All I've got to say is that's incredibly strong. Are you sure about those numbers? If you weigh 200lbs, your one leg is holding up the majority of your bodyweight at the bottom of the movement, let's say 150lbs or thereabouts. And if you're holding 70lbs worth of dumbbells, that's 220 lbs on one leg, which is like squatting 440lbs with both legs. And you're saying you could do that for 17 - 19 reps? That's like superhuman strong.
Also, regarding the math, pistol squat aficionados say on their websites that being able to do an unweighted squat is equivalent to doing a conventional barbell squat with a weight equal to your bodyweight. And if you can do a pistol with weights equivalent to half your bodyweight, then that is equivalent to doing a regular barbell squat with twice your weight. On the surface, it sounds reasonable. And it is for this reason that when I first began to do pistols properly that I sought to eventually do so with weights of about half by bodyweight. So 30-pound dumbbells were not quite enough and 35-pound dumbbells were just a bit over. And, over a period of time (not very long), I was doing them.
Here's what I found. Doing unweighted pistols is easy. Well, not exactly. They're easier to do if you use light weights as a counterbalance than doing them unweighted. (Seven years later, I still can't do a proper pistol for more than a rep or maybe two with no weights because I would fall backward towards the bottom of the movement.) So doing a pistol with, say, a couple of 5- or 10-pound dumbbells feels roughly like doing a conventional barbell squat with weight equivalent to your bodyweight. I cannot estimate how many I can do at a "regular" pace, but it would be a lot. Just as with a barbell squat with only 135 pounds.
However, I can tell you that when barbell squats were my principal leg exercise years ago, I was never able to do almost 20 reps with twice my bodyweight, "breathing" squats or otherwise. My first work set would be just a bit over double my bodyweight for a small handful of reps. I would then have to reduce the weight for each subsequent set to get in a reasonable number of reps. And this was when I was at my strongest, which is not now. And so, I can tell you
definitively that doing pistols with added weight equivalent to half my bodyweight does NOT translate into doing a barbell squat with double my bodyweight. I don't care what anyone else says. (And your analysis was even an overstatement of what these other guys said.)
The mechanics are different. In fact, this is the passage in the article that I linked earlier, which criticized the pistol squat, that gave me pause:
"...In addition, they reinforce faulty squat mechanics and dysfunctional movement as you’re essentially teaching your body to collapse under tension rather than staying tight and properly absorbing force."
There
is a ~"collapsing" towards the very bottom of the movement that is very much unlike a regular squat. I didn't appreciate it until I compared it with the skater squat, which better approximates the barbell squat in feel. At the very bottom of a pistol squat there is no tension, because you're just resting your butt against the back of your calf. Not that I would remain that way or bounce back up using momentum, but it was not the same. Unlike what the author wrote, however, I did not hurt any of my joints during that time when doing the pistol as intended. (However, I did wrench my back a few memorable times when I moved heavier dumbbells too far forward as I was descending. With light dumbbells, I could have them straight out in front of me if I wanted, but I had to be far more careful with the heavier dumbbells; I learned to move them forward not even inches more than necessary to act as a counterweight as I descended.)
See for yourself.
As I had written in the past, it took me about 2 weeks of trying before I was able to do the pistol squat properly. Until then, I struggled with balance and always started falling backward towards the bottom of the movement. I tried holding on to something stable for balance rather than support, but just couldn't graduate to a pistol unassisted. Until I tried it with a couple of light dumbbells which I held at my sides and then intuitively raised them slightly as needed for counterbalance as I descended towards the bottom of the movement. And then it was like riding a bicycle for the first time without training wheels. I wondered why it took me so long to get it. Give it a try once you're warmed up and stretched and see for yourself.
