During the school year (I'm a teacher) I do a lot of my training in mini-sessions throughout the work day during breaks in my office. I can often accumulate quite a bit of volume over the course of a day or week without it getting in the way of my work schedule and without ever breaking a sweat. It's a great way to train if it fits into your circumstances.
My mini-sessions are either part of a structured program, or at least a structured daily plan (e.g., "I'm going to do sets of 3, 5, and 7 double front squats today). For instance, I might be doing a structured program for C&P and doing Q&D for ballistics. So I'll just spread out my total sets or total time for the C&P program on days when I do that, and I'll do Q&D in blocks of 1-4 series at a time (I will sometimes do more than 5 total series, occasionally substantially more, in the course of a day).I just think of the short sessions as "spreading out the work" (SOTW®©), and it can apply to many types of programs, although not necessarily with exactly the same effects as doing the programs in a longer continuous session.
Two dimensions that this kind of training is missing are sustained repeated efforts and low intensity sustained cardio. So that's what I usually do on weekends. For instance, I might do some combination of Nordic walking or the NordicTrack skier, Q&D snatches with 015 timing (10 x 10 starting a set every 3:00), and clubbell swinging. Those aren't the only possibilities, but just some examples that don't lend themselves to mini-sessions during the week.
I'm at a point where logistics and maintaining continuity of the training process trump all. Once I'm done with my work day, I'm pretty mentally and emotionally spent, and if I don't get my training in during the day somehow, I'm probably not going to do it afterward, although I might throw in a few sets of something I don't have the equipment for in my office, such as ring pullups or dips.
"Do what you can, with what you've got, where you are" (attributed to Theodore Roosevelt, but he himself attributed it a Bill Widener of Widener’s Valley, Virginia).
