Wall Chairs

I, at the beginning, I could do a wall chair for three minutes.  After a little while, I got to four.  It was all in the same day.  My legs ached the next morning.  After a few days, it healed.  Today, I beated to five.  My goal is to get to ten minutes.  Right now, I am half way through.  My legs are shaking right now.  My mom told me and I could feel it.