They say you can experience the heat you experience in the exercise as "burning the bad karma" out of you -- in Western parlance I interpret this as burning the unnecessarily held tension out of you and also the lack of wakefulness/strength in stabilizer muscles out of you dash. When I first did this exercise it was in a park with a bunch of 70 year old ladies. They held each position for 20 minutes. I was sweating and barely making it as as a strong 19 year. I realized my challenge was not a matter of strength but rather of Letting Go the unnecessarily held tension – forces in my body that were fighting my own intentions. As I persisted through about the 4th minute, I felt a huge release, and suddenly everything felt much light and I felt as if I could hold forever.