I decided about ten years ago to test my stretching theory: if you stretch cold, you lengthen the muscles permanently, and your stretch is always there for you. First, a little background story:
(Just for clarification, in my bio it states I am a black belt in Tang Soo Do, which is a Korean style of karate. In blog entries, I will often use the generic term karate because that is the term most people are familiar with).: When I started karate, I was 15 years old, and very skinny and tight. In a few months of practice, my stretch had progressed to the point where I could get through the class and do most, but not all the skills required of me. But I was not good at them. Of the kicks, moves, takedowns, that I could perform, I needed a LOT more flexibility to be able to do them correctly. What was holding me back was my body. My teacher told me I was very tight.
I worked halfhearted on my stretching, I was most interested in the punch/kick aspect of karate. Normal for a kid like me. When I made black belt, the classes intensified, and within a year I was painfully feeling my limitations in stretch. So, I took a month off of karate practice, and locked myself in my room at home. I did three or more 45 minute stretch sessions a day, working only on the stretches I COULD NOT DO. I did them cold. I did them slow. I paid attention to what hurt. My goal was to lengthen my muscles. In one month, I could get into center and side splits, lotus and all the related lotus exercises, plow, you name it.
That was in the mid 70's. In 1997, I decided not to stretch for two (2!) years, to see what would happen. In 1999, when I sat on the floor to stretch, I found that all of my flexibility was there!!
It didn't feel that great the first time, but I could get into the split and lotus and everything else.