Fast pace I mean less rest, always use good form.
So onto the 3x10 vs 10x3.
The study goes like this. They have some guy and they also have a way to measure force production.
So lets take our favorite exercise the bench press and load it with 135 lb. and assume that 3x10 at 135 is a bit of work and maybe on the last set he goes to failure.
In the test, you find that with each rep in each set, force production starts off high, say near 150 lbs (the bar has a bit of acceleration to it and moves up rapidly) but by the 8th rep you see a dip down to 135140 (the bar is barely moving as the force exerterd is very near the bar weight). This trend is measured over the 3 sets and you can get a total volume which is just 3x10x135=4050. You can also get an average force production, which would be about 142ish pounds assuming a linear fall off in force.
Now you take the same guy (but he is fresh) and you have him lift 10x3 at 135. Note Ironman that this means the sets are easy and so you are not training at all near failure so no overtraining problem here. Anyway, you see the same trend that on the first 14 reps or so a high force production of 150 lbs exists. You rack the weight, rest a bit and go on. You complete all the 10 sets in the same amount of time it takes to do the 3x10. This means that your volume is the same and your workout time is the same. The difference is that your average force production is much higher, probably near 150 lbs. it also means that you are never training near failure and will likely recover much faster.
So now in short, 10x3 gives you all the same results in terms of volume and workout time but you have a much higher force production per rep, which means your body will adapt faster to produce higher force because that is what it's being asked to do. In the 3x10, you are asking it to produce lower force about 50% of the time, so you will not adapt as quickly.
