Hello Bob,
Since there are different styles of yoga and therefore different schools of thought regarding yoga, it is best to ask the person you have chosen to be your teacher.
That having been said, I’ll give you a peek inside my view from the perch of Purna Yoga?, the yoga in which I train, practice, and teach.
There are several possibilities. The first is that the student was properly instructed but missed, overlooked, or ignored the instruction(s). In that context the pose may have been malaligned thereby resulting in undue tension following the asana (postures) practice.
The second possibility is that the student was not ready for the posture, the level of class, or the sequence. That could be due to preparation, diet, hydration, background of practice, style et al.
The third possibility is that the posture was not properly taught (safely and effectively) and/or that the sequence was not mindfully assembled.
Without knowing what exactly you did in that session and in what order, I could not give a definitive answer. If you speak with your teacher and do not get a robust, clear answer then it may be prudent to consider if this is the proper teacher for you at this time.
gordon
