The Young Horse

the hindquarters. This same concept in principle can be done in the arena by using the whole arena and going to the furthest points such as endtoend or cornertocorner. 
This simple concept often proves difficult in application but the key is to carefully apply this method and be disciplined about not overusing your aids by applying too much pressure. You may also need the assistance of a riding crop. 
Mistakes are made in small ways. If the horse goes forward off the cue but the rider continues to ask with a grinding leg aid trying to get the horse all the way across the arena the horse will receive no release for moving out and will begin balking or slowing. Focus more on teaching soft willing cues forward and less on crossing the arena in one try. Each small surge forward even if it is only a few steps must be rewarded by releasing.
Remember circles focus a horse inward while long straight lines with rest points at the end open him up. Every warmup ride I determine if the horse has more forwardness or more balkiness and on that basis I decide what needs to be done in that riding session.
With a really sticky colt I integrate this exercise many times throughout the session and then begin to add a few circles in the middle of the arena before we get to my rest point at the opposite end. Over time I expect the horse to hold this forwardness longer before the rest point.
Over the years I have found this exercise helps sticky horses become easy to move out longterm. I am often asked if this exercise will be effective with an old school horse dulled by years of beginner riders. Yes! These horses brighten up and perk their ears