USE YOUR CORE TO CONTROL THE TROT TEMPO
Many riders not only have challenges using the core to control their horse’s tempo in the trot, but they struggle with the concept of using the core when they change from posting to sitting trot.
Think of it this way. Your core should always have “tone” (positive tension).
You shouldn’t have to change anything from that positive tone in sitting or posting trot unless you’re actually giving an aid to slow tempo, decrease length of stride, or ask for a downward transition.
When you do want to change any of the three things mentioned above, contract your stomach muscles like you would do if you were exercising and doing crunches or a plank position. While engaging your abs, keep your butt relaxed.
In the beginning it might feel like quite a challenge, but being able to isolate the parts of your body is part of developing an independent seat.
To get some muscle memory, practice contracting your stomach and keeping your butt relaxed while sitting in a chair.
SLOWING DOWN THE TEMPO
Then teach your horse to respond to your engaged core by combining that engagement of your muscles with a voice command he already knows like “Slow” or “Whoa”.
Eventually you can just contract your stomach muscles without your voice to get the desired result.
SPEEDING UP THE TEMPO
To speed up the tempo, give quick pushes with your seat like you’re pushing the back of the saddle toward the front of the saddle or like you’re sitting on a swing and want to swing higher.
And then allow your seat to continue to move at that quicker tempo so that your horse adjusts his tempo to the speed you’re defining by the movement of your seat.