I’ve been doing yog asana for almost 2 decades now though for the past 8 years it’s been mainly self-practise because I’ve been on the road. Recently I did some Iyengar classes which pushed me to do some postures more rigorously, and to engage certain muscles more actively than I normally do. The result has been some muscle damage/strain, though most probably only temporary, on the lower right hand side of the back, at the side below the ribs. The yoga teacher insisted, as Iyengar teachers do more than others, that the hip should not fall forward (the buttocks should both remain aligned to the direction of the side stretch) in both trikonasana and ardha candrasana.
This rigor requires a lot more work in the hip and it’s here that I am feeling pain, on just one side.
I am sure that this injury/discomfort is well-known among anatomically-minded practitioners who do these 2 postures.
This is not a serious problem and I am not unduly worried (I am certain it is only muscular) but I’d be grateful for some help from someone with factual knowledge about the issue I am talking about.