Mike Boyle doesn't like pistols. I respect Mike very very much.
I like pistols. I see different benefits in them.
Mike's comments on the two are as such:
"One leg squats should not be confused with pistol squats. I see this happen all the time. We (MBSC folks) talk about one leg squats and, the conversation immediately turns to pistols.
Let me be very clear. We neither do nor endorse pistol squats. Although these two exercises seem very similar they are not necessarily interchangeable.
In a one leg squat there is significantly less stress on the hip flexors and subsequently less stress on the lower back than in a pistol squat.
In a one leg squat the non-working leg is not required to be parallel to the floor and, various set up options can be used. This decreases the use of the hip flexors and decreases the potential for back pain.
A pistol squat is generally done standing on the floor and, in my opinion, can be more a circus trick than an exercise. Have you noticed how people love to be able to show you that they can do a pistol!
I must admit, being able to do a pistol is a nice party trick but, in my mind it is not great training."
I am interested by Mike's comments about stress on the hip flexors. Yes, they are isometrically contracted in an inner range, but I personally don't see that as a stress to be worried about. I respect that Mike's years of experience will shed light on whether such an exercise translates to movement problems or injury - I suspect, since he doesn't use it or endorse it, that there isn't an experience-based correlation between pistols and movement problems or injuries, at least not anymore. If that's the case, that there isn't an experience-based link, then I'm ok with basing a decision not to use them based on what effect high stress on hip flexors will do. Mike suspects that high stress on the hip flexors leads to high stress on the low back.
I've never had an individual suffer acute nor subsequently delayed low back pain due to a pistol, so I can't agree with an experience-based association between pistols and low back symptoms. Low back stress is not the same as low back symptoms, but I'm also content with stress on the low back in a pistol.
Each exercise should either reveal something about the individual, or produce something in them - that's my definition of a functional test/screen/assessment - that it reveals some minimum levels of competency to respond, then adapt to internal and external stimuli - or that a functional exercise produces some increase in ability to respond, then adapt to internal and external stimuli. In the case of a pistol, it is both revealing, and in my experience, productive of improvements in single leg force production.
Mike's preference is to leave the other leg out of the single leg squat - that is understandable - but I see reasons to leave it in.
Dr. Mark Cheng first showed me a pistol....great trick, according to Mike Boyle..... and I haven't lost my respect for them since them. Mark does a nice intro to pistol progressions and how it relates to the FMS, what's required and how you might get assistance to get a pistol right.
Mike Perry does a very good job of introducing people to their first pistol, also.
The straight leg out in front reveals minimum levels of straight leg raise patterning.
The straight leg out in front creates high levels of activity in the trunk-pelvis-hip, not dissimilar to Frans Bosch's concept of hip lock in stance phase of running or jumping.
The straight leg out in front might even create overflow or irradiation to the opposite side - the cross-withdrawal reflex is an example where a strong hip flexion stimulus is associated with a reflexive strong hip extension stimulus on the other side. In the cross-withdrawal reflex, it's due to the reflexive noxious stimulus, usually. In a pistol, it may be that a competent strong hip flexion is associated with a reciprocal hip extension stimulus on the other side. It may be. Certainly, the strong requirement for hip flexion may even trigger the opposite side hip abductors to hitch the pelvis - given that abduction is associated with an extension pattern, the addition of hip flexion may promote an extension pattern on the other side.
I said earlier that the pistol reveals more to me. That fine tunes programming of deficits. I concede that the single leg squat may reveal enough to Mike.