Wednesday Search Challenge (April 21, 2010): When did jockeys start riding differently?

I've been thinking a good deal about innovation this week--how and when do new ways of doing things take over from the old, traditional ways.  


I'm especially interested in major innovations that have to do with sports.  Dick Fosbury's radically different way of going backwards over the high jump leaps to mind as a major track & field innovation that caused a real discontinuity in high jump records.  In the same way, cross-country skiing had a huge innovation when skating passed the diagonal stride as the best way to move yourself down the snowy trail. 


But this week when I was looking through some old books I noticed that even something as tradition-bound as horse racing seems to have gone through a major change in performance.  


Here's an image of a jockey racing a horse from around 100 years ago.  Notice the upright posture of the jockey while the horse is at full run. 

But look at a more modern jockey: 

Notice the crouch?  

So... my big question for today is this:  When did jockeys switch from the upright posture to the more compact form we see today?  

For extra credit, how much of a difference does it make?  Is the change just a stylistic change, or does it really make a difference in a horse race?? 

Answers tomorrow! Search on!