How to build muscle...a lot of it..??

Okay so, here's the situation: my boyfriend's sister has this horse. She's a 13-15 year old (at least that's what he said) QH X Appaloosa. She's a gorgeous horse. But I feel really bad for her. She (my boyfriend's sister) is unable to ride her - she's pregnant.

She (the horse, now) has lost so much muscle just sitting in their pasture. She has little to no muscle on her rump and absolutely zero back muscle. You can see her ribs, but not too horribly; I don't think it's from being underfed - she's one chubby horse. Haha (Can someone say "Grass belly" ??)

But I offered to start riding her for them, mainly to give her something to do, and also partly because I'm suffering from not enough horsey time. What are some things I could do/work with her on starting out to help her gain her muscle back?

Thanks in advance.

Walk and trot up hills! Or through the trails

Lots of walking and trotting definitely. That will mainly get her butt muscle back. This site, Strengthen Your Horse, explains how to strengthen a horse's back.

Trotting over poles also helps build muscles.

Going up and down hills, working transitions, and circles.

Make sure she's getting enough protein. VERY important for pregnant mares. I just posted a thread on the health forum titled protein. The second responder provided a calculator for determining if your horse is getting the proper amount.

My boyfriend's sister is pregnant. Not the mare. =) But thanks. Hehe

And actually, she had her baby last night. =D

To build back muscle, you should do lots and lots of bending! Figure eights, serpentine, circles. Lunging is great, too. Ride up hills as much as possible and do trot poles to get her leg muscles working. Trotting over cavalettis is even better. And keep her at a good working trot. Trotting builds muscle, and cantering burns more fat, so I wouldn't canter her a whole lot until she's in better shape.

Congrats to the boyfriends sister first. Second, just ride her. Do what you normally would do and then work on specific areas. Get her whole body muscle tone back up before you start really worrying about working specifically her butt or her topline. You may end up not needing really specialized excercises, general everyday riding may get her back in shape.

HA!! Holy cow I totally read that wrong. I was working a double shift that day and was bored out of my mind...doing a lot more posting than reading obviously. Now my friend who manages a barn and I are even in head spaces. She once registered her son for 1st grade as a "G" when the form asked for sex of child.

As for muscle on an actual horse, backup up...a lot of it for topline, and hills for butt muscle.

Also will depend on the horse. Horses that are lightly built will simply not develop a lot of muscle.