If you are trying to build muscle mass the best rep range to use us the one you haven't done. I spent most of my lifting career doing very low reps with heavy weights and I built some decent size but was always much stronger than I looked. People never believed I was very strong because I didn't look like a bodybuilder, I wasn't lean and muscular, just big. I never focused on weight loss or aesthetics because as a powerlifter, how I looked was irrelevant so I just kept getting stronger at the same size. Now that I am a little more balanced (less focused) in my training I like to incorporate some true hypertrophy work . Don't get me wrong, kettlebells, sprints and heavy barbell work are still the foundation of my training, but I do like to ease up on the weight some times.
To build bigger muscles you really have to shock them and give them a reason to grow. Since most of my lifting was done in the 1-3 rep range, I have now been adding in some higher rep work to really blow up the muscles. Now I'll be the first to admit that I hate doing high rep work. I don't get off on the pump and I feel like a wimp lifting lighter weights. I want to lift big heavy stuff that freaks people out! That being said, 6-15 reps will build muscle so it has to get done sometimes.
Friday I went to the gym with the idea of doing a purely upper body hypertrophy workout. The exercises I ended up selecting were incline dumbbell presses and pull-ups (not chin-ups). Dumbbells are great for building muscle size because you have to balance the bells in more planes than a bar. For strength work I use a barbell, for size I use dumbbells and for conditioning I use a kettlebell. Pull-ups are an exercise I do all the time because nothing works my pulling muscles better except deadlifts and I love the traction on my spine from hanging. Pull-ups will stress the grip, rear delts, entire back and even your abs without any load being placed on the spine. They truly are a functional exercise and it is no doubt why you see so many athletes and military people using pull-ups as a staple. From now on ditch the lat machine in favour of a bar. The reason I chose incline dumbbell presses was to put some extra emphasis on my upper pecs to avoid man boobs! I do so much flat benching that I really try to use a different angle for other pushing movements to give my shoulder joints a break.
I know this all sounds pretty bodybuilder-ish but the fact is nobody wishes they had less muscle so it isn't always bad to train for looks! I am a big believer in keeping workouts simple so here is what I did to build my upper body:
That is pretty much it. I did about 10-12 sets of 8 reps in the press and 5 reps in the pull-up. It lasted about half an hour because I was super-setting the movements and keeping a fast. This created a great pump in the chest and lats. The reason I only did the two exercises instead of a variety of pushing and pulling movements is that I see no benefit in multiple movements in the same training session. It is better to really work two movements hard than spend an extra half hour with equipment changes and extra warm-up sets just so you can "hit the muscles from different angles." Maybe if your getting ready for the Olympia this is important but for pretty much everyone I see at the gym they just need to get under some weight and lift it.
I finished off with some curls and walked home. Pretty easy workout as I was feeling burned out from yesterday's hill sprint session. Not everyone workout has to be the greatest of all time, sometimes it is good to just go pump up or do some extra work for a lagging body part.