Leg extension...?

I was looking at some IM usa pics last night and noticed that some of the competitors are extending their legs a whole lot more than i thought was proper. It seems that when the pedal is at the bottom their leg only reaches it by fully extending the foot. I had seen on the web a few articles that described the saddle height was determined by sitting on the saddle and putting the heel on the pedal. I thought that the legs needed some flexing even at the bottom or the stroke…

I personally feel i could benefit from a higher saddle but havent tried it since i wouldnt want to injure my knees or something else freaky. Would i be saving some muscles and using others more by doing this?

checkout these pics and tell me what you think.

http://www.ironmanusa.com/ImageGallery/images_2004/asi_3591-539-010f.jpg

http://www.ironmanusa.com/ImageGallery/images_2004/asi_3591-539-017f.jpg

http://www.ironmanusa.com/ImageGallery/images_2004/usa2004.php?directory=.&currentPic=116

http://www.ironmanusa.com/ImageGallery/images_2004/usa2004.php?directory=.&currentPic=114