For a horse, can this be changed/improved?

Question

can long or weak longs/weak coupling be built up with the right training, or is it something cant be worked on/improved?

Answer 1

Developing the haunches, back and abdominal muscles helps, but it's hard for the horse to collect because it can't coil the loins and elevate it's back.  It is really hard to make an athlete out of a horse with long weak loins and is better to use the horse for pleasure riding.