I can see a lot of people getting really defensive about this instead of honestly weighing the benefits vs. risks of assists, and most importantly acknowledging their own limitations. The fact that we are taught to assist at ALL in a 200hr YTT is pretty damn wild. Consider this:
1) Trauma Informed: You have no clue why someone is at your class. Lots of people come to yoga after trauma, and don't know how to say "No." Touch MUST always be consensual. How can we get consent from someone who doesn't yet know how to express healthy boundaries for themselves?
2) Anatomy Informed: In the medical community, you need a special license and tons of specific training to be allowed to touch someone and move their joints around. These would be Licensed Massage Therapists, Certified Athletic Trainers, Doctors of Physical Therapy, Doctors of Chiropractic, and so on. They all have WAY more anatomy specific training than any YTT could offer. They are tested and certified. yoga teachers are NOT certified. (Yoga Alliance is a club, not a regulatory body, and you register, you do not get certified)
3) Anatomy Informed, Pt 2: I know a ton about anatomy and I am very confident that I would never hurt someone with touch. Yet I very rarely give hands on assists. The reason is that I'm never scanning to see who can go DEEPER into a pose. I'm only ever looking for the people who's form is causing them harm of some kind, and I'll help to fix that so they get the most benefit with the least harm in every pose. I do NOT adjust people to physically move them deeper into a pose. I've done it a few times per request, and hated it. Everything I know about anatomy tells me never to physically force someone's limbs beyond their normal active ROM (range of motion). In fact, I rarely let my students physically grab their own body and place feet or hands or legs in some place they couldn't do with just their own strength. This would mean flexibility outpaces strength, and this is a recipe for injury. I think that the more you really DO know about anatomy, the less you'll want to assist with the intention of helping someone go further into a pose.
4) Distractions: Assists are inherently distracting. Yes, sometimes it's distracting you from BEING distracted, and can help you refocus on your yoga practice, but I would think that more often it would be just distracting. I think it is especially distracting for more experienced students, who are probably doing a pretty good job staying focused as it is. This one is very subjective and open to debate, but it is something to consider when giving or not giving assists.
5) As a male (but not exclusive to males) I need to be especially aware of how and why I give any hands on assists. The reality is there are a LOT of jackasses who have taken advantage of their role, and so if I don't personally feel that there is a really good reason behind physical touch, I simply don't do it. This consequently makes me much better at communicating complex movement with words. Even if you love giving assists, try giving it a rest for a while to focus on your speech and see if you feel crippled in some way. You may find a weakness you knew nothing about.
6) Touch can heal. This is true. I hear many of my own teachers in the back of my head as I write this who are getting sad and reminding me of how healing and inspiring human touch can be, and how vital it is to our emotional and social health. I totally recognize this. I think that if you've weighed the anatomy and therefore you aren't assisting to push people further into a pose, and you also actually know the student at least somewhat well (enough to have some sense of trust) then you could absolutely give assists which don't cause harm physically or emotionally. These assists can be transformational.
We must evaluate our reasons for our actions, especially when we are in a position of influence.
This post is an informal response to an article I recently read, which takes a much harsher tone than me, but says much of the same thing. It's worth a quick read, and I like to link to the sources that I'm influenced by for others who may be chasing rabbits down a hole: