A "medium frame" is expected in all
horses being ridden in intermediate and advanced equitation
classes, while many horses are also shown to their best advantage
in a medium frame in under saddle classes. For example, a horse
that is long in its body will often appear sloppy if it is
allowed to travel in a long frame. The medium frame results in
slightly shorter steps at each gait, but what is lost in length
of step is usually outweighed by the positive results of a better
balanced horse. In a medium frame, the animal's hocks lose less
energy backward in the posterior phase of each step than when the
horse is in a long frame. The energy that would normally be lost
backward is trapped by the rider's legs and cast forward,
providing greater power in the anterior phase of each step and
enabling the hocks to support some of the forehand weight.
To collect the horse into a medium frame, you not only restrict
the backward movement of the hocks with your legs, but also the
forward movement of the head and neck with your hands (see
"How to Perform a Half-Halt" in the August 1996 index).
In response to the coordinated action of your legs and hands, the
animal will raise and arch its neck slightly, making its shoulder
carriage higher, lightening its forehand, and causing its head to
come in closer to the vertical.
The medium frame retains much of the natural flow of horizontal
energy, while channeling a portion of that energy upward,
providing lightness and balance in the horse, as well as greater
control and comfort for the rider. When a horse is stationary,
its center of gravity is located just in front of the place where
the rider sits. As the horse's pace increases, the center of
gravity is shifted increasingly forward. Through collection , the
center of gravity can be shifted backward, enabling the rider to
be closer to it and producing a smoother rider.
If you watch an under saddle class, you will usually see riders
on horses in a long frame rising out of the saddle at the canter.
On a tense horse, a rider may be trying to avoid contact with the
animal's back; but even if the horse does not have a nervous
disposition, the rider will usually rise out of the saddle to
avoid the bumpy motion caused by the horse's center of gravity
being shifted forward. He literally cannot sit on his horse, for
he is just far enough behind the center of gravity to make the
ride very uncomfortable.
Not only is collecting the horse into a medium frame beneficial
for making the rider more comfortable and for balancing a long,
sloppy-looking animal, but it is also useful for giving an
already good or excellent mover a little panache. The lighter
forehand creates a slight degree of suspension in each step,
making the good mover appear to be a much better mover than it
really is and giving the gifted horse an even flashier, floating
appearance as it moves.