I had a serious leaning problem 2 years ago when my "mare in the pair"
started to lean horribly on her brother, to the point where he had to lean
back to stay upright, and then of course it dropped her right out of the
traces so he was pulling the whole works alone. It turned out she had some
muscle issues in her hind end, and with rest and serious deep myofascial
massage (which continues today) she stopped the leaning. It seems that
work in really deep going re agravates her hind end issues, (like the mud at
Fair Hill in fall of 2004) but with regular muscle work and thoughtful
conditioning she stays happy.
The leaning reared its silly head again though. I think part of it now, when
we switch sides, is a little bit of fear as we go up the road with her on
the left (inside). She leaned like a madwoman going down the road to a
grassy schooling area. When we got there, I drove LOTS of Hardy's figure 8's
until they were working well and both upright and bending. Time to go home,
and guess what, wow did she have a temper tantrum and lean again. And the
peculiar thing is, this pony drives fine single, and in the lead of the
tandem, AND she started out driving on the left with her father in the pair.
Dana in SE PA, where it had the temerity to SNOW this morning.