Let us assume that you have done some preliminary stretches on the 
ground.  Runner's stretches work very well (picking up your horse's feet 
only gives you minor bonus points).
Given that at the start of a ride the "warm-up" assumes more of a 
life-and-death attempt to stay mounted while Sir Steed and Madam Fastlane 
display exceptional prowess at rodeo moves, there are still a few things 
you can do to prepare your body for the long hours ahead.  These 
exercises are done gently, "softly", to lightly stretch tense muscles.  
Because you are going to be doing this on a moving object, do not 
hyper-extend anything--it can lead to extreme discomfort and an unplanned 
unseating!  As with most exercises, 2-3 repetitions may be used.
Upper Body:  specifically your neck and shoulders.  This is the area that 
gives you that collapsed, "fetal-position" frame born of terror and 
locked vetebrae.  Gently drop your chin and roll your head left, right 90 
degrees, then stretch your chin skyward, only 'til you feel a little 
tension under the jaw.  Next, roll one, then the other shoulder in a 
mini-circle forward and back.  Take nice deep breaths, rhymically, and 
exhale sloooowly.  You may feel the beastie getting just a hair calmer as 
your body begins to relax.
Torso:  this will help set the seatbones, balance you right-to-left and 
straighten your posture, and improve your ability to breathe from the 
diaphragm.  Do this on each side--raise your arm straight up as if 
reaching for an imaginary treebranch but don't lift your chin.  Keep a 
soft focus with your eyes--try to take in as much of the scene as 
possible, including all the peripheral activity--and take a deep breathe, 
exhale sloooowly.  Ride a few strides (walk, trot, canter-doesn't matter) 
this way.  Now, bring your arm to 90 degrees to your body and slowly 
rotate the arm forward toward the horse's ears, back to midpoint, then 
extend back as far as is comfortable. Do not rotate from the hip as this 
is designed to work the shoulder/trunk area. This isn't a "swinging" motion 
but rather a controlled rotation done in conjunction with slow rythmic 
breathing.  You will get no benefit from "flinging" your arm back & forth.
Repeat on the other side.  Now, place your hand on your hip and make 
mini-circles with your shoulder again.  Finish with a little neck 
stretching as above.
Alternate centering tricks:  place your hand on the center line of your 
helmut, "drop your knees", breathe deeply, exhale slowly.
What this does is stretch the torso evenly and uncollapses a shoulder 
that may have become tilted.  If you have a problem with "tilting", 
practice at home going down the trail with the arm on whichever side is 
at fault extended striaght up--do this for the count of ten and repeat as 
necessary.  Looks odd but it works!
Hips, seat, legs:  ever go "uumph" when you've reached around to 
straighten the rump rug?  You are probably locked in the torso (above 
helps) and the hips.  So, either put your hand on your hip or extend to 
the side at 90 degrees and slowly rotate from the waist back to front.  
This time allow your head to follow the motion and scan the horizon 
slowly with a soft focus as you go, inhale on the back swing & exhale on 
the front swing.
To set the seat and stretch the legs will require a) a horse that isn't 
jigging around too much and b) an act of faith on your part.  It is best 
done with dropped stirrups (act of faith) but can be done with them.  
Don't do anything to the point of pain!  Nice deep breath, hold and
slowly exhale as you stretch one leg at 90 degrees to the saddle--you want some 
daylight in the thigh area (feel the burn!).  Then slowly "swing" the leg 
forward and back, again only as far as is comfortable and repeat the 90 
degree stretch.  Next bend your leg at the knee and "swing" forward and 
back, then 90 degree stretch.  Return to normal position and feel how 
you have recentered yourself.  Nice deep breath, exhale, relax and 
with your right hand grasp the pommel and "pull" yourself deep in to the 
seat.  Repeat on the other side.  
For the "advanced", try combining the torso "swings" with the leg 
lifts/stretches.
The feet:  take one or both feet out of the stirrups and point the toe 
down for 3, then up for 3, make mini-circles clockwise, 
counterclosckwise.  This frees up the ankles and relieves the tension on 
the ball of the foot.  "Scrunch" your toes a few times--but be careful, 
sometimes this will cause you to cramp! 
Imagery helps while you are learning to do this.  Imagine yourself as a 
ragdoll, limp, placid.  The "wide-eyed" look is the soft focus, Sally 
Swift relaxation technique.  Do this comparison--stare REALLY HARD at a 
object in the near distance, scrunch up your eyes, really concentrate.  
What do you feel?  Tension in the neck, shoulders, collapsed shoulders as 
they fall forward "toward the object", shallow, rapid breathing?  Now softly 
focus on the same object but take in the entire horizon including your
peripheral vision, see everything, feel your breathing slow and your 
chest cavity and buttocks relax.
These exercises should be practiced at home, at a walk, until you and the 
horse are very comfortable with the routine.  Make this a pleasant 
experience that can have a calmative effect on your equine partner.  When 
you are extending that arm forward, why not have a carrot in your hand to 
lure your partner into a nice neck stretch back to you.  Your exercises 
will become a reward for your partner because your shoulders/neck/seat 
(buttocks) will relax and relieve tension that is communicated through 
the reins & the saddle.  If exercise=pleasant=rewards, you will find 
these to be an invaluable aid at the start of a ride and a wonderful 
restorative to your weary muscles during the ride.
The torso exercises can be done conveniently at any gait, but a 
monotonous long stretch of trotting seems a good place to do them.  Also 
when you need to walk to kill time, get control, handle terrain, etc the 
exercises will be a routine immediately recognized by your partner and 
may help to convince him that a walk, not a jig, is the right gait.
I hope this makes sense--if not I'll try to clarify.
A note on the "drop the knees" concept.  You are all familiar with 
the "heels down" command and why it is necessary (to some extent).  What 
I have found is that when I do "heels down" what I get is "foot forward" 
(I'm not 12 years old and nobody broke my ankles when I was little to get 
that classic hunter-jumper look).  So I end up in a chair seat with my 
legs forward, shoulders hunched and about as unclassic as you can be.  
Years ago my dressage instructor, Candy Clemens, gave me a different 
image--"dropped knees".  You sink deeper into the seat (after doing the 
above exercises), drop the knees and allow the leg/foot to naturally fall 
back into a proper position.  You may or may not have the heels way 
down--much depends on your particular anatomy--but the goal is a level 
foot and an "educated" leg in position to influence the horse.  You won't 
be able to do this if you are grippy in the knee or your thighs are 
velcroed to the flaps, hence the leg stretches to loosen the thigh.  Col. 
Alfred Kitts (to my mind the greatest of all dressage instructors) 
expected "loose, floppy" thighs (jiggly like jello--do watch the German 
dressage riders, look at their thighs and you'll see what I mean).  You 
can only achieve this when you have a properly centered seat with the 
seatbones in even contact with the saddle.  Col. Kitts found that women 
have a difficult time with this concept (let's face it, "jello thighs" 
doesn't float MY boat) and it took a lot of cajoling to get us women to 
warm up to the idea & try it.  It's also harder for women to achieve 
because we have natually "rounder" musculature in the thigh, men are 
flatter and can shape to the horse's back more easily--and this is 
independent of, and in addition to, the influence of pelvis width.
Hope this isn't all "old news"--many of you are probably aware of these 
exercises already.  If you need clarification, please don't hesitate to 
ask!
Diane @ Safe Haven
Allentown, PA
Mr T, Miss B & Kasey with Chef d'Equippe "Odie", the naked Newfi