Can high-rep training build lots of muscle?

Time under tension is the key

Strength = under 8 seconds and 90-95% intensity

2-3 sets with 3-5 minutes rest in between

Size = 20-40 seconds and 60%-80% intensity

Little rest between sets and supersets. Go for the burn

The most important thing is to go to exhaustion. It's easier to go to exhaustion (without a spotter) if you're doing high reps. When I was lifting in college I gained 30 lbs, mostly off of high reps, with the rare low rep day for variety.

I am willing to bet your friend is right in a certain way. High intensity efforts do recruit more muscles but low intensity efforts give your body much more reps. Reps in running is everything (see the book 80/20 Running for an excelllent overview of how this works http://www.amazon.com/80-20-Running-Stronger-Training-ebook/dp/B00IIVFAEY). I bet many of the same principles apply to any motor activity, like pull-ups. Your friend is able to do pull-ups with less muscle recruitment because he has trained his nervous system to recruit less muscles to do the same exercise. He can control his body weight better and better. If you want to get bigger this might not be the best approach. However if you want to get more efficient, have better control over your body (like an elite gymnast), higher reps and low volume for 80% of your work is probably best. 20% high intensity work to increase power and strength would then give you the quality and improvement in strength over time that might surpass other methods.

I meant to say higher rep, higher volume, low intensity reps. For pull-ups/push-ups you can keep intensity low by doing a few reps at a time with breaks in between, by not doing static holds, by not increasing leverage. For higher intensity work, do lots of reps in succession, experiment with longs holds, go slower, faster, increase leverage, etc... I argue that this kind of high quality work should only be done 20% of your total pull-up/push-up workout time.

Mister Know It All wrote:

Time under tension is the key

Strength = under 8 seconds and 90-95% intensity

2-3 sets with 3-5 minutes rest in between

Size = 20-40 seconds and 60%-80% intensity

Little rest between sets and supersets. Go for the burn

This is actually a pretty good summary of a very complex topic. Obviously different things work for different people, who respond to various stimuli differently; but (most of the) top bodybuilders tend to do (much of) their work with medium or medium-high reps. (Nothing like "thousands" of repetitions, though.)

By contrast, those training for increased strength without (much) increased size (e.g. powerlifters and distance runners) will often focus on a limited number of sets with just a few reps per set.

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FWIW I've found my lifting over the last year or two kind of interesting. While rehabbing a knee, the lower back, two hernias (one "repaired" badly), and a bum shoulder--not to mention recovering from a little heart attack--I started off with extraordinarily light weights (we're talking 3# dumbbells) and built to pretty high reps before moving the weights very slowly and gradually upward. The weights I'm using are still quite light, the reps have settled into (mostly) the 8-15 range--and I'm actually showing some muscular growth for the first time in my life (and I'm 60+ years old--my testosterone years are long past!), despite keeping my bodyweight pretty steady.