Thanks jobana.. Your advice is useful.
I never put in like a dart. I do go slow, and i always pull back first to make sure i did not hit a nerve. have never experienced tren cough, and dont want to as well. :P

Perhaps I am hitting the quad at the wrong spot? Is it possible?
Here's my spot, and I am having a feeling that i am doing it wrong.

Click image for larger version. 

Name:	20161206_193914.jpg 
Views:	241 
Size:	253.5 KB 
ID:	166551