To a degree as you train, you augment the ceiling of productive volume, but like I said, volume can be infinite in the sense that you can do 100 sets of 1000reps each, but there is a point where adding more volume doesn't lead to improvement, and that's why I specified productive sets.
If you do 20 sets to "blast" your chest already, then how can adding another 5 be benefitial. Its akin to runners, there is a point of equilibrium between training and recuperating, runners can run to many kms in a week for there own good, this is the same with weight training/strength training. Its the common thought of, "if 10 is good, 20 must be better." When the benefits to number of sets do not correlate in a linear fashion.
But my point about load being infinite, is that, this is a better point of contention for improvement, in that if I was able to do exercise K with 100lbs for 10reps as my max, well if in 1 month I am using 125lbs for my 10RM, I have clearly improved, and can continue to do so greatly by picking appropriate exercises, and by always striving to a) increase the load, and b)always aiming for roughly the same amount of repetitions. This reasoning goes with the physiology of muscles, in that when you try to lift a weight, your muscles can do 1 of 2 things, tear completely off the bone, or 2 adapt to the demands you are setting upon it, by getting denser and stronger.
As opposed to trying to do 20 sets, and time myself to see how fast I accomplished them or tacking on more sets, you do not see clear progress in the chosen venue, namely strength (there are many kinds of strength, in this case maximal and submaximal). Olympic Weightlifters and many other strength trainers, use percentages when they train:
100% = 1 rep max
90% =
80% =
70% = usually 10RM
60%
50% = 15+ reps.
And there are recommended numbers of reps that a trainee shouldn't exceed, because phisiologically after that point it hampers instead of helping. These are guidelines, because genetically we're all granted different combinations of types of muscle fibers, so it would most likely be give or take 1-3 reps.
good informational sites to check out for various training articles
www.bodybuilding.com
www.intensemuscle.com
www.t-nation.com
www.deepsquatter.com
"In general, most people can complete 6 repetitions with 85% of their maximum resistance, 8 repetitions with 80% of maximum resistance, 10 repetitions with 75% of maximum resistance, 12 repetitions with 70% of maximum resistance and 14 repetitions with 65% of maximum resistance."