I have considered sets and reps. The traditional view on training predominately ST muscles such as the abs and calves (actually just the soleus) is to use high reps (12+ reps) because ST fibers do not fatigue as quickly as the FT fibers. Underlying this recommendation is the assumption that fatigue causes hypertrophy. Dan Moore has done the reading and, if you follow his review of scientific literature, it is not fatigue but mechanotransduction - the effect of mechanical strain - that initiates the hypertrophy response. Examined in this light it is possible to see how the old school recommendation came to be gospel: a high-fatigue muscle can perform more reps than a lower fatigue one and each rep causes mechanical strain. I am not advocating 20 rep weighted crunches only offering an explanation of how the idea got started.
In my view, the 20 rep suggestion is as valid as Colby's HST one because both recommendations derive from some manner of reasoning and/or research. Neither has been definitively proven and each has users who swear by it. The only thing to do then, is to pick one be it HST, Max-Stim, 20 reps, 3 x 10s, whatever, and do it persistently for a length of time to determine its effectiveness. This is not the miraculous for-certain advice we sometimes look for but it is the only way to find out for sure. As Byran Haycock has written and will likely tell you the individual responses to exercise of advanced trainees varies widely. I have experienced this a little bit and am slowly becoming a believer.
That being said the question now becomes how to find the set/rep and method scheme that you will respond to. Obviously you may find it following whatever program you try next. Its happened to me for some body parts. Barring that there are three ways we can determine the efficacy of a program no matter what:
1. Strength.
2. Visual observation.
3. Measurements.
Strength is part hypertrophy, part CNS. If you are getting stronger then to some extent you are getting bigger.
Visual observation is universally used but it is the least reliable. We are prone to self-deception. The use of pictures taken at regular intervals - be it daily, weekly, or monthly will show you where you are going. Another option is to have people comment on your physique. Use the same people and ask them separately what they think. A consensus is a good indicator. When it comes to abs Colby is right - you've gotta get down to where you can see them. How can you measure the progress of this very visual body part otherwise? This means that you will have to cut which means no bulking. There are trade offs. Are there not trade offs elsewhere in your life? Pick one.
Measurements. Like every other metric of progress it should be done regularly. Obviously its difficult to measure abs.
My system boils down to this:
Step 1. Make up your mind that its abs you want.
Step 2. Diet down to where you can see them.
Step 3. Once your body fat is stable and you can see your abs, asses your current ab training - not with a mirror but with a camera and/or your personal judging panel.
Step 4. If its not working change it. What to change it to? Pick something. Get an ab book. Ask someone else what they did. Try a program you think makes sense. The point is to experiment because once you find it, hell yes, you've got it.
Step 5. Determine how long you'll give this new method to produce results. Stick with it until then.
Step 6. Reassess. If it didn't work, try something else.
Here's how mine recently went, gleamed from notebooks and memory:
1. Ya ok. Abs. Lets do this.
2. No problem there.
3. Ah crap. I don't have a camera and I'm low on cash. I'll just have to use my room mate.
4. Last ab work I used a Nautilus crunch machine. I maxed it out. Still no amazing abs. It was not the right thing. Did a bunch of reading. I think ball crunches will be fine. Looks like you can really arch backwards and get a good stretch. I'll give this a shot.
5. 6 weeks.
6. Week 3 - this is becoming a pain. I'm crunching dumbells I can't yet curl and the weight on my chest is making my injured shoulder hurt more. I cannot progess with this. Time to find something new.
back to step 4: ta da! Standing crunch pulley machine in the nether reaches of my gym. Form looks good. Lots of weight on the stack I can't yet lift - there's room to grow. I'll go for 10 reps using a 4 second positive and 4 second negative. That's old school HIT.
Step 5. 6 weeks.
Step 6. Week 4 - I cannot progress steadily in strength. One day I can add 5 lbs to the stack the next day I can't. I am failing mid-way through the set and dropping the weight to make the reps. For some reason I am adding a set of lighter 10's.
Week 6 - some change in appearance noted by myself and room mate. Looking back at my notebook I've noticed that when I do the drop-weight thing I can come back the next workout and complete 10 reps with the target weight. I have made notes about form sometimes lacking. Be sure to pay attention and do the lift the exact same way every time. All of this gives me an idea: progress the weight every other workout. Go for 10 reps for the first workout. Then see how many reps I can go the second. Add weight on the third and repeat. Time will bear out a pattern. This is classical progression. Looks like I was adding too much too quickly.
Back to step 5: 6 weeks.
If you're prone to overanalysis like me you'll find all sorts of variables to wonder about:
Why 6 weeks?
>Could be longer I suppose. Maybe it should be 8. Or 10. Or 2?
Your TUT is 80 seconds, is that the best? Does it matter?
>No idea. I used to do TUT style training and 60s was the sweet spot much of the time.
Why 10 reps?
>Everyone does 10 reps!
Why a 4s pos and 4s neg?
>Read it in a book. AND it keeps me from jerking the weight.
Hey, those aren't brilliantly researched reasons.
No they are not. But I had to start somewhere.