My work with equitation students often includes some time without stirrups. As they start at the walk I may say, "Drop your stirrups, show me your two-point position down the long side for as long as you can hold it then sink back into a full seat and pick up your stirrups without looking."
The key to good work without stirrups is to try to maintain your leg in the same position as when you are riding with stirrups. This work also develops muscle memory and reminds you to keep a connection through your whole leg. If the work without stirrups is going to be more than just a couple of minutes, I have my students cross their stirrups over the withers to prevent banging the horse's sides.
To begin work without stirrups, stretch your leg down while your horse is standing still and point your toe at the ground while you feel your crotch and your seatbones connecting with the saddle. Wrap your whole leg around your horse, then position your leg by first lifting your toe up until your ankle is angled as if your toe were in the stirrup. Next, draw your knee up without pinching so that your whole leg stays connected.
When posting without stirrups, keep your leg in position and let your horse's movement push you out of the saddle, then use your leg to push yourself a little more. This will involve a lot of your thigh muscle because you need to close your hip angle somewhat and post "toward the horse's ears" as the old horsemen say--and you also need the control to avoid bouncing back down into the saddle too soon.
1. My professional, Laurel Tinney, is riding Crusader, an accomplished 12-year-old warmblood equitation horse owned by Cavallino Farm, without stirrups. When you're working without stirrups and moving up from walk to trot, it helps if you can keep your horse in a nice steady trot like this.
2. Laurel needs her good base and secure seat to stay with Crusader in sitting trot without her stirrups. She has her knee pushed well down to keep the front of her thigh on the saddle. Her hands are nice and low, and I like her angles here: Her hip angle is not closed, but her shoulder is slightly in front of her hip and her elbow is bent for an elastic contact. She's relaxed, not rigid.
3. Here Laurel is working in a half-seat rather than a true two-point: Her crotch is still touching the saddle. A true two-point is more out of the tack than this. A half-seat is less difficult to maintain without stirrups than a real two-point, and just as beneficial--it still works the same muscles.
When working without stirrups, build up the time gradually. It's a matter of pushing yourself, but not pushing so hard that you end up balancing on the reins. If you push too hard you may also end up working the incorrect muscles.
Signs that you need to take a break: You find yourself grabbing your horse in the mouth to keep your balance, you have trouble controlling your posting or you have difficulty keeping your seat secure and feel as if you might slip off. Stop for the day and try a few more minutes without stirrups tomorrow.
Want more exercises? Read Kathy Fletcher's article "Strengthen Your Base" in the August 2008 issue of Practical Horseman.