His primary reason for training was weight loss, but he did enjoy the many challenges that Jiu-jitsu provided. He was amazed that a strong wrestler could take someone down, put them on their back, only to be choked or caught in an armbar.
BjjBrick
Building a Strong Foundation in BJJ
This is a pretty cool read about Theodore watching his Jiu-Jitsu instructor Professor Yoshitsuku Yamashita sparing with a champion middleweight wrestler.
http://www.bartleby.com/53/59.html
“Wednesday, Washington’s Birthday, I went to Philadelphia and made a speech at the University of Pennsylvania, took lunch with the Philadelphia City Troop and came home the same afternoon with less fatigue than most of my trips cost me; for I was able to dodge the awful evening banquet and the night on the train which taken together drive me nearly melancholy mad. Since Sunday we have not been able to ride. I still box with Grant, who has now become the champion middleweight wrestler of the United States. Yesterday afternoon we had Professor Yamashita up here to wrestle with Grant. It was very interesting, but of course jiu jitsu and our wrestling are so far apart that it is difficult to make any comparison between them. Wrestling is simply a sport with rules almost as conventional as those of tennis, while jiu jitsu is really meant for practice in killing or disabling our adversary. In consequence, Grant did not know what to do except to put Yamashita on his back, and Yamashita was perfectly content to be on his back. Inside of a minute Yamashita had choked Grant, and inside of two minutes more he got an elbow hold on him that would have enabled him to break his arm; so that there is no question but that he could have put Grant out. So far this made it evident that the jiu jitsu man could handle the ordinary wrestler. But Grant, in the actual wrestling and throwing was about as good as the Japanese, and he was so much stronger that he evidently hurt and wore out the Japanese. With a little practice in the art I am sure that one of our big wrestlers or boxers, simply because of his greatly superior strength, would be able to kill any of those Japanese, who though very good men for their inches and pounds are altogether too small to hold their own against big, powerful, quick men who are as well trained.”
http://www.bartleby.com/53/59.html