Pyramid sets feel good.

Pyramid sets with the bench press will build the pectoralis fairly quickly. Probably.

Pyramid sets feel good. At least tonight when I did one. Or part of one. I routinely do two bench press sets of 15 reps at 105 pounds. This means I lift 105 pounds 15 times and then I rest for a couple minutes before repeating. I've been doing this over and over, month-in and month-out, and my pectoralis is no longer sore after these workouts (I do other weightlifting exercises, too). This means my pectoralis muscles are not being challenged, and they will not get stronger or bigger unless I work them harder. So, I changed things just a bit. I did my normal first set of 15 repetitions at 105 pounds. Then I went on to do a different exercise (1 set of dumbbell shrugs at 22.5 pounds). When I was done with the dumbbell shrugs I went back to my weight bench and did a set of bench presses using 110 pounds instead of 105 pounds. I am always afraid of hurting myself, so I never change things drastically from one day to the next. If I wanted to challenge myself a bit more, I would have continued to do a third set and then a fourth set of heavier and heavier weights. Each successive set would contain fewer repetitions until I got the point where I couldn't do more than 4 repetitions. I didn't do this tonight but maybe I will later this week. Even doing this one partial pyramid set, I could feel the additional effort being generated by my muscles to lift the extra 5 pounds and I'm pretty sure that tomorrow I'll be a little sore.

Pyramid sets seem to be a good strategy for building muscle mass fairly rapidly. This is because the pyramid sets purposely and progressively fatigue larger and larger motor units (groups of muscle cells that contract together) as a person lifts heavier and heavier weights. The large motor units are predominantly the fast-twitch fibers that can generate a lot of power but fatigue quickly. Fatigue could lead to one of two circumstances that promote muscle hypertrophy (growth in size). First, as one lifts heavier weights, microscopic tears may occur with in the muscle cells. The repair process adds protein myofilaments (actin and myosin) to the muscle, causing individual cells to expand and become stronger. Second, even if no microdamage occurred, the muscles that became fatigued did so because they temporarily ran out of stored glycogen (which can be converted to glucose and ATP to power the muscle contraction). Muscles will grow in size as the body replaces and augments the glycogen stores. 

I apologize for the technical stuff above, but I just gave a lecture on this to college students so it is fresh in my mind. My understanding is based on material found in the Exercise Physiology textbook I use, as well as in another book (at the office!) which I will reference later. I should also give credit to Davey Wavey for the pyramid set technique. Davey's fitness site is full of good material and worth browsing. I should note that Davey is gay and his appreciation for the male body is very apparent; however, even straight men like me will laugh at his sexual humor. And don't we all want better bodies?