Hey hey Cam!
Nice questions. For the head-to-toe, note that this 'just a single set for each' refers to if you are also performing preceded by one or both of the 'Dorsiflexion development' drills: https://www.movemorevrl.com/videos/ankle-dorsiflexion-development and ALSO 'Unilateral Good-morning pulses' https://www.movemorevrl.com/videos/unilateral-good-morning-pulses , all for up to 100x pulses ea. side (a capacity-benchmark for the drill). It's not necessarily just the more pulses, the less sets. It depends what you need, namely "where you are" in your stage of range-development as well as what else you have included in wider programming toward these ends . Once you have 'H2T', for example, you can keep it "alive" for just the 100x pulses ea. (hitting full H2T) as little as 2-3x per week.
The perspective is that either dorsiflexion or unilateral hinging-range will be the limiting factor for 'H2T' gains, so those two drills (Calf-pulse & GM pulse) get you to your end-range there, and THEN you "plug it in" to the last set, the 'H2T' pulses - at that point, just a single set will be sufficient stimulus. You can even practice this up to DAILY, as long as you don't experience any inflammation at the site of the tendons (high up in hamstring, behind knee, or Achilles) from all the ballistic pulsing.
Increasing FREQUENCY is preferred to increasing sets when it comes to BODYWEIGHT range-development, as we use bodyweight more from the perspective of "accustoming" to the range, which means namely encouraging the nervous system to set this as a new baseline "allowance". Think of loaded-mobility, such as the 'Jefferson curl' as the "heavy artillery" - effective, but practicing them daily wouldn't likely be sustainable. Bodyweight is then the "little & often". The takeaway - FREQUENCY trumps over VOLUME.
R.e. programming end-range work & "functional range" in general, the process follows (although nothing is fixed & each context is valuable at every stage of development):
1. Setting a new CNS baseline of resting tension, toward finding where STRUCTURAL (physical) allowance truly ends. When new to exploring a range, there is a lot of "protection" from the CNS (hypertonicity) so it's difficult to know even when our PHYSICAL restrictions actually lie. CR execution is a great method to gradually develop this, and it's low intensity is sensitive to lesions/injuries which the practitioner might not even know they have. Beginners, or anyone with existing injury, will always start here, although CR is always valuable to find your true, physical end-range (for a beginner, it could take 6 months or more to "meet" it - for an experienced person, just 1 single set of CR could take you to it).
2. Isometric/loading/strength-development - once, or whilst, structural end-range is being determined, we begin LOADING the end-range (a mix of bodyweight, and externally-loaded). This is both for the purposes of strengthening any newly-acquired range, whilst at the same time extending it (we are now literally REMODELLING the body, its connective tissues and, yes, even skeletal structure). Instead of using contract/relax in a split-form & coming incrementally deeper, for example, you might head immediately into the deepest range, and spend the full time there with extended iso. holds (e.g. 30-60" in deepest range). For strength-development, we can also include contexts which are external weight-loaded (split-squat, loaded pike, jefferson...). Their higher intensity means just 1-2x per week practice (tendons need time to recover).
3. Patterning/coordination - this is where I feel some practices, such as FRC, can fall short, namely in APPLICATION of the range to a dynamic movement context. All the 'low-gait' practices are precisely ones in which range is APPLIED, so that we experience what is BETWEEN the forms which are being developed. Ultimately, if we are to speak about "functional" range, the practice should also GIVE a function (or at at least a proposal of one). If we firstly focus on building mobility, this is now a shift to USABILITY. These patterns still, of course, provide a mobility-development stimulus (whether range, strength, or both), and can also expose any small "blind-spots" where range may not be very well "unified", and develop them (e.g. in shifting weight, changing the orientation of the body, or entering/exiting the floor).
With those ideas forward, let's consider end-range work. We want an end-range to be STRONG, but we also want it to be able to express precisely the quality which it is DESIGNED to - that is, ELASTICITY. So, if 'CR' execution "finds" the end-range", and loaded isometrics & weighted work "strengthen" both the full & end-range, then pulsing execution gives (or restores) the ELASTIC quality of that end-range. At the same time, it's still an end-range DEVELOPER too, and bouncing can take you to places which you cannot just actively "pulling", the same way as a load on your back will do in a 'Pancake' (this is why people can kick up over their head, but still have a shitty front-split). So, if working a lot of 'pulsing', I would also advise to also practice an ISOTONIC context (concentric AND eccentric) which enters & exits the end-range with STRENGTH, to ensure that it's not just "passive" range being built with the pulsing. An example would be simple unilateral calf-raises (ensuring FULL range) for dorsiflexion contexts, 'Single-leg RDL/GM' supporting the 'GM pulse', or the 'Straddle-bow/up' context for expressing strength through the ranges built by the 'Pancake' and 'MIddle-split'.
Lastly, for varied stimulus in programming I would also CYCLE these forms of execution between phases of 6-8 weeks practice - it's not linearly progressive. The progressive aspect of range-development is... the RANGE! A complete beginner using 30" CR execution to "wiggle in" to their 'H2T' would (or should) give the SAME stimulus as me doing so - we're both in our end-range. It doesn't mean I need to do more, just because I have more range. For example, for a middle-split project, you might work 1 phase all drills CR execution, next phase bodyweight iso. holds in end-range, next phase loaded iso. holds and weighted dynamic stretches, next phase focus on 'low-gait' patterns, next phase pulsing, then recycle. Intelligent programming, however, can have all these things happening at the same in different areas (e.g. CR & 'pulsing' in a 'Priority' program for greater frequency, loaded mobility in a lower-body, isometric-holds in a HS practice as auxiliary mobility, and low-gait patterns in a 'Floor-communication' practice.
Hope that gives a better overview of the perspective & proposed methodology. If anything's not clear just let me know & likewise feel free to share a video of where you're at with your 'Head to toe' in the relevant thread!
Wishing you the best in practice,
J
