You can see an obvious and strong Chi reaction at LI 4. This is a very clear and rare sign of energy arriving at the point. This happens when the needle hits very precisely at the point with appropriate angle, depth and way of manipulation.  

I appear to on this short film "many hands of Tai Chi" done in Vancouver Island. 

Tai Chi 74 form at a glance

In my class, demonstrating scalp acupuncture