Training with relatively little rest between sets can be a form of training known as Lactate Induced Training (LIT)!
Charles Poliquin was one of the first to discover the physiological fact that there's a direct correlation between the amount of lactate produced and the subsequent release of endogenous growth hormone; and we all know that growth hormone is a highly lypolitic (stimulates the release of fatty acids) and anti-catabolic (muscle defender) hormone. It's also one of the reasons why 200m and 400m runners are so lean: these distances lead to an enormous surge of Lactic acid, spanning over the entire body.
(LIT) generally relies on slightly higher rep ranges because lactate production is at its highest in sets (TUT) lasting between 50-70 seconds. So if each rep lasts 4 seconds (3 seconds eccentric and 1 second concentric), hitting the ideal time under tension for lactate production would require 12-18 reps per set.
In addition, you also need to drastically reduce the rest intervals between sets ( 30 - 45 seconds). It is also a good idea to alternate exercises for muscle groups (to increase overall whole-body lactate production), and you don't want to incorporate too much volume per muscle group.
The short rest intervals and use of multiple muscles per session leads to a significant elevation in lactate levels, which in turn increases HGH production.
This method of training can be VERY benefitial to the athlete looking to shed unwanted bodyfat OR for an athlete trying to add lean Body Mass (when coupled with HEAVY training for low reps).
JD~