There was a headline a few years back in the New York Times about one minute of exercise reaping the benefits of 45 minutes (https://well.blogs.nytimes.com/2016/04/27/1-minute-of-all-out-exercise-may-equal-45-minutes-of-moderate-exertion/). The hubbub was from a study conducted at McMaster University. Long story short, intensity and strategic progressions make a greater impact than duration. My recent experiment confirms this.
For 9 weeks I limited my "workouts" to a single set of pullups performed in between my coaching appointments on Monday, Wednesday, Friday. At the very end, I was performing about 40 pullups per hour over the course of 10-12 hours. This added up to approximately 45-60 seconds of effort per bout, usually spread over ten sets, totaling up to about 9 minutes of effort on Monday, 9 on Wednesday, and 9 on Friday. It aggregated to 1,200-1,500 pullups per week.
Several interesting things occurred. My hunger increased for one. So, although I had planned on cutting weight, I couldn't pull that off AND recover from the intensity. I gained muscle, not just in the back and arms, but everywhere. And I cut body fat, while EATING MORE than I thought was prudent.
My typical eating schedule is long bouts of fasting, to which I still adhered as best I could. But with this practicum, by midday I would have to consume fairly large quantities to recover from the 400 pullups I'd performed that day or the prior. Ultimately, I was focused on achieving 40 or more pullups in a single effort, though I ended up only getting 30 (https://www.instagram.com/p/Bm4qlGelI7O/?hl=en&taken-by=jonathan.watters).
It's actually quite simple, though not easy. My weekly workout volume increase while subtracting out the time I'd normally spend on workouts. Consistency and strategic progression begat some fairly impressive results all around. Work increased while perceived effort decreased.
People who don't work at a gym or studio may scoff; but I've implemented this same strategy with clients who have no equipment. One of my distance coaching clients in D.C. is down 30lbs or so just from daily mini-exercises and protein consistency over the past year. Some body weight squats and wall/desk push-ups go a long way when you do only 5 per hour times 8 hours times 5 days times 50 weeks.