rear deltoid exercises. I adjust the seat on the machine so that a flye movement done on the apparatus will hit squarely in the middle of my pecs.
I then proceed to do two different exercises with this machine; one for my outer pecs and one for the inner. For outer pectorals, I move my arms from the fully outward position to about halfway through the range of a full flye. I do about five to eight sets like this. For inner pecs, I go from about the twenty degrees angle (where I ended my rep for the outer pec movement) to the point where the handles make contact with each other in front of me. I do those for another five to eight sets. When I'm done with these two partial rep exercises, my entire chest is worked and pumped to the max.
It's important to know that working the middle chest muscles actually brings the upper and lower pectorals into play. However, isolating the upper chest with incline movements does not bring the middle or lower chest muscles into play. The same goes for isolating the lower chest with declines; it only works the lower pectorals. Therefore, the most efficient way to begin a chest routine is with an exercise that hits the middle chest. My suggestion is that when you begin your pec workout with the above-mentioned exercise, be sure to adjust the seat so that you're hitting the very center of your chest.
Only when I've sufficiently pre-exhausted my pectorals with the strict performance of these partial-rep flyes do I go on to isolate the upper and lower pecs respectively with three more exercises. These include incline dumbbell flyes, Hammer Strength presses, and a decline angled pec deck. I do two exercises for upper pecs in an attempt to slightly over-develop them for better balance; the dumbbell flyes and the pressing movement with the Hammer Strength machine. Presses are incredibly more effective for pectoral growth when the pecs have been pre-exhausted with flyes.
If you've been having trouble with pectoral growth, I highly recommend you switch to making flye exercises the foundation of your routine. In addition, split that first exercise of pec deck flyes into two half-rep movements. This will create maximum stress on both the inner and outer pecs - working wonders on both the size and shape of the muscles.